Diversity of gamma delta T-cell receptors on murine intestinal intra-epithelial lymphocytes

T cell receptor delta gene repertoire and diversity of intestinal intraepithelial lymphocytes in athymic mice

T cell receptor (TCR) delta gene rearrangements in intestinal intraepithelial lymphocytes (IEL) were studied in athymic radiation chimeras using polymerase chain reaction (PCR) and sequence analysis of DNAs spanning the variable (V), diversity (D), and junctional (J) genes. In both thymus-bearing and athymic mice, IEL delta gene rearrangements occurred for V delta 3, V delta 4, V delta 5 and V delta 6. V-D-J junctional-site sequence analyses of cloned DNAs from rearranged IEL delta genes in athymic mice revealed a predominance of in-frame rearrangements; junctional diversity consisting of nucleotide removal from V, D and/or J genes; N segment nucleotide insertions; and high overall gene diversity. Evaluation of PCR-amplified cDNAs made from IEL RNA indicated that all four rearranged V delta genes were expressed in IEL from athymic mice. The high diversity observed at the gene level also was present in amino acid sequences encoded by the V-D-J region of IEL delta genes in athymic mice. These data demonstrate that there is extensive diversity of rearranged delta genes in IEL which develop extrathymically, and suggest that the delta chain of IEL TCR-gamma delta+ T cells has the potential for interactions with polymorphic structures.

Listeria monocytogenes-induced gamma interferon secretion by intestinal intraepithelial gamma/delta T lymphocytes

gamma/delta T cells represent a major proportion of intestinal intraepithelial lymphocytes (IEL), and it has been suggested that these IEL serve as a first immune barrier against microbial invasion and that they do so by destroying infected epithelial cells. In the present study, we confirm that both alpha/beta and gamma/delta IEL from naive mice express potent cytotoxicity and produce gamma interferon (IFN-gamma) after T-cell receptor (TCR) engagement by specific monoclonal antibodies (MAb). Intraperitoneal administration of the anti-gamma/delta TCR MAb GL3 caused downregulation of the gamma/delta TCR in IEL, and IEL from gamma/delta TCR-modulated mice failed to express cytotoxic activity and to secrete IFN-gamma after gamma/delta TCR engagement. In contrast, alpha/beta IEL from such mice were still cytolytic and secreted IFN-gamma. Mice were infected orally with virulent Listeria monocytogenes at doses which caused bacterial invasion through the intestinal epithelia. Although alpha/beta and gamma/delta IEL from these mice expressed high cytolytic activities in antibody-redirected killer assays, target cells pulsed with listerial antigens were not lysed. In contrast, IFN-gamma secretion by IEL from L. monocytogenes-infected mice was induced not only by anti-TCR MAb but also by target cells pulsed with listerial antigens, whereas irrelevant antigens, including heat shock protein 60, did not induce IFN-gamma secretion. Furthermore, the number of IFN-gamma-secreting IEL, as assessed by the enzyme-linked immunospot technique, was increased during listeriosis. gamma/delta TCR modulation by GL3 administration abrogated antigen-induced IFN-gamma secretion by IEL from infected mice. These findings suggest that L. monocytogenes induced IFN-gamma secretion by gamma/delta IEL from mice suffering from intestinal L. monocytogenes infection and invasion. Thus, the data provide evidence for a role of IFN-gamma-secreting IEL in local resistance against listeriosis and perhaps other food-borne diseases.

Peripheral selection of antigen receptor junctional features in a major human gamma delta subset

