1012 J Clin Pathol 1991;44:1012-1017 Tissue distribution of human y$ T cells: No

evidence for general epithelial tropism J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from

T M Vroom, G Scholte, F Ossendorp, J Borst

Abstract peripheral lymphoid organs."6 More than In man and mice only a small proportion 90% of T cells in the murine epidermis, of T cells in the peripheral lymphoid however, express TCR y6,78 while y6 T cells compartment express the y8T cell recep- have also been reported to constitute a very tor (TCR). In mice, however, yB T cells large proportion of T cells in the epithelia of comprise the predominant population at reproductive organs,9 tongue,9 and intestine.'" particular epithelial sites-in epidermis Strikingly, certain Vy and V6 gene segments and epithelia of intestine, reproductive are expressed predominantly in different organs, and tongue. The distribution of murine tissues. Moreover, the diversity within y5 T cells in normal human tissues was the y6 population differs greatly, depen- investigated, paying particular attention ding on the tissue. The epidermal y6 T cells to epithelial layers. In all lymphatic express V5/J1/Cy1 and VI/D2/J2/CQ encoded organs and in epithelia of a wide variety receptor chains" and can be considered clonal, of non-lymphatic organs, including the likewise the y3 T cell population in repro- respiratory tract, male and female re- ductive organs and tongue that expresses productive organs and tongue, y5 T cells V6/J1/Cy1 and V1/D2/J2/C6 encoded recep- constituted less than 5% of total T cells, tor chains.912 In intestinal epithelium" '3 and with the remainder expressing TCR 4p. in peripheral lymphoid organs'4 a large TCR The only exception was the intestine, yc repertoire exists that mainly depends on where yJ T cells were preferentially junctional diversity, while Vy7 and Vy4 gene situated in the columnar epithelium of segments are used preferentially at these re- the crypts, rather than in the lamina spective sites. Due to their specific localisation propria. in certain murine epithelia, their limited It is concluded, therefore, that human receptor diversity at two of these sites, and y5 T cells do not display a general epi- their potential specificity for the evolutionary thelial tropism and are, in terms of conserved heat shock proteins,"5 it has been relative numbers, no more able than a4 postulated that y6 T cells may have a special- T cells to out ised role in the carry continuous surveil- continuous immunosurveil- http://jcp.bmj.com/ lance of the immune system against in- lance of epithelia.""'8 fection or transformation in epithelia. yv In man TCR y6 bearing cells constitute less T cells may, however, have a specialised than 2% of CD3 positive thymocytes and less function in the epithelium of the intes- than 1-20% of peripheral blood T cells'920 In tinal tract. lymphoid organs y6 T cells constitute less than 5% of the T lymphocytes.202' With res-

pect to the epithelial localisation of human y6 on October 1, 2021 by guest. Protected copyright. Two types of T cell antigen receptors (TCRs) T cells one clear difference with the murine are now known, the a, and the yb system is already apparent: in human skin y6 Department of heterodimer, which are expressed at the cell T cells are not the predominant T cell popula- Pathology, Rotterdam surface in association with the CD3 molecular tion, nor in epidermis nor dermis.2022 In intes- Cancer Center, complex.'` Each TCR chain contains a vari- tine the situation seems more comparable be- Rotterdam, The able and a constant domain, encoded by dif- tween man and mice, with human yc T cells T M Vroom ferent gene segments V, (D), J and C that localising preferentially in the epithelium Department of combine by rearrangement during T cell dif- rather than in the lamina propria.2'2' Pathology, Slotervaart ferentiation. Although the y and loci We have quantitated y6 and ac, T cells in a Hospital, Amsterdam together contain fewer different of T M Vroom gene segments great variety normal human lymphatic and G Scholte than the a and loci, the potential repertoire non-lymphatic tissues, including the res- Division of of TCR yb is very large as one gene can piratory system, the male and female uro- , The incorporate more than one D segment,4 genital tract, and the tongue, which had not Netherlands Cancer which, with the addition of nucleotides at the previously been investigated. Special atten- Institute, Amsterdam F Ossendorp junctions, gives rise to a great variety of tion was paid to the various epithelial layers J Borst sequences.' At present, it is not clear what within these tissues to shed light on the pos- Correspondence to: contribution yb T lymphocytes make to the sible function of human yv T cells in epithelial Jannie Borst, Division of immune system. They may complement T surveillance. Immunology, The a# Netherlands Cancer cells in terms of antigenic specificities, func- Institute, Plesmnanan 121, tional capabilities, or sites of action within the 1066 CX Amsterdam, The Netherlands. body. Methods Accepted for publication In mice, yb T cells form a minority of the Normal tissues were obtained from necropsies 12 June 1991 total T cell population in the thymus and or from normal parts of surgical specimens. Tissue distribution ofhuman yv T cells 1013

