The Hypogammaglobulinemias

OWEN M. RENNERT, M.D.

Department of Pediatrics, Oklahoma Children s Memorial Hospital, Department of Biochemistry and Molecular Biology, University of Oklahoma, Oklahoma City, OK 73190

ABSTRACT

The immunoglobulin system initially evolved as a defense system to maintain genetic stability during evolution. Studies in the past two decades have resulted in the elucidation of immunoglobulin structure and the def inition of their chemical composition. Disorders of immunoglobulin pro duction have led to an enhanced understanding of the functional aspects of immunoglobulin chemistry. The recognition of these disorders has en hanced our knowledge of antibody specificity and led to the development of immunochemical techniques such as radioimmunoassay as well as the development of techniques of transplantation and immune reconstitution in man.

Introduction new knowledge have been clinically applied for the control of Rh disease, vac In 1799 Dr. Benjamin Waterhouse,11 a cination and immunization, immunosup Massachusetts physician, received a let pression therapy, transplant therapy and ter from his friend in London containing the use of gamma globulin. Another strik a copy of an article by Dr. E. Jenner enti ing advance has been the development of tled, “Inquiry Into the Causes and Ef immunohistochemistry and radio fects of the Variolae Vacinate, or Cow immunoassay techniques in clinical med Pox”. It was Dr. Waterhouse’s response icine. to this article that opened the era of im Over the past two decades, the exis munology in the new world. He wrote, tence of two major components of man’s “On pursuing this work I was struck with immuno defense mechanisms were es the unspeakable advantages that might tablished. It was the pioneering work of accrue to this, and indeed, to the human Good, Cooper, Glick and Peterson6,8 that race at large, from the discovery of a mild established the embryologie and distemper that would ever after secure phylogenetic origins of these two sys the Constitution from that terrible scurge, tems. The initial observation depended the smallpox.” Advances in knowledge in upon the use of the chick as an experi the area of immunobiology have come mental model to investigate the de from the study of immune deficiency dis velopment of the immune system. It was eases in man, and applications of this demonstrated that removal of a

0091-7370/78/0700-0276 $01.20 © Institute for Clinical Science, Inc. THE HYPOGAMMAGLOBULINEMIAS 2 7 7 lymphatic-like organ at the distal portion modern day lamprey eel has the most of the gastrointestinal tract, the bursa of primitive thymic system consisting of not fabricius, produced failure of develop a single organ but a number of scattered ment of the immune system. Shortly foci of lymphoid cells and a primitive thereafter, it was demonstrated that ex spleen. The fully developed immuno tirpation of the thymus in neonatal rab globulin-producing system emerged 250 bits interfered with antibody production million years ago. Sharks and paddle fish and, more specifically, that in newborn had the first well-defined plasma cells in animals it impaired transplantation im spleen, pericardial tissue and other or munity and the cell mediated immune gans capable of gamma globulin synthe responses. sis. Experimental observations on the de The study of immunodeficiency and its velopment of the humoral and cellular evolutionary development emphasizes immune systems indicated the existence the fundamental importance of this sys of crucial periods during embryogenesis tem and suggests that it was the monitor of two organs, the thymus and the bursa ing system to maintain somatic variation of fabricius (or its mammalian equivalent) and yet have the persistence of geneti which determined the proper develop cally stable species. In an evolutionary ment of immunologic mechanisms. The sense, it represents a system that was es thymus represented the site of differ sential in the face of continuous somatic entiation of a population of lymphocytes variation; it could distinguish self from that subserved particularly the functions non-self cells and destroy the latter. of cell mediated immunity, the T-cells. Teleologically, this immune system first This system was fundamental in delayed developed to defend against inside rather allergic reactions, in allograft reactions than outside antigens, so that it could and in initiation of graft vs. host reactions eliminate the unwanted insiders that These cells functioned as a defense sys threatened the integrity of the individual tem against bacteria such as certain gram and the survival of the species.8 negative coliform organisms, salmonella, typical and atypical acid fast bacteria, lis Structural Characteristics of the teria and brucella, fungi and certain Immunoglobulins viruses including chicken pox, measles, vaccinia and others. The prime event in the recognition that The system, identified in the chicken, antibody activity was associated with the was the bursa of fabricius. This system gamma globulin fraction of plasma pro and its homologous counterpart in mam teins was made by Tiselius and Kabat12 in mals activates the humoral antibody 1938. In 1950, the identification of mechanisms once recognition has been heterogeneity in the gamma globulin affected. Histologically, it consists of the fraction, the existence of sub-classes, morphologically larger lymphocytes of namely, IgG, IgM, IgA, IgD and IgE, the germinal centers and plasma cells was established. The basic structural and their functional products the 7-globulin plan of these glycoproteins immunoglobulins. consists of four polypeptide chains which The evolutionary development of the are symmetrical about the long axis of the thymus dependent system may be traced molecule. Two of the four polypeptide to the evolution of early vertebrate forms chains are common to all immuno and appeared 400 million years ago globulins. The structural relationships of amongst primitive marine vertebrates these polypeptide chains using enzyma and perhaps some invertebrates. The tic cleavage was carried out by Porter in 2 7 8 RENNERT

