Review: other group systems—Diego, Yt, Xg, Scianna, Dombrock, Colton, Landsteiner- Wiener, and Indian

K.M. B YRNE AND P.C. B YRNE

Introduction Diego Blood Group System This review was prepared to provide a basic The Diego blood group system (ISBT: DI/010) has overview of “Other Blood Groups.” Some of the more expanded from its humble beginnings to now include major blood group systems, i.e., ABO, Rh, Kell, Duffy, up to 21 discrete antigens (Table 1). 3 Band 3, an anion and Kidd, are also reviewed in this issue and are not exchange, multi-pass membrane glycoprotein, is the covered here. The sheer mass of data on the MNS basic structure that carries the Diego system antigenic blood group system is so extensive and complicated determinants. 4 The that encodes the Band 3 that it justifies a review all of its own, and it is therefore is named SLC4A1 and its chromosomal location not discussed in this article. However, various aspects is 17q12–q21. 4 of MNS were described in recent papers in Di a and Di b are antithetical, resulting from a single Immunohematology. 1,2 nucleotide substitution (2561T>C) that gives rise to The blood group systems that are covered are those amino acid changes in the Band 3 protein (Leu854Pro). that most workers believe to have some degree of To date, the Di(a–b–) phenotype has not been clinical importance or interesting features: Diego (DI), described. The Di a and Di b antigens are resistant to Yt (YT), Xg (XG), Scianna (SC), Dombrock (DO), Colton treatment with the following enzymes/chemicals: (CO), Landsteiner-Wiener (LW), and Indian (IN). ficin/papain, trypsin, α-chymotrypsin, DTT (0.2 M), and Readers will find a brief digest of each blood group chloroquine. 4 The only other pair of antithetical system, which includes some historical, statistical, antigens in the system are Wr a and Wr b, the result of genetic, biochemical, and serologic data. It was the another nucleotide substitution (1972A>G) that authors’ intention to compile data that could be produces another change in Band 3 (Lys658Glu). 4 The entitled: “Other Blood Groups: What you need to know extremely rare Wr(a–b–) phenotype has been found in for the SBB exam.” 1 persons with rare glycophorin variants, where Readers will note that there are only a few expression of the Wr b antigen is dependent upon the references used in this review. Most of the information presence of functional glycophorin A. 5 The Wr a and given here has been dissected from the books listed in Wr b antigens are resistant to treatment with the the fourth and fifth references. Between them, they following enzymes/chemicals: ficin/papain, trypsin, α- contain a much more detailed, extensive, and chymotrypsin, DTT (0.2 M), and chloroquine. 4 comprehensive review of the vast volume of material The other antigens in this system are of extremely available on these blood group systems. For additional low frequency and are usually the result of single information or clarification, readers are strongly nucleotide substitutions. Interestingly, many of the encouraged to consult the aforementioned antibodies directed against these low-frequency publications. The additional references contain antigens show some degree of crossreactivity or other pertinent newer information that has been reported serologic associations with each other, and this is often since the publication of the main sources of data. the reason why their inclusion in this blood group