Recent studies demonstrating the existence of murine gamma delta T cell subsets with structurally identical T cell receptors (TcR) suggest that unlike alpha beta T cells, some gamma delta T cells are specialized in the recognition of a limited number of monomorphic antigens. However, this question still remains open in humans, since the TcR structural diversity of their peripheral gamma delta T cells was shown to be extensive. Here we have analyzed in detail the TcR chain genes expressed by human V gamma 9+V delta 2+ peripheral blood lymphocytes (PBL), a major peripheral gamma delta T cell subset in adults and present evidence for an antigen-driven peripheral selection of both TcR gamma and delta junctional motifs among these cells. First, it is shown that the proportion of V gamma 9+V delta 2+ cells expressing the V9JPC1 gamma chain is much higher among PBL than among thymus-derived clones, indicating that preferential use of this J gamma segment is not due to pairing or combinatorial constraints. Second, analysis of V9JPC1 gamma transcripts derived from V gamma 9+V delta 2+ PBL clones revealed a high prevalence of a unique V9JP gamma sequence with limited "N" nucleotide additions and VJ trimming, which could not be accounted for by enzymatic or antigen-independent structural limitations. Third, the TcR delta chain expressed by most V gamma 9+V delta 2+ PBL clones, though diverse in amino acid composition and length, carried a highly distinctive junctional motif, found at a much lower frequency among V2DJ delta sequences derived from V gamma 9-V delta 2+ PBL or V gamma 9+V delta 2+ thymocytes. Together, these results which demonstrate shared gamma and delta junctional features by cells using unique V gamma and V delta genes, suggest that in vivo selection of V gamma 9+V delta 2+ lymphocytes is mediated by a highly restricted number of nominal ligands.

Ordered rearrangement of variable region genes of the T cell receptor gamma locus correlates with transcription of the unrearranged genes

T cell receptor V gamma genes rearrange to the J gamma 1 gene segment in a highly ordered fashion during development. We demonstrate a striking correlation between the pattern of expression of unrearranged V gamma genes and the timing of their rearrangement. Thus, the increases in V gamma 2 rearrangements, and decreases in V gamma 3 and V gamma 4 rearrangements observed during development are paralleled by increasing or decreasing levels of the corresponding unrearranged V gene transcript. We also provide evidence that both the V gamma 3 and V gamma 4 genes are accessible in mature V gamma 3+ cells, but that the V gamma 4 gene may be inaccessible in the progenitors of V gamma 3 cells. The results suggest that regulated local accessibility of the chromatin surrounding V gamma genes is responsible for ordered V gamma gene rearrangement during development.

Human fetal liver gamma/delta T cells predominantly use unusual rearrangements of the T cell receptor delta and gamma loci expressed on both CD4+CD8- and CD4-CD8- gamma/delta T cells

Substantial numbers of both alpha/beta and gamma/delta T cells are present in human fetal liver, which suggests a role of the fetal liver in T cell development. The diversity of fetal liver T cell receptor (TCR) gamma and delta chain rearrangements was examined among both CD4+CD8- and CD4-CD8- gamma/delta T cell clones. In addition, TCR delta chain transcripts from three fetal livers were sequenced after polymerase chain reaction amplification of TCR delta chains with V delta 1 or V delta 2 rearrangements. Five of six fetal liver gamma/delta T cell clones had a V delta 2-D delta 3-J delta 3 gene rearrangement with limited junctional diversity; three of these clones had an unusual CD4+CD8- phenotype. V delta 2-D delta 3-J delta 3 gene rearrangements were also common among both in-frame and out-of-frame transcripts from three fetal livers, indicating that they are the result of an ordered rearrangement process. TCR gamma chain sequences of the fetal liver gamma/delta T cell clones revealed V gamma 1-J gamma 2.3, V gamma 2-J gamma 1.2, and V gamma 3-J gamma 1.1 rearrangements with minimal incorporation of template-independent N region nucleotides. TCR gamma chain rearrangements found in these fetal liver T cell clones were different from those that have been observed among early thymic gamma/delta T cell populations, while similar TCR delta chain rearrangements are found among gamma/delta T cells from both sites. These data demonstrate that the fetal liver harbors gamma/delta T cell populations distinct from those found in the fetal thymus, suggesting that the fetal liver is a site of gamma/delta T cell development in humans. These unusual T cell populations may serve a specific function in the fetal immune system.