Samples were derived from adults, unless was stained with haematoxylin and eosin for otherwise indicated. For every type of tissue histological examination. at least two samples from different subjects Monoclonal used for staining tis- were investigated. The following tissues were sues were: Identi-T #F1 (anti-TCR a)27 from J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from examined: (1) lymphatic and haemopoietic T cell Sciences, Cambridge, Massachusetts, organs (a) thymus, fetal (12 weeks pregnancy) used at 2 Mg/ml; anti-TCR yb-l (hybridoma and neonatal, (b) lymph node, neonatal and name 1 F2, anti-TCR yb),'9 used at 2-4 adult, (c) tonsil, infantile, (d) spleen, (e) bone Mg/ml; CLB-T3 (anti-CD3) from Dr R van marrow, (f) liver, fetal (12 weeks pregnancy), Lier, Central Laboratory of the Red Cross neonatal and adult; (2) skin, fetal and adult; Blood Transfusion Service, Amsterdam, The (3) digestive tract (a) tongue, (b) salivary Netherlands, used at 5 pg/ml. Staining with glands, (c) oesophagus, (d) stomach, (e) small anti-TCR monoclonal antibodies was done intestine, (f) large intestine, (g) appendix; (4) according to the alkaline phosphatase-anti- urogenital tract (a) kidney, (b) ureter, (c) alkaline phosphatase method, with other urethra, (d) vagina, (e) uterus and cervix, (f) monoclonal antibodies according to the alka- testis and epididymis; (5) respiratory tract (a) line phosphatase method. Anti-TCR mono- nasal cavity, (b) trachea, (c) lung. clonal antibodies were tested for reactivity on Small tissue blocks were snap-frozen and cytocentrifuge preparations of TCR a,B stored in liquid nitrogen. Sections (8 gm positive and TCR yb positive T cell clones.'9 thick) were cut on a Reichert-Jung 2800 Frigocut Cryostat (Reichert-Jung GmbH, Nussloch, Germany), air dried, and fixed in acetone for 10 minutes. Fixation and all sub- Results sequent washes and incubations were perfor- To determine the proportion ofT lymphocytes med at room temperature. After fixation, sec- that expressed either TCR axf or TCR yb, serial tions were washed three times in phosphate sections were stained with anti-TCR 4a#, anti- buffered saline (PBS), pH 7-2. For the im- CD3, and anti-TCR yb monoclonal antibodies, munoalkaline phosphatase detection method in this order. Only tissue sections that showed sections were incubated with monoclonal no evidence ofinflammation were included, but , diluted in PBS with 1% bovine intestine, lung, and endometrium and vagina serum albumin (BSA) (PBS/BSA), washed always show more or less reactive lesions. three times in PBS and incubated with alka- line phosphatase conjugated rabbit anti- LYMPHATIC AND HAEMOPOIETIC ORGANS mouse immunoglobulin (RaMIg-AP, Dako- In neonatal and fetal thymus less than 5% of patts D314, Glostrup, Denmark), diluted 1 in CD3 positive cells expressed TCR y6. In 20 in PBS with 10% normal human serum. accordance with published data,20 yb T cells For the alkaline -phosphatase-anti-alkaline were found preferentially in the juxta- phosphatase detection method, sections were medullary region of the cortex and in the first incubated with undiluted normal rabbit medulla and rarely present in the outer cortex.