50 IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 Review: less well-known blood group systems

Table 1. Diego blood group antigens and/or cause in vitro . a First Incidence (%) 5 Anti-Di has often been implicated in ISBT Conventional Historical reported 5 (Caucasians) Notes 4,5 HDN, but reports of immediate DI1 Di a Diego 1955 <0.1 S. Amer. Ind.: 36% Chinese: 5% hemolytic transfusion reactions are Japanese: 12% confused by other issues. 5 Anti-Di b Chippewa: 11% usually only cause mild HDN but DI2 Di b Luebano 1967 >99.9 there have been a few reports of DI3 Wr a Wright 1953 <0.1 delayed transfusion reactions. 4,5 DI4 Wr b Fritz 1971 >99.9 Anti-Wr a is probably one of the DI5 Wd a Waldner 1981 <0.1 Found in two most commonly seen antibodies to a Hutterite families low-frequency antigen (and is a a DI6 Rb Redelberger 1978 <0.1 particular bane to one of the authors DI7 WARR Warrior 1991 <0.1 May be unique to Native Americans during the manufacture of blood grouping reagents). It is often found DI8 ELO 1993 <0.1 in the sera of individuals who have DI9 Wu Wulfsberg 1976 <0.1 produced antibodies to other RBC DI10 Bp a Bishop 1966 <0.1 antigens. Given the extremely low DI11 Mo a Moen 1972 <0.1 frequency of the Wr a antigen it seems a DI12 Hg Hughes 1983 <0.1 unlikely that those individuals have a DI13 Vg Van Vugt 1981 <0.1 been actually exposed to Wr(a+) a DI14 Sw Swann 1959 <0.1 RBCs. DI15 BOW 1988 <0.1 Thus, many examples of anti-Wr a DI16 NFLD Newfoundland 1984 <0.1 appear to be “naturally occurring” or DI17 Jn a 1967 <0.1 stimulated by some-thing other than DI18 KREP 1997 <0.1 RBCs and, in particular, in sera from DI19 Tr a Traversu 1975 <0.1 (Provisional)* individuals who have made multiple DI20 Fr a Froese 1978 <0.1 antibodies to low-frequency DI21 SW1 1987 <0.1 antigens. Behavior of the antibodies * ISBT assignment to DI varies greatly, perhaps dependent upon the method of immunization. system was initially postulated. Most of these low- Many examples of anti-Wr a are IgM, saline-reactive; frequency Diego system antigens have only been found others are IgG, reactive by antiglobulin techniques. Still in small kindreds or isolated ethnic groups. While other examples contain both IgG and IgM these antigens and their corresponding antibodies may components. Most do not bind complement or cause have clinical significance, they have little or no impact in vitro hemolysis. Anti-Wr a has often been implicated upon everyday . 4 in HDN and transfusion reactions. 5 An altered form of Band 3 protein has been associated with a hereditary form of red cell ovalocytosis known as South East Asian ovalocytosis, Yt Blood Group System and may confer a degree of resistance to invasion by The Yt blood group system (ISBT: YT/011), often the malarial parasite Plasmodium falciparum. A incorrectly referred to as the Cartwright system, complete absence of Band 3, and, therefore, the consists of two antigens: Yt a and Yt b.6 The antigens are Di(a–b–) phenotype, was thought to be incompatible carried by a GPI-linked glycoprotein named acetyl- with life. However, a severely hydropic, anemic baby cholinesterase (AChE), which is the product of the who lacked Band 3 and protein 4.2 was resuscitated ACHE gene located on 7 at position q22. after birth and kept alive by blood transfusions. 4 The function of this enzyme in RBCs is not known, Antibodies to Di a and Di b are generally IgG1 and however AChE is a major component of nerve impulse IgG3, although some IgM examples have been transmission. 4 reported. 5 They are usually produced in response to The genetic polymorphisms that give rise to the RBC exposure and are reactive by antiglobulin antithetical Yt a and Yt b antigens are the result of a techniques. Rare examples may bind complement nucleotide substitution in ACHE (1057C>A), which

IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 51 K.M. B YRNE AND P.C. B YRNE produces an amino acid change in the AChE example of anti-Yt a was reported to bind complement, glycoprotein (His353Asn). 4 As seen in Table 2, Yt a is of but neither in vitro hemolysis nor HDN has been high frequency in Caucasians and Yt b is of moderately attributed to Yt antibodies. 4,5 low frequency. This pattern has been seen in most The clinical significance of Yt antibodies in the populations studied, although the rarity of anti-Yt b has transfusion arena has attracted a great deal of attention limited the volume of screening possible. 4,5 Studies in and has caused an even greater amount of conster- Japan indicate thatYt a may be of higher frequency, since nation. Most work has been done on examples of no Yt(a–) individuals were detected in tests on 5000 anti-Yt a, since examples of anti-Yt b are so rare. Over a donors, and no Yt(b+) samples were found among the dozen studies have been performed on a varying 70 tested with anti-Yt b.5 On the other hand, Yt b appears number of examples of antibody, using a variety of to be more prevalent in Israel, where it was found in 24 clinical significance indicators: 51 Cr survival studies, to 26 percent of individuals tested. This finding was monocyte-monolayer assay (MMA), transfusion of accompanied by a relative lowering of the incidence of antigen-positive cells, and/or combinations of the Yt a. The incidence of the rare Yt(a–b+) phenotype in above. The conclusion: Many examples are benign, i.e., Israel was estimated to be 1 in 65, compared to an not clinically significant. However, other examples estimated 1 in 500 in the United States. 5 have caused shortened RBC survival of transfused antigen-positive cells and Table 2. Yt blood group antigens at least one has caused a delayed 5 First Incidence (%) hemolytic transfusion reaction. In ISBT Conventional Historical reported 4 (Caucasians) Notes 5 5 YT1 Yt a Cartwright 1956 99.6 others, the data are inconclusive. YT2 Yt b 1964 8 24–26% in Israelis