1959. Proteolysis with the enzyme papain molecules do not. The anti-Rh antibody identified three fragments. Two were the is associated with classes IgG 1 and 3. Fab fragments, the antigen binding ends The anti-A antibody is associated with of the immunoglobulin molecule with a IgG 1, and the anti-factor 8 antibody is molecular weight of approximately associated with IgG 4. 52,000 dal tons. The third fragment, the The major secretory antibody is IgA. It Fc fragment, was crystallizable and had a constitutes approximately 15 percent of molecular weight of approximately the antibody activity of serum. It exists as 48,000. The intact globulin molecule has monomer and dimer forms with sedimen a molecular weight of 150,000 dal tons. tation coefficients from 7S to 5S. Exactly Structural investigations employing 6.4 percent of this glycoprotein is carbo mercaptoethanol and urea treatment, gel hydrate, and it is linked by an filtration identified the existence of two N-glycoside bond to asparagine. The major chains: the H (heavy) chain with a mean salivary IgA concentration is 28 mg molecular weight of 53,000 and the light per 100 ml, in tears it is 7 mg per 100 ml chain, the L-chain having a molecular and in colostrum it is 150 mg per 100 ml. weight of 22,000 daltons (consisting of Most secretory IgA is in the 11S globulin either kappa or lambda units). These class. This antibody group does not fix chains were joined to one another by di complement, neutralizes viruses and is sulfide bonds with H chains being at incapable of crossing the transplacental tached to the L chains at the carboxy ter barrier. minus by a disulfide bond and the H The macroglobulin gamma globulin chains being held together by a variable fraction is IgM. It has a sedimentation number of disulfide bonds. The struc co-efficient of 19 S with a molecular tural chemistry and sequence of much of weight of approximately 900,000 daltons. the immunoglobulin system is such that It consists of five subunits with 10 com antigens are bound to the Fab fragment bining sites for antigens. Approximately in a region that constitutes no more than 5 10 percent of this glycoprotein is car percent of the gamma globulin chain. bohydrate and it is attached to the n The precise amino acids sequence of this chain. It contains two major classes of an region is still not known. tibodies, one against lipopolysaccharide The IgG fraction constitutes 75 to 85 antigens such as the Wasserman and percent of the serum antibodies in man. Forseman blood group antigens, and the Its antibody activity is predominantly di other to a variety of endotoxins. This rected against pyogenic bacteria, viruses antibody class is synthesized by the fetus and antitoxins. Two to eight percent of from the 20th gestational week on and is this glycoprotein is carbohydrate with the the major antibody class by which the carbohydrate being bound to the protein fetus responds to intrauterine infection. core by asparagine at amino acid position Adult levels of this serum immuno 297 from the N terminal end. The anti globulin are achieved by the sixth post body class crosses the placenta by an ac natal month. tive transport mechanism which appears The newest class of antibodies is made to involve recognition of the FC frag up of IgD and IgE. IgE is the serum ment. Four classes of IgG antibodies reaginic antibody found in individuals have been recognized, IgG 1, 2, 3 and 4. who are ragweed sensitive. It is the anti IgG 1, 2 and 3 have the capacity to fix body responsible for the classic complement, whereas the class 4 does Prausnitz-Kiistmer test, fixes to human not. Classes 1, 3 and 4 are capable of fix and monkey skin, is heat labile and is ing to skin receptors, whereas class 2 IgG neutralized by allergins. The interaction THE HYPOGAMMAGLOBULINEMIAS 2 7 9