serum, followed by incubation with mono- No preferential association of yb T cells with http://jcp.bmj.com/ clonal antibody and then unconjugated rabbit Hassall's corpuscles was found. anti-mouse immunoglobulin (Dako Z259), In lymph nodes, tonsil, and Peyer's patches diluted 1 in 25 in PBS/BSA with 10% normal less than 5% of CD3 positive cells expressed human serum, as second step reagent, fol- TCR yb. In contrast to a,B T cells, yb T cells lowed by washing with PBS and incubation were not found within the lymph follicles. Of with alkaline phosphatase-anti-alkaline phos- the numerous T cells present within the lym-

phatase complex (Dako D65 1), diluted 1 in 40 pho-epithelial area of the tonsillar crypts, less on October 1, 2021 by guest. Protected copyright. in PBS/BSA. Subsequently, sections were than 5% expressed TCR yb. washed three times in TRIS-buffered saline, In spleen yb T cells were again less than 5% pH 7-6, and incubated with staining solution of total CD3 positive cells in the periarteriolar for 30 minutes in the dark. This solution was lymphoid sheath outside the lymph follicles made according to the method of Li et al,26 and in the sinusoids of the red pulp. We could with modifications. It contained 0-5% v/v of not confirm the finding of others2 25 that yb T a freshly prepared 1:1 mixture of 4% w/v cells are relatively more abundant in the red New Fuchsin (Chroma 1B467, Stuttgart, pulp than in the periarteriolar sheaths. Germany) in 2 M HC1 and 4% w/v NaNO2 in In normal bone marrow and fetal (12 week H2O, 3% v/v of a solution of 1% w/v Naphtol pregnancy), neonatal, and adult liver yb T cells AS-MX phosphate (N-5000, Sigma Chemical constituted less than 5% of total CD3 positive Co, St Louis, Missouri) in dimethylfor- cells. mamide and 0-025% w/v Levamisole (Sigma L-9756). The staining solution was made in EPITHELIAL TISSUES 0 2 M TRIS-HCl, pH 8-0, and filtered before Skin use. After staining, sections were rinsed with In agreement with published data20 22 y5 T cells distilled water, counterstained with Mayer's were extremely rare in skin sections (less than haematoxylin, washed in running tap water 1% of CD3 positive cells) derived from adults, and mounted in glycerin-gelatin. Negative as well as in one fetal specimen (12 week control sections were processed as described pregnancy). When observed, they were local- with omission of the incubation step with ised in the basal layer of the epidermis or, in monoclonal antibody. Apart from immuno- higher numbers, perivascularly in the papillary histochemistry, one section of each sample dermis. 1014 Vroom, Scholte, Ossendorp, Borst

Figure I Section of Digestive tract human vagina showing one We paid attention to the tongue, salivary of the very rare TCR yv positive cells (arrow) near glands, oesophagus, stomach, small and large the basement membrane intestine and appendix. Sections from one J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from (immunoalkaline tongue sample showed some CD3 positive cells phosphatase-anti-alkaline within the squamous epithelium and in the phosphatase staining). subepithelial layer. None of these T cells expressed TCR yb. Non-inflamed salivary glands (six specimens) did not contain any T lymphocytes within the epithelium ofthe ducts and acini. Within the surrounding collagenous stroma, scattered CD3 positive lymphocytes were observed, of which none expressed TCR yb. In the squamous epithelium of the oeso- phagus near the basement membrane, occas- ional yb T cells were found, which constituted less than 5% of CD3 positive cells at this site. Figure 2 shows one such intraepithelial yb T cell. In inflamed oesophagus most CD3 positive cells also expressed TCR cx, (more than 95%). In the stomach (three specimens) af T cells Urogenital tract were detected in the lamina propria, while in In the urogenital tract we looked at ureter, the crypt epithelium a,B T cells and yb T cells urethra, kidney, uterus, cervix, vagina, ovary, could not be positively identified, because of testis and epididymis. In normal renal sections the overwhelming endogenous alkaline phos- (eight specimens) no yb T cells were found. phatase activity of the epithelial cells. This This was not surprising as CD3 positive cells activity could not sufficiently be inhibited by were also only rarely observed. The same holds Levamisole. true for the ureter and the urethra (two Serial sections were prepared from human specimens each), testis and epididymis (two small and large intestine at different sites specimens each). Tissue sections of uterus, (duodenum, jejunum, ileum, sigmoid, cecum, cervix, and vagina were derived from patients appendix), using tissue samples from six that had undergone hysterectomy because of adults. The results can be summarised as the presence of myomata. Therefore, these follows: quantitated as total cells per relevant samples contained reactive lesions. The surface area, afi T cells were localised endometrial layer, including columnar epithe- predominantly in the lamina propria, rather lium and lamina propria (two specimens), and than in the columnar epithelium of the intes- the stratified squamous epithelial layers of tinal crypts, while yb T cells were localised in cervix and vagina (five and two specimens the epithelium, rather than in the lamina