Xg Blood Group System The Yt(a–b–) phenotype has only been reported The Xg blood group system (ISBT: XG/012) 3,6 is so once and was determined to be the result of transient a named because the gene that encodes the originally suppression of Yt in a person who was believed to be described antigen is carried on the X chromosome. Yt(a+b–). The patient produced an antibody that Until recently, when the CD99 antigen joined the reacted with both Yt(a+b–) and Yt(a–b+) cells, and a ab 5 system, Xg was the sole antigen in this system, a thus appeared to be anti-Yt . polymorphism expressed on the Xg glycoprotein, Yt antigens may be absent or have radically which is encoded by the XG (PBDX ) gene (located on reduced expression on the RBCs of persons with the X chromosome at position p22.32). The gene paroxysmal nocturnal hemoglobinuria (PNH). In product is a single-pass glycoprotein that may have particular, PNH type III RBCs lack most GPI-linked biological function as an adhesion molecule, since it and therefore may lack Yt antigens along with shows a large degree of homology with CD99, a known any other antigens carried by GPI-linked proteins, e.g., 4,5 4,5 adhesion molecule found on a wide variety of tissues. Dombrock system antigens. Since the first report describing CD99 on RBCs and The Yt antigens are variably sensitive to ficin/ its variable expression, other phenotypic relationships papain treatment, i.e., denaturation of antigen has been were noted: Xg(a+) individuals (male or female) have reported by some workers while others find them high expression of CD99 as do some Xg(a–) males, resistant or even enhanced. The antigens are resistant while Xg(a–) females and some Xg(a–) males have low to trypsin and chloroquine but can be inactivated by α- 4 expression of the antigen. This observation, and the chymotrypsin and DTT (0.2 M). more recent discovery that the structural gene that The Yt a antigen appears to be moderately immuno- a encodes CD99 ( MIC2 ) is closely linked to XG, has genic and anti-Yt is not an uncommon occurrence in resulted in CD99’s being added to the Xg blood group Yt(a–) persons transfused with Yt(a+) RBCs. Examples system. 3,5 of anti-Yt b, on the other hand, are very rare. Anti-Yt a is b The most interesting aspect of this system arises often found as a single specificity, while anti-Yt is more from its direct relationship to the X chromosome. often found in multitransfused patients who have made Because females carry two X (XX) and other RBC antibodies. Yt antibodies are IgG and react males only one (XY), the incidence of the Xg a antigen preferentially by antiglobulin techniques. At least one varies radically between the sexes. That the Xg(a–)