of IgE with antigen is mediated by his coccus and hemophilus. These infections tamine release. There are two classes of respond to antibiotic therapy; however, in IgE and they contain 10 percent to 11 spite of chemotherapy the patients suc percent carbohydrate. IgD is the serum cumb to pulmonary complications of infec antibody identified in myeloma patients tion. No increased susceptibility to virus (more than 20 patients) with no known infections nor to infections by enterococci antibody activity. or gram-negative bacilli are observed. In Genetically determined variations in the recent years, the increased association the primary structure of gamma globulins of autoimmune disease has been recog have been identified in humans and nized in these patients. One-third to these mutational changes occur in the one-half of them exhibit symptoms of kappa L chain and in the gamma H chain rheumatoid arthritis and/or a dermato- in IgG 1, 2 and 3. The amino acid se myositis-like syndrome. Additionally, quence differences, owing to recognized these children may have a degenerative alleles and the extensive homologies in central nervous system disease with sequence between the constant portions lymphocytic infiltration in the cerebrum. of various immunoglobulins, suggest that An increased frequency of hemolytic the complex immunoglobulin system has anemia, eczema, asthma and drug erup arisen from gene duplications of a single tions also plague .these patients. primordial cistron. The diagnosis is established by the presence of IgG concentration less than Disorders of the Immunoglobulin System 100 mg per 100 m l.1 IgA and IgM serum levels are less than 1 percent of the normal In 1952, Bruton2 described an eight value. Further evidence of a deficient year old boy who presented with septic humoral immune system is the presence of arthritis and absence of gamma globulins abnormally low levels of isohemag on protein electrophoresis. Bruton iden glutinins and a positive Shick test. The tified an increased frequency of infec diagnosis is further confirmed by the dem tions in this patient, including 19 onstration of normal delayed hyper episodes of pneumococcal sepsis as well sensitivity to antigens such as tuber as repeated upper and lower respiratory culosis, Candida or dinitrochlorobenzene. infections. This was the first documented Histologic examination of lymph nodes association of the enhanced infection rate reveals absence of plasma cells (figure 1) and inability to produce gamma globu and normal thymic structure and architec lins. This disease is inherited in a sex- ture. Clinically, the deficiency of lympha linked fashion. At present, a variety of de tic tissue manifests itself in the absence of fects in the synthesis of individual classes tonsils on physical examination. Treat of gamma globulins, as well as in the cel ment consists largely of gamma globulin lular immune system, have provided the replacement therapy. basis for a definition of the genetic con Agammaglobulinemia may occur as an trol of this system. acquired entity (primary acquired Patients with this sex-linked form of a agammaglobulinemia). It is a clinical con gammaglobulinemia are disease-free the dition characterized by sudden depression first six to nine months of postnatal life, a of gamma globulin synthesis and occurs consequence of the transplacental passage with equal frequency in males and of maternal IgG. Subsequently, they ex females.3 Specific etiologies of the hibit increased susceptibility to infection, agammaglobulinemia have not been principally to pyogenic organisms such as documented. There are reports of multiple staphylococcus, pneumococcus, strepto cases in single kindred; however, a genetic 2 8 0 RENNERT

F i g u r e 1. Histology of lympli node and spleen showing absence of plasma cells and ab sence of well formed follicles. A: Aortic node; B: Spleen, (x 100).

basis of this disease has not been clearly granulomas. The pathophysiology ofthese established. In this entity, as in the sex- granulomas is unclear and they do not re linked variety, there is a high incidence of spond to adjunctive steroid therapy. autoimmune disease such as lupus, The laboratory diagnosis is established hemolytic anemia and thrombocytopenic by the demonstration of serum IgG levels purpura. Associated prominent clinical of < 500 mg per 100 ml and the presence of features are malabsorptive disease normal serum levels of IgA and IgM.9 His characterized by steatorrhea and protein- tologic examination of lymph nodes re losing enteropathy. No pathogenetic veals an abiotrophy of follicles or follicular mechanism has been presented to explain hyperplasia with the absence of plasma the gastrointestinal disease; however, pa cells. Short-term culture studies include tients show clinical improvement follow the demonstration of decreased desoxy ing treatment with either gluten or milk ribonucleic acid (DNA) and ribonucleic free diets. A frequently observed compli acid (RNA) synthesis in phytohemagglu cation is the occurrence of noncaseating tinin treated lymphocytes. THE HYPOGAMMAGLOBULINEMIAS 2 8 1