respectively) included normal regions that con- propria (figs 3A-C). Despite the preferential http://jcp.bmj.com/ tained only very few CD3 positive cells, of localisation of y' T cells within the intestinal which none expressed TCR yb. In slightly epithelium the absolute number of ac T cells inflamed regions the number of CD3 positive was such that they outnumbered yb T cells, not cells was increased, both in epithelium and in only in the lamina propria (more than 95% of lamina propria. In these cases, yb T cells also CD3 positive cells), but also in the epithelium constituted less than 5% oftotal T cells. When (70-90%0 of CD3 positive cells). The relative present in the squamous epithelium sections number of yb T cells within the epithelium on October 1, 2021 by guest. Protected copyright. they were found in the basal layer (fig 1). varied greatly, not only between different sites in the intestinal tract, but also between sections of the same site originating from different subjects. As in the reproductive tract, inflam- matory activity may significantly influence the Figure 2 Section of human oesophagus showing distribution of these two T cell subsets within one TCR yb positive cell the intestine. near the basement membrane (immuno- alkaline phosphatase-anti- Respiratory tract alkaline phosphatase Lung and trachea were difficult to investigate, staining). because all specimens (more than four) showed a more or less inflammatory activity. It was clear w. .... that, inflamed or not, only a small proportion of CD3 positive cells found in the epithelial layer and in the lamina propria were TCR yb positive (less than 5%) (fig 4). In one specimen, however, up to 10% ofthe T cells were TCR yb positive. These were localised primarily in the interalveolar septa. Although in the nasal cavity (eight specimens), CD3 positive cells were found, also intraepithelially, yb T cells were observed extremely rarely and then in the lamina propria. Tissue distribution ofhuman y6T cells 1015

Figure 3 Serial sections I' -.4 ofhuman appendix showing TCR yb positive mu, I* cells (A) CD3 positive J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from cells, (B) TCR a4 } positive cells (C) TCR a4 positive cells are abundant S around a lymphfollicle It (thick arrows), andfound * within the lamina propria, f , but relatively less .p ?s' predominant in the z9 .V epithelium, while TCR yb Vr positive cells are S."a predominantly located within the crypt epithelium (arrow heads and thin arrow). Two cells detected t jr in the sections stainedfor TCR yo as well asfor CD3 are indicated by arrow heads (immuno- alkaline phosphatase-anti- alkaline phosphatase staining).

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C 1016 Vroom, Scholte, Ossendorp, Borst