52 IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 Review: less well-known blood group systems

Table 3. Xg blood group antigens some other stimulatory mechanism. First Incidence (%) 5 Some examples have been reported ISBT Conventional Historical reported 4 (Caucasians) Notes 5 to bind complement, but in general a XG1 Xg 1962 Females: 89 Similar pattern seen a Males: 66 in other populations; anti-Xg is not clinically important. slightly lower in Neither transfusion reactions nor Orientals. HDN have been attributed to anti- XG2 CD99 1981 > 99%* Xg a.4,5 * Strength of expression varies according to presence or absence of Xg a The single reported example of autoanti-Xg a did cause clinical phenotype is fairly common in males and females problems in the form of severe . The indicates that a gene that does not encode the Xg a IgG, complement-binding autoantibody was seen in a antigen is also common (where Xg is the gene that pregnant woman, who delivered an Xg(a+) infant with does not express antigen and Xg a is the gene that a positive DAT. While the pregnancy may have does). Thus the exhibited phenotypes may be the exacerbated the severity of the anemia in the mother, result of a variety of genotypes: Xg(a+) women may the infant was not anemic and exhibited only mild have one or two expressing Xg a, i.e., be Xg a/Xg a bilirubinemia following birth. 5 or Xg a/X g, whereas men only have one X chromosome, on which the Xg a-expressing gene may or may not be present ( Xg a/Y or Xg/Y ). Since women are Scianna Blood Group System more likely to carry the appropriate gene, the antigen The Scianna blood group system (ISBT: SC/013) is found in 89 percent of European women, compared currently consists of four defined antigens: Sc1, Sc2, with 66 percent of men in the same geographic area Sc3, and Rd (Table 4). 7 The antigens are carried on a (Table 3). Studies on other populations (including recently identified RBC adhesion protein called human some U.S. studies), indicate that the prevalence of the erythroid membrane-associated protein (ERMAP). Xg a antigen is fairly uniform, although a slightly lower Earlier workers had identified the antigen-carrying incidence is seen in Chinese and Japanese. 4,5 structure as “Scianna glycoprotein,” which was Expression of Xg a antigen varies between individ- encoded by the gene SC. The gene is now called uals. However, strength (dose) of antigen is not always ERMAP and is located on at position related to phenotype, i.e., Xg a/Xg a women do not p34.1. 4,7,8 necessarily exhibit a “double dose” of antigen The Sc1 antigen has a very high frequency in all compared with Xg a/Xg women. Further, while some X- populations studied. The overall frequency of its linked genes are affected by “Lyonization” or “X- antithetical antigen, Sc2, is less than 1 percent, but may chromosome inactivation,” the gene encoding Xg a is be higher in some Mennonite kindreds. 4,5 The alleles not affected, therefore any individual carrying an Xg a are the result of amino acid changes in ERMAP gene should express the antigen on their RBCs. (Gly57Arg). 7 Exceptions to the normal pattern of inheritance have The Sc:–3 phenotype is extremely rare and has only been described but are extremely uncommon. 5 been described in a handful of individuals, mainly The Xg a antigen is denatured by treatment with members of fairly isolated and potentially inbred South Pacific communities. There are three reports of Sc:–3 ficin/papain, trypsin, and α-chymotrypsin, but is not affected by DTT (0.2 M). Effects of chloroquine persons who produced an antibody that was classified treatment have not been reported. 4,5 Antibodies to Xg a have varied Table 4. Scianna blood group antigens First Incidence (%) 4 characteristics. Most are IgG, reactive 4 4 preferentially by antiglobulin tech- ISBT Conventional Historical reported (Caucasians) Notes SC1 Sc1 Sm, Scianna 1962 > 99 niques, but others have been SC2 Sc2 Bu a, Bullee 1963 0.3 1% in Northern reported that were IgM and were Europeans (incidence best detected in room temperature may be higher in saline tests. Examples of alloantibody Mennonites) have been found in persons with a SC3 Sc3 1980 > 99.9 SC4 Rd Rd a, Radin 1967 < 0.01 0.5% in Danes; 0.1% in history of RBC stimulation, while Jews, Candians, and others appear to be the result of African Blacks

IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 53 K.M. B YRNE AND P.C. B YRNE as anti-Sc3. Two were from a South Pacific community, with a variety of disease states. Interestingly, one well- but the third was in a transfused Caucasian male. 4,5 The investigated example of autoanti-Sc1 was reactive only 4,5 DNA of only one person with the Sc null phenotype has in serum and not in plasma. been tested and the null phenotype was found to be the result of a 2-bp deletion in the ERMAP gene, which Dombrock Blood Group System causes a frameshift and produces a version of ERMAP The five antigens of the Dombrock blood group that does not carry the normal Scianna blood group 5 8 system (ISBT: DO/014) were described long before antigens. they came together as a group (Table 5). While it had The low-frequency antigen Rd (Radin) was recently been noted that there were serologic and phenotypic added to the Scianna system since the workers who relationships between three of the antigens prior to described the expression of Scianna system antigens forming the Dombrock system, 5 it was the exciting on ERMAP found that Rd was also expressed on the 7 finding that Gy(a–) RBCs are Do(a–b–) that linked the same protein. The antigen is the result of a mutation five antigens together as members of the Dombrock in ERMAP that produces a change in the expressed blood group system. protein (Pro60Ala). This confirmed earlier data that indicated that production of Rd was Dombrock blood group antigens controlled by a gene on chromo- Table 5. First Incidence (%) 5 some 1, in the same region as SC. ISBT Conventional Historical reported 4 (Caucasians) Notes 4,5 Immunoblotting with anti-Rd had DO1 Do a Dombrock 1965 67 55% in Blacks; shown that Rd was carried on a 24% in Japanese; protein approximately the same 14% in Thais b size as the Scianna glycoprotein. 5 DO2 Do 1973 83 89% in Blacks a However, the earlier finding of a DO3 Gy Gregory 1967 > 99.9 person with Sc:1,2, Rd+ RBCs had DO4 Hy Holley 1970 > 99.9 suggested that Rd was not an allele of DO5 Jo a Joseph 1972 > 99.9 Sc1 and Sc2. 4,5 The Sc1 and Sc2 antigens are resistant to treatment The antigens of the Dombrock system are carried with ficin/papain, trypsin, and α-chymotrypsin, on the Dombrock glycoprotein, a GPI-linked whereas treatment with DTT (0.2 M) renders the glycoprotein. The gene itself, DO, has been reported to antigens undetectable in serologic tests. Chloroquine be located at 12p13.2–p12.1 and was recently cloned. 4 treatment has no effect upon Sc2 or Sc3 and it is a b 4,5 Do and Do are the only antithetical, polymorphic presumed that Sc1 behaves in a similar fashion. The antigens in the Dombrock system. The Do a antigen, in Rd antigen differs in that the effect of trypsin and α- particular, demonstrates a wide variation in incidence chymotrypsin treatment is variable. between ethnic groups, while Do b is more consistently Antibodies to Scianna system antigens are usually of higher frequency. The other three antigens of the IgG, and are reactive preferentially with antiglobulin Dombrock system, Gy a, Hy, and Jo a, are of extremely techniques, although a few examples of saline-reactive high frequency in all populations. 4,7 The rare Gy(a–) anti-Sc2 have been reported. The antibodies may or phenotype is considered the null phenotype within the may not bind complement, but they do not cause in Dombrock system. Until recently, when a Black vitro hemolysis. Typically, these antibodies are proband was found, it had only been found in produced in response to RBC stimulation (transfusion Caucasians and Japanese. Such individuals lack all or pregnancy), although some examples of anti-Sc2 other Dombrock system antigens, i.e., their red cell appear to be “naturally occurring.” Although data are phenotype is Do(a–b–), Gy(a–), Hy–, and Jo(a–). The limited, Scianna system antibodies have not been absence of the DO glycoprotein is apparent in persons reported to cause severe transfusion reactions; in with type III PNH, whose RBCs either lack or have general, they cause mild, if any, HDN; but they may 4,5 4,5 markedly reduced levels of all GPI-linked proteins. cause a positive DAT. However, anti-Rd has caused The Hy– and Jo(a–) phenotypes are found severe HDN. Autoantibodies with Sc1 and Sc3 exclusively in Blacks. Hy– individuals phenotype as specificity have also been described and may be a Do(a–b+w), they are Jo(a–), and they have a significantly consequence of antigen suppression in association weakened expression of Gy a. Persons who are Jo(a–)

54 IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 Review: less well-known blood group systems exhibit normal Gy a antigen expression but have Co a and Co b antigens are carried on a multi-pass weakened expression of Hy and the other Dombrock membrane glycoprotein called Aquaporin-1 (AQP1) or antigens (if the genes for Do a/Do b are present). 4,5 When Channel Forming Integral Protein (CHIP-1). The gene these phenotypic observations (Table 6) and the newer that encodes this water transport protein is located on biochemical information were analyzed, it was possible chromosome 7 at position p14 and is formally called to finally rationalize the five antigens into the formal AQP1 (Aquaporin-1). The Co3 antigen is always blood group system known today. 4 present when Co a and/or Co b are expressed, i.e., the genes that encode Co a and Co b also encode for the Table 6. Dombrock system phenotypes production of Co3. The location of the Co3 antigen on Antigen CHIP-1 is yet to be defined. Studies on AQP1 have a b a a Phenotype Do Do Gy Hy Jo revealed at least six different molecular bases for the Do(a+b–) +0+++ Co(a–b–) or Co:–3 phenotype. 4 See Table 7 for Do(a+b+) +++++ antigens and frequencies. Do(a–b+) 0++++ Gy(a–) 00000 Table 7. Colton blood group antigens Hy– 0+w +w 00 First Incidence (%) 5 ISBT Conventional Historical reported 5 (Caucasians) Jo(a–) +w 0/+ w ++w 0 CO1 Co a Colton 1967 99.7 CO2 Co b 1970 9.7 All Dombrock system antigens are resistant to CO3 Co3 Co ab 1974 > 99.9 treatment with ficin/papain, they are sensitive to and weakened by trypsin and α-chymotrypsin, respectively, Co a and Co b are antithetical, the result of a and they are sensitive to DTT (0.2 M) and resistant to nucleotide substitution in AQP1 (134C>T) that leads to 4 chloroquine. an amino acid change in CHIP-1 (Ala45Val). Co a is of a b Do and Do appear to be poor immunogens. high frequency in all populations. The Co b antigen Antibodies are rarely found and are even more rarely shows a little more variation between ethnic groups, found as a single specificity, i.e., they are generally only but is generally found in 8 to10 percent of individuals. found in multitransfused individuals with a number of The Co3 antigen is of extremely high frequency. 4,5 antibodies to common antigens. The antibodies are Absence of Co3 results in the null phenotype invariably the consequence of RBC stimulation, are [Co(a–b–)], which has only been described in a handful predominantly IgG, and are reactive almost exclusively of people. 4,7 Interestingly, even though such persons by antiglobulin techniques. The antibodies do not bind appear to lack an apparently critical water transport complement and do not cause in vitro hemolysis. protein, i.e., CHIP-1, they have no significant medical a b Antibodies to Do and Do have been implicated in conditions under normal circumstances. 5 transfusion reactions but have not been shown to Antigens in the Colton system are resistant to cause clinical HDN. 4 Anti-Do a has a reputation as an treatment with ficin/papain, trypsin, α-chymotrypsin, antibody that may disappear in vivo, becoming chloroquine, and DTT (0.2 M). 4 undetectable by conventional serologic tests—a Antibodies to Colton antigens are usually the result particularly nasty characteristic more often seen with of exposure to RBCs, from either transfusion or Kidd system antibodies. pregnancy. The antibodies produced usually are IgG in a The Gy antigen is highly immunogenic and usually nature and react preferentially by antiglobulin results in production of an IgG antibody, which reacts techniques. Some examples may bind complement, a preferentially by antiglobulin techniques. Anti-Gy does but in vitro hemolysis is rarely encountered. 4,5 not bind complement and does not cause in vitro Anti-Co a is most often seen as a single specificity hemolysis. Moderate transfusion reactions due to anti- and has been reported to cause transfusion reactions a Gy have been reported, but no clinically significant and HDN. On the other hand, anti-Co b is more often 4,5 HDN has yet been documented. seen in persons with other RBC antibodies and has also been documented as causing transfusion reactions, but 5 Colton Blood Group System has only been reported to cause mild HDN. The Colton blood group system (ISBT: CO/015) Anti-Co3 is only seen in persons with the Co(a–b–) consists of just three antigens: Co a, Co b, and Co3. 5 The phenotype. The antibody reacts as if it were anti-Co ab ,

IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 55 K.M. B YRNE AND P.C. B YRNE an apparently inseparable specificity. It has been LW . This results in a truncated glycoprotein without shown to be clinically significant in transfusion and it transmembrane and cytoplasmic domains. 4 can cause HDN. 5 LW a and LW ab have very high frequency in all populations tested (albeit, mostly Europeans). The LW b antigen is found in less than 1 percent of most LW Blood Group System The LW (Landsteiner-Wiener) blood group system Europeans, but is present in 8 percent of Estonians, 6 (ISBT: LW/016) 6 is probably most notable for its history. percent of Finns, and 4 percent of Poles. As noted In some early experiments, Landsteiner and Wiener above, only two individuals with a persistent LW(a–b–) produced an antibody in rabbits and guinea pigs that phenotype have been described. Persons with the appeared to have the same specificity as human anti-D. Rh null phenotype are also negative for all LW system Experiments by later workers proved that the original antigens, a phenomenon that reiterates the relationship between Rh antigen expression and LW antigen antibody was not anti-D but that it did have the same 4,5 specificity as that seen in two D+ people. These expression on RBCs (more details follow). antibodies could be adsorbed to exhaustion using D– The LW system antigens are resistant to treatment cells and were therefore not anti-D. For a time, this with ficin/papain, trypsin, and chloroquine. They may be weakened by α-chymotrypsin and are denatured by specificity was known as anti-D-like, but was later 4,5 changed to anti-LW to reduce confusion. 5 DTT (0.2 M). Over the intervening decades, the terminology for LW antigen expression may be transiently this series of antigens has evolved through several depressed during pregnancy and in a variety of disease formats in an attempt to rationalize the observed states, including Hodgkins disease, lymphoma, leuke- serologic reactions and postulated phenotypes: the mia, and sarcoma. The development of autoantibodies following antigen suppression is not uncommon. original terminology attempted to convey the a ab phenotypic relationships that were noted with the D Examples of autoanti-LW and autoanti-LW have been antigen. Thus the current ISBT terminology starts with documented, a scenario which has been known to LW5, since the now obsolete early ISBT numbers had confound serologists. In these situations, it may be been assigned to what are more properly called LW difficult to serologically differentiate between alloanti- phenotypes. 5,6 bodies and autoantibodies in this system without a There are three antigens currently assigned to the series of chronologically distinct specimens, i.e., LW system: LW a, LW ab , and LW b (Table 8). 6 They are predisease, during disease, and postdisease. Antigen suppression may be so drastic that the antigens are carried on a single-pass glycoprotein called LW 4,5 glycoprotein (ICAM-4), the biological function of serologically undetectable. which is as an intracellular adhesion molecule. The As alluded to earlier, expression of LW antigens is glycoprotein is encoded by the LW gene, which is greatly influenced by the presence or absence of Rh located on chromosome 19 at position 13.3. 4 protein. In particular, the strength of expression of LW LW a and LW b are antithetical, the result of a single antigens is directly related to the presence or absence nucleotide substitution on the LW gene (308A>G) that of D antigen. Adults with D+ RBCs have a stronger produces an amino acid change on the LW expression of LW antigens than those with D– RBCs. glycoprotein (Gln70Arg). The molecular basis for LW ab Expression is also influenced by the relative strength of antigen expression has not yet been determined. The D antigen present, i.e., persons with Rh haplotypes that have the highest expression of D antigen, e.g., molecular basis of the only known genetic R2R2, LW(a–b–ab–) phenotype, found in one antenatal have the strongest expression of LW antigens. This patient and her brother, is a 10-bp deletion in exon 1 of phenomenon can lead to misidentification of anti-D, anti-LW a, and LW ab . When an antibody identification panel is tested and all D+ Table 8. LW (Landsteiner-Wiener) blood group antigens samples are moderately or weakly First Incidence (%) 5 ISBT Conventional Historical reported 4 (Caucasians) Notes 4,5 reactive, the conclusion that anti-D is LW5 LW a LW, Rh25 1961 > 99 present is perfectly logical, until the ab LW6 LW LW 1, LW 2, LW 3 1982 > 99 worker notes that the patient is D+. LW7 LW b Ne a 1981 < 1 8% in Estonians; This may be the correct inter- 6% in Finns; pretation, if the patient has a D– 4% in Poles