Dysgammaglobulinemias Louis Bar Syndrome10 of ataxia, telan giectasia, increased chromosomal breaks These clinical entities are divided into and increased incidence of neoplasms. two major groups.5 The first group is Additionally, IgA deficiency has been as characterized by the absence of serum sociated with deletions of the long arm of IgA and IgG with normal or increased chromosome 18; however, this has not levels of IgM. The IgM levels in patients been a constant finding. are & 150 to 1,000 mg per 100 ml (re cently several patients have been Combined Immunodeficiency documented with increased levels of There are two primary forms of com IgD). This diagnostic grouping is hetero bined immunodeficiency.7 One is au geneous, primary (genetic) forms with tosomal recessive and the other is sex- two modes of inheritance (sex-linked re linked in its inheritance pattern. Patients cessive and autosomal recessive) ac display evidence of recurrent infections quired forms whose etiology is unclear. at three to six months of age and then Clinically, these patients have increased gradually succumb to progressively de susceptibility to infection, thrombocyto bilitating infections by two years of age. penia and neutropenia. Symptoms are chronic diarrhea, sec Additionally, they show characteristic ondary salmonella and enteropathic E. renal lesions and an autoimmune anemia. coli gastroenteritis. Pulmonary infections Pathological examination of the lympho- with pseudomonas and/or pneumocys- reticular system demonstrates well- tis carinii are major complicating factors. defined follicles with plasma cells which These children have increased cutaneous give a positive PAS reaction and a Candida infections, progressive failure to fluorescence when stained with thrive and ultimate death. The initial de fluoroscein-antibody to IgM. The pos scription in 1950 and subsequent studies itive PAS reaction is secondary to the indicated the functional absence of anti high content of carbohydrate of IgM and body synthesis in these patients. A rela identifies the increased macroglobulin tively severe leukopenia with less than accumulation. Patients with dysgamma- 2,000 leukocytes per mm3 is also found. globulinemia are treated with immuno The circulating leukocytes are made up globulins resulting in correction of the of lymphoblastic elements and an in thrombocytopenia and suppression of the creased number of eosinophils. elevated IgM levels. Bone marrow histology reveals de The second type of dysgammaglob- creased plasma cells and increased num ulinemia is characterized by the absence bers of lymphoblasts and lymphocytes. of serum IgA and secretory IgA with as These patients have a deficiency of the sociated normal levels of IgG and IgM. It humoral immune system and also an ab must be recognized that a small percen normality of the T-cell system as evi tage of the normal population may exhibit denced by the absence of delayed sensi absent or abnormally low levels of serum tivity reactions (monilia skin test and IgA and a diagnostic requisite is the dinitrofluorobenzene). In vitro studies of demonstration of the absent secretory peripheral lymphocytes in culture systems IgA. This syndrome is characterized by a identify unresponsiveness to mitogenic sprue-like syndrome and decreased agents. The thymus is atrophic showing production of IgA in cells of the lamina the absence of Hassells corpuscles and propria of the intestinal tract. Several dysplasia-abnormalities probably sec conditions have been associated with ab ondary to the failure of descent of the me sence of IgA. Most notable of these is the diastinal structures. 2 8 2 RENNERT

Major advances in our understanding of 2. Bruton, O.: Agammaglobulinemia. Pediatrics the immune system have come from the 9:722-726, 1952. 3. Ch a ra ch e, P., Rosen, F., Jan ew a y , C., Cr a ig , study of immunodeficient disorders in J., and Rosen berg, H.: Acquired agammaglob man. In the past few years, the identifica ulinemia in siblings. Lancet 1:234-236, 1965. 4. Copper , M., Peterson, R., and Go o d , R.: De tion of chemical abnormalities in the me lineation of the thymic and bursal lymphoid tabolism of purines have identified systems in the chicken. Nature 205:143-145, specific biochemical abnormalities as 1965. 5. G l e ic h , G., Uh r , J., and Vaughan ,J.: Antibody sociated with combined immunodefi formation in dysgammaglobulinemia. J. Clin. ciency diseases and disorders of T-cell Invest. 45:1334-1339, 1966. and macrophage function. With this ad 6. G lic k , B., Ch a n g , T., and Jaap, R.: The bursa of fabricius and antibody production. Poult. Sci. vance in our understanding of the basic 35:224-231, 1956. immunobiology, the recent pastyears have 7. G o o d , R.: Immunologic reconstitution: the heralded the application oftransplantation achievement and its meaning. Immunobiology. Good, R. and Fisher D., eds. Hartford, Sinauer therapy for the immunologic reconstitu Press, 1971, pp. 231-239. tion of such patients. These efforts have 8. G o o d , R. and Papermaster, B.: Autogeny and been technically successful and have phylogeny of immunoglobulin immunity. Ad further enhanced our understanding of the vances Immunol. 4:1-34, 1964. 9. H o n g , R. and Go o d , R.: Limited heterogeneity defense system present since early evolu of gamma globulin in hypogammaglobulinemia. tion of man. Science 756:1102-1105, 1967. 10. M c Fa r l in , D., St rober, W., and W aldm a nn, T.: Ataxia telangiectasia. Medicine 51:281-287, 1972. References 11. Rapport, S. and W rig h t , H.: Great adventures in medicine. New York, Dial Press, 1952, pp. 1. Baco n , S. et a l : Antibody production by hypo 170-172. gammaglobulinémie patients. J. Immunol. 12. Tiseliu s, A. and Kabat, E.: Electrophoresis of 88:443-447, 1962. immune serum. Science 87:416-419, 1938.