Figure 4 Section of minority of total T cells.2022 The absolute human lung showing one numbers of epidermal T cells per unit of TCR y5 positive cell surface area is also significantly lower than in (arrow) lying in an interalveolar septum mice, while the morphology of the few detec- J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from (immunoalkaline table yb T cells is not comparable with that of phosphatase-anti-alkaline the highly dendritic murine epidermal yb T phosphatase staining). cells.2022 In chickens epidermal CD3 positive cells also very rarely express TCR yb.33 In cattle, yb T cells have been reported to occur in high numbers in the skin,3' but they are localised primarily in the dermis, reflecting most likely the abundance of yb T cells in .:.... circulation.3' Murine yb T cells would also constitute a .,.:. g MMNSR\ major proportion of T cells in epithelia of vm reproductive organs and tongue, according to immunohistology and PCR analysis.912 The ARW .:...... '... intraepithelial y6 T cell subsets in murine skin3' and reproductive organs/tongue35 are both derived from the thymus during ontogeny and Discussion express monomorphic receptors. In the human In the past few years yb T ce] Ils have been female and male reproductive organs and in the identified in man, mice, chickenIs, rats, cattle, tongue, the equivalent of the murine intra- sheep and pigs. While in man, m ice, and rats28 epithelial yb T cell type could not be found. the contribution of yb T cells to the total Although y3 T cells have been reported to circulating T cell population is lIcaw (about 5% occur in the murine lung,36 they constitute only on average), the yb T cell pool in peripheral about 10% of total intraepithelial T cells. The blood is relatively large in chickeris (25-30% of analysis of human lung tissue gave a similar total T cells,29 sheep,30 cattle3' atnd pigs32 (15- result. 50%, depending on the animal arad its age). In our studies the epithelium ofhuman small In the human thymus yb T cellls were found and large intestine (including appendix) con- in the juxta-medullary region oftthe cortex and' tained more yb T cells than any of the other in the medulla, rather than in the outer cortex, epithelia investigated (10-30% oftotal T cells). in agreement with published daita.202' In the In other parts of the gastrointestinal tract the chicken thymus33 yb T cells are .also relatively contribution of yb T cells to the intraepithelial sparse in the cortex, despite their abundance in T cell population was smaller. In accordance the periphery. In sheep two pihenotypically with published results,2325 yb T cells were distinct types of yb T cells can be detected that found preferentially within the epithelium of occur in the cortex and in the medulla, respec- the intestinal crypts, rather than in the lamina tively.0 The developmental rela tion between propria, where significant numbers of 4xB T http://jcp.bmj.com/ these cell types is unclear. Associ;ation with the cells were present. The same differential dis- epithelial cells of Hassall's corpu~scles has been tribution of a4 and yb T cells has been reported reported for bovine3' and ovirae3' TCR yb for the chicken intestine.33 In sheep and cattle positive thymocytes, but not for murine cells. yb T cells occur in lamina propria as well as We have no evidence for such an association in epithelium.3' 32 the human thymus. It remains to 1be established While it cannot be denied that yb T cells in to what extent T cells undergo the same various species show certain preferential

yb on October 1, 2021 by guest. Protected copyright. thymic differentiation and selectic nprocesses as associations with epithelial cells, we conclude a4 T cells. that there is no evidence for general epithelial In lymph node, tonsil, Peyer'"s patches and tropism of yb T cells in man or other species. spleen yb T cells constituted a sm;all proportion Only within the large and small intestine do yb of total T cells and essentially followed the T cells clearly show a preferential intraepithe- distribution of a4 T cells. Strikinjgly, yb T cells lial localisation in all species investigated. The were not found at all within lyImph follicles. combined data suggest that the intestinal epi- This could be a reflection oftheir relatively low thelium harbours a yb T cell population that numbers. They were also not se(en in reactive has at least in part developed extrathy- nodes, with high numbers of iintrafollicular mically.37339 The relativeyecontribution of T CD4 positive a4B T cells. In 4cattle, where cells to the total pool of murine intestinal circulating yb T cells are much mc )re numerous, intraepithelial T cells varies significantly, intrafollicular yb T cells are alrso rarely ob- depending on antigenic stimulation. Exposure served.3' We were not able to sulbstantiate the to antigens leads to an increase of intraepithe- differential distribution of 4,B axid yb T cells lial a4 T cells, while the absolute number of yb reported for humani2"' and chic-ken33 spleen, T cells remains quite constant.38 Most with yb T cells primarily locateci in the sinu- intraepithelialyr T cells constitute a resident soids and a T cells in the periarte-riolar sheath. population that is not directly connected to the It remains to be established wheither yb T cell circulating pool, while a4 T cells can enter the recirculation differs essentially frrom afl T cell epithelium from circulation during infection. trafficking. In man this is also evidenced by a difference in In contrast to the situation in miurine epider- yb T cell repertoire. While in most people the mis, in the human epidermis yb T cells are a V32 gene segment is expressed preferentially Tissue distribution ofhuman yv T cells 1017