Compartmentalization of the peripheral immune system

The periphery of the immune system--as opposed to the central lymphoid organs--contains inhomogeneously distributed B and T cells whose phenotype, repertoire, developmental origin, and function are highly divergent. Nonconventional lymphocytes bearing a phenotype that is rare in the blood, spleen, or lymph nodes of undiseased individuals are encountered at high frequency in different localizations, e.g., alpha/beta TCR+CD4-CD8- cells in the bone marrow and gut epithelium, particular invariant gamma/delta TCR+CD4-CD8 alpha+CD8 beta- and gamma/delta TCR+CD4-CD8 alpha-CD8 beta- T cells in various epithelia, or CD5+ B cells in the peritoneum. The antigen receptor repertoire is different in each localization. Thus, different gamma/delta TCR gene products dominant in each site, and the proportion of cells expressing transgenic and endogenous alpha/beta TCR and immunoglobulin gene products follows a gradient, with a maximum of endogenous gene expression in the peritoneum, intermediate values in other peripheral lymphoid organs (spleen, lymph nodes), and minimum values in thymus and bone marrow. Forbidden T cells that bear self-superantigen-reactive V beta gene products are physiologically detected among alpha/beta TCR+CD4-CD8- lymphocytes of the bone marrow, as well as in the gut. Violating previous ideas on self-tolerance preservation, self-peptide-specific gamma/delta T cells are present among intestinal intraepithelial lymphocytes, and CD5+ B cells produce low-affinity crossreactive autoantibodies in a physiological fashion. It appears that, in contrast to the bulk of T and B lymphocytes, certain gamma/delta and alpha/beta T cells found in the periphery, as well as most CD5+ B cells, do not depend on the thymus or bone marrow for their development, respectively, but arise from different, nonconventional lineages. In addition to divergent lineages that are targeted to different organs guided by a spatiotemporal sequence of tissue-specific homing receptors, local induction or selection processes may be important in the diversification of peripheral lymphocyte compartments. Selection may be exerted by local antigens, antigen-presenting cells whose function varies in each anatomical localization, cytokines, and cell-matrix interactions, thus leading to the expansion and maintenance of some clones, whereas others are diluted out or deleted. The spatial compartmentalization of lymphocytes in different microenvironments has major functional consequences and leads to a partial fragmentation of immunoregulatory circuits at the local level. Lymphocytes residing in certain antigen-exposed compartments are likely to combat tissue-specific pathogens or self-proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

MHC class I-deficient mice

A great deal has already been learned from the analysis of beta 2m-mutant mice, but it is clear that a great deal remains to be learned. A significant (though unanticipated) problem with this model system is that it is functionally leaky: residual functional class I expression can be detected in beta 2m- mice, and small numbers of functional CD8+ lymphocytes are present in the animals. In many cases, this has frustrated the initial attempts at obtaining immediate definitive resolution of important questions regarding the function of class I molecules. This has occurred primarily in instances in which the class I-deficient mice fail to express an expected phenotype--for example, in studies showing that beta 2m- mice make adequate protective immune responses against certain intracellular pathogens, and are able to reject some allogeneic tissues with a relatively normal pace. On the other hand, it appears that combining the use of beta 2m- mice with other methods (for example, antibody-mediated depletion of CD8+ T cells) is usually adequate to circumvent these difficulties. It remains to be seen whether other better class I deficiencies can be engineered--for example, large deletions of class I genes or mutations in transcription factors essential for class I gene expression. The extent of immunocompetence of beta 2m- mice was somewhat surprising. It was widely expected that class I-deficient mice would be exquisitely sensitive to many viral infections, though the results indicate that sensitivity varies dramatically with the virus and conditions of infection. However, it appears that in lieu of one major arm of the immune system, compensatory immune mechanisms are in many cases able to deal with infection. Similar conclusions are developing from the analysis of several other recently generated mutant mice. Nevertheless, the results indicate a very important role for class I-directed responses in clearing infections mediated by various viral and parasitic agents, particularly in the case of more severe conditions of infection. Although the class I-deficient mice were initially considered primarily a vehicle for analysis of the role of CD8+ T cells, evidence is accumulating that they manifest deficiencies in several other types of lymphocytes, including NK cells, TCR alpha beta+CD4-CD8- cells, and a subset of TCR gamma delta+ cells. This has been a boon for analysis of the development of these cells, but at the same time it has created difficulties in assigning a biological effect of the mutation to a specific lymphocyte deficiency.(ABSTRACT TRUNCATED AT 400 WORDS)

New T-cell receptor gamma haplotypes in wild mice and evidence for limited Tcrg-V gene polymorphism

Tcrg gene polymorphism was investigated by Southern blot analysis on a panel of laboratory and wild mouse strains using a