56 IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 Review: less well-known blood group systems phenotype, or if the patient can be shown to have a has only been described in one individual, who had an partial D phenotype. However, it is also possible that unusual presentation of congenital dyserythropoietic the reactivity pattern seen is due to a relatively weak anemia (CDA) that produced RBCs that were deficient anti-LW that is reactive with those cells with stronger in CD44. Interestingly, the patient also typed Co(a–b–) expression of LW, i.e., those that are D+. 5 Anti-LW can and had a weak expression of LW antigens. 5 be distinguished from anti-D by testing with DTT- The Indian system antigens are sensitive to treated RBCs. Testing with RBCs from a cord sample treatment with ficin/papain, trypsin, α-chymotrypsin, can also aid in identification because on cord RBCs LW and DTT (0.2 M), but are resistant to chloroquine. 4,5 is strongly expressed on both D– and D+ phenotypes. The susceptibility of the antigens to ficin/papain is Antibodies to LW system antigens are usually IgG perhaps one of the most useful tools in differentiating and reactive preferentially by antiglobulin techniques. anti-In b from many of the other antibodies to high- The antibodies are usually produced in response to frequency antigens. exposure to RBCs, but have been found in persons with This apparently simple blood group system is no apparent exposure. They do not bind complement complicated by its relationships to the high-frequency and do not cause in vitro hemolysis. LW system antigen AnWj and the In(Lu) gene. There is convincing antibodies appear to have little or no clinical signi- evidence to indicate that the AnWj antigen is carried ficance, although data are scarce. While these anti- on CD44 and it may eventually be added to the Indian bodies have been reported to cause a positive DAT in blood group system. Expression of AnWj can vary in newborns, clinical HDN has not been reported. strength between individuals. Unlike In a and In b, AnWj Clinicians who must“transfuse against” examples of LW is not affected by treatment with ficin/papain, trypsin, system antibodies will often select Rh negative (D–) or α-chymotrypsin, and is therefore presumably on an units for transfusion, since these RBCs have the weakest area of CD44 that is not cleaved by those enzymes. expression of LW antigens. To date, this practice has Antibodies to AnWj are usually IgG, and are reactive by always resulted in a satisfactory transfusion outcome. 4,5 antiglobulin techniques. Only two examples of alloanti-AnWj have been reported. Others appear to be autoantibodies, with concurrent weakening of RBC Indian Blood Group System The Indian blood group system (ISBT: IN/023) antigens as a consequence of reduced expression of consists of two antithetical antigens: In a and In b.6 The CD44 in a variety of disease states. Examples of anti- AnWj have been shown to cause transfusion reactions. antigens are carried by CD44, a single-pass membrane 4,5 glycoprotein that is encoded by the CD44 gene on Anti-AnWj has not been implicated in HDN. This is chromosome 11 at position p13. The biological not surprising because the RBCs of newborns do not function of CD44 is as a leukocyte homing receptor express AnWj. The switch from AnWj– to AnWj+ and cellular adhesion molecule. The protein is occurs early in life, between days 3 and 46 after birth. widespread and found in a large variety of tissues. 4 Persons who inherit the In(Lu) gene (the The In a and In b polymorphisms arise from a dominant inhibitor of Lutheran system antigens) nucleotide substitution in the CD44 gene (252C>G) exhibit a broad weakening or suppression of Lutheran that results in an amino acid change on the CD44 and related RBC antigens. CD44 on RBCs is suppressed 4,5 in the presence of In(Lu), although expression in other glycoprotein (Pro46Arg). As seen in Table 9, the low- b a tissues is normal. These RBCs express very little In or frequency In antigen is extremely rare in Europeans, a but it has a low prevalence in Indians and is found most AnWj antigen (or In , if present). Sometimes the 5 antigens are only detectable in adsorption/elution commonly in Iranians and Arabs. Persons with the 4,5 In(a+b–) phenotype have only been found in these studies. ethnic groups. The extremely rare In(a–b–) phenotype The Indian system antigens are good immunogens and many examples of the antibodies