on peripheral yb T cells, the intestinal epithe- 13 Takagaki Y, DeCloux A, Bonneville M, Tonegawa S. Diversity ofyo T cell receptors on murine intestinal intra- lium harbours predominantly Vb1 positive yb epithelial lymphocytes. Nature 1989;339:712-4. T cells.24 The same sort of discrepancy in V 14 Jones B, Carding S, Kyes S, Mjolsness S, Janeway CA, Hayday A. Molecular analysis ofTCR y gene expression in gene usage is observed in mice. In cattle two allo-activated spleen cells of adult mice. Eur J Immunol J Clin Pathol: first published as 10.1136/jcp.44.12.1012 on 1 December 1991. Downloaded from types of intestinal intraepithelial yb T cells can 1988;18:1907-15. 15 Haregewoin A, Soman G, Hom RC, Finberg RW. Human be observed, a resident intraepithelial popula- yo' T cells respond to mycobacterial heat-shock protein. tion (T19 negative) and a yb T cell population Nature 1989;340:309-12. 16 Janeway CA, Jones B, Hayday A. Specificity and function of (T19 positive) in the lamina propria that is T cells bearing yo receptors. Immunol Today 1988;9:73-6. most likely derived directly from the large 17 Janeway CA. Frontiers ofthe immune system. Nature 1988; 333:804-6. circulating pool of yb T cells.3' It will be very 18 Raulet DH. Antigens fory/o T cells. Nature 1989;339:342-3. interesting to examine the specific contribution 19 Borst J, Van Dongen JJM, Bolhuis RLH, et al. Distinct molecular forms of human T cell receptor y detected on of this resident intestinal epithelial yb T cell viable T cells by a monoclonal antibody. J Exp Med 1988; population to the immune response. A clue may 167:1625-44. 20 Groh V, Porcelli S, Fabbi M, et al. Human lymphocytes come from the observed expansion of intestinal bearing T cell receptor yo are phenotypically diverse and yb T cells in coeliac disease.25 evenly distributed throughout the lymphoid system. J Exp Med 1989;169:1277-94. In other human epithelia a,B T cells would be 21 Falini B, Flenghi L, Pileri S, et al. Distribution of T cells the population most fit to perform the function bearing different forms ofthe T cell receptor y/b in normal and pathological human tissues. J Immunol 1989;143: of epithelial surveillance, at least as judged by 2480-8. the relative numbers ofcells that could respond 22 Bos JD, Teunissen MBM, Van der Kraan J, et al. T-cell receptor yo bearing cells in normal human skin. J Invest to an infectious agent. Obviously, it remains an Dermatol 1990;94:37-42. intriguing question whether yb T cells would 23 Spencer J, Isaacson PG, Diss TC, MacDonald TT. Expres- sion of disulphide-linked and non-disulphide-linked be more fit to respond to certain antigens forms of the T-cell receptor y/o heterodimer in human because of a more suitable receptor repertoire. intestinal intraepithelial lymphocytes. Eur J Immunol 1989;19: 1335-8. Alternatively, yb T cells may contv-bute in the 24 Bucy RP, Chen C-L, Cooper MD. Tissue localization and immune response by carrying out a specific CD8 accessory molecule expression of Tyo cells in humans. J Immunol 1989;142:3045-9. function. 25 Halstensen TS, Scott H, Brandtzaeg P. Intraepithelial T cells of the TCR y/o+CD8- and Vol/Jol + phenotypes are increased in coeliac disease. Scand J Immunol 1989; 30:665-72. This work was supported in part by Constantijn en Christiaan 26 Li CY, Yam LT, Crosby WH. Histochemical characteriza- Huygens grant H 93-155 from The Netherlands Organization tion of cellular and structural elements of the human for Scientific Research (NWO) to JB and grant NKI 88-13 from spleen. J Histocytochem 1972;20: 1049-58. the Dutch Cancer Society to FO. 27 Brenner MB, McLean J, Scheft H, Warnke RA, Jones N, We thank Remco Brandt, Carolien Bierman, Marga Rijken, Strominger JL. Characterization and expression of the Alexander van Leeuwen and the audiovisual department of the human a,B T cell receptor by using a framework mono- Rotterdam Cancer Center for expert technical assistance. clonal antibody. J Immunol 1987;138:1502-9. 28 Lawetzky A, Tiefenthaler G, Kubo R, Hfnig T. Identifica- tion and characterization of rat T cell subpopulations expressing T cell receptors a/# and y/6. Eur J Immunol 1990;20:343-9. 29 Sowder JT, Chen CH, Ager LL, Chan MM, Cooper MD. A 1 Davis MM, Bjorkman P. T-cell antigen receptor genes and large subpopulation of avian T cells express a homologue T-cell recognition. Nature 1988;334:395-402. of the mammalian T y/o receptor. J Exp Med 1988;167: 2 Brenner MB, Strominger J, Krangel MS. The yb T cell 315-22. receptor. Adv Immunol 1988;43:133-92. 30 Mackay CR, Beya M-F, Matzinger P. y/V T cells express a 3 Clevers H, Alarcon B, Wileman T, Terhorst C. The T cell unique surface molecule appearing late during thymic a ensemble. Ann development. Eur J Immunol 1989;19:1477-83. receptor/CD3 complex: dynamic protein http://jcp.bmj.com/ Rev Immunol 1988;6:629-62. 31 Mackay CR, Hein WR. A large proportion of bovine T cells 4 Chien Y, Iwashima M, Wettstein DA, et al. T-cell receptor express the yo T cell receptor and show a distinct tissue gene rearrangements in early thymocytes. Nature 1987; distribution and surface phenotype. Int Immunol 1989; 330:722-7. 1:540-5. 5 Havran WL, Allison JP. Developmentally ordered appear- 32 Hirt W, Saalmuller A, Reddehase MJ. Distinct y/o T cell ance of thymocytes expressing different T-cell antigen receptors define two subsets of circulating porcine CD2- receptors. Nature 1988;335:443-5. CD4-CD8- T lymphocytes. Eur JImmunol 1990;20:265. 6 Itohara S, Nakanishi N, Kanagawa 0, Kubo R, Tonegawa S. 33 Bucy RP, Chen CH, Cihak J, Losch U, Cooper MD. Avian Monoclonal antibodies specific to native murine T-cell T cells expressing yo receptors localize in the splenic receptor yo: analysis of yo T cells during thymic ontogeny sinusoids and in the intestinal epithelium. J Immunol and in peripheral lymphoid organs. Proc Natl Acad Sci 1988;141:2200-5. on October 1, 2021 by guest. Protected copyright. USA 1989;86:5094-9. 34 Havran WL, Allison JP. Origin of THY-i + dendritic 7 Stingl G, Koning F, Yamada H, et al. Thy-I' dendritic epidermal cells ofadult mice from fetal thymic precursors. epidermal cells express T3 antigen and the T-cell receptor Nature 1990;344:68. y chain. Proc Natl Acad Sci USA 1987;84:4586-90. 35 Ito K, Bonneville M, Takagaki Y, et al. Different yoT-cell 8 Bonyhadi M, Weiss A, Tucker PW, Tigelaar RE, Allison JP. receptors are expressed on thymocytes at different stages of Delta is the Cx-gene product in the y/6 antigen receptor of development. Proc Nati Acad Sci USA 1989;86:631-5. dendritic epidermal cells. Nature 1987;330:574-6. 36 Augustin A, Kubo RT, Sim G-K. Resident pulmonary 9 Itohara S, Farr AG, Lafaille JJ, et al. Homing of a yo lymphocytes expressing the yb T-cell receptor. Nature thymocyte subset with homogeneous T-cell receptors to 1989;340:239-41. mucosal epithelia. Nature 1990;343:754-7. 37 Carding SR, Kyes S, Jenkinson EJ, et al. Developmentally 10 Goodman T, Lefrancois L. Expression of the y-6 T cell regulated fetal thymic and extrathymic T-cell receptor yb receptor on intestinal CD8+ intraepithelial lymphocytes. gene expression. Genes Devel 1990;4:1304-15. Nature 1988;333:855-8. 38 Bandeira A, Mota-Santos T, Itohara S, et al. Localization of 11 Asarnow D, Goodman T, Lefrancois L, Allison JP. Distinct y/6 T cells to the intestinal epithelium is independent antigen receptor repertoires of two classes of murine of normal microbial localization. JExp Med 1990;172: epithelium-associated T cells. Nature 1989;341:60-2. 239-44. 12 Lafaille JJ, DeCloux A, Bonneville M, Takagaki Y, 39 Lefrancois L, Le Coue R, Mayo J, Bluestone JA, Goodman Tonegawa S. Junctional sequences of T cell receptor y5 T. Extrathymic selection of TCR yb + T cells by class II genes: implications for y6 T cell lineages and for a novel major histocompatibility complex molecules. Cell 1990; intermediate of V(D)-J joining. Cell 1989;59:859-70. 63:333-40.