Indian blood group antigens have been reported. Most are IgG, Table 9. reacting preferentially by antiglobulin First Incidence (%) 5 ISBT Conventional Historical reported 5 (Caucasians) Notes 5 techniques, although some saline- IN1 In a 1973 < 0.1 4% in Indians; reactive examples have also been 11% in Iranians; reported (possibly indicating the 12% in Arabs presence of IgM antibodies). The IN2 In b Salis 1975 > 99.9

IMMUNOHEMATOLOGY, VOLUME 20, NUMBER 1, 2004 57 K.M. B YRNE AND P.C. B YRNE antibodies do not bind complement and do not cause 3. Daniels GL (Chair), Anstee DJ, Cartron JP, et al. in vitro hemolysis. Anti-In a has not been reported to International Society of working cause transfusion reactions, although data are scarce, party on terminology for red cell surface antigens. probably because In(a+) donors are scarce in most Vox Sang 2001;80:193-6. populations. However, in vivo survival experiments 4. Reid ME, Lomas-Francis C. The blood group antigen indicate that two examples of the antibody rapidly factsbook. 2nd ed. San Diego, CA: Academic Press, cleared In(a+) RBCs. Anti-In b may cause anything from 2003. no reaction to rapid or delayed hemolytic reactions. 5. Issitt PD, Anstee DJ. Applied blood group serology, Neither specificity has been reported to cause clinical 4th ed. Durham, NC: Montgomery Scientific HDN, although the RBCs of a number of infants born to Publications, 1998. mothers with anti-In b had a positive DAT. On the other 6. Daniels G. Terminology for red cell antigens—1999 hand, the RBCs of some infants were DAT negative and update. Immunohematology 1999;15:95-9. maternal anti-In b was not detectable in the infants’ sera. 7. Daniels G (Chair), Cartron JP, Fletcher A, et al. The lack of significant HDN as a result of these International Society of Blood Transfusion antibodies may be related to the presence of CD44 on Committee on terminology for red cell surface many other tissues, particularly the placenta, which antigens: Vancouver Report. Vox Sang 2003;84:244-7. may have a preemptive absorption effect, thereby 8. Wagner FF, Poole J, Flegel WA. Scianna antigens protecting the fetus. 5 including Rd are expressed by ERMAP. Blood 2003;101:752-7.

References Karen M. Byrne, MT(ASCP)SBB, CQA(ASQ), 1. Reid ME, Storry JR. Low-incidence MNS antigens Department of Transfusion Medicine, National associated with single amino acid changes and Institutes of Health, 10 Center Drive, Room 1C711, their susceptibility to enzyme treatment. Bethesda, MD 20892 and Peter C. Byrne, American Immunohematology 2000;17:76-81. Red Cross, Diagnostic Manufacturing Division, 9319 2. Reid ME. Contribution of MNS to the study of gly- Gaither Road, Gaithersburg, MD 20877. cophorin A and glycophorin B. Immunohematology 1999;15:5-9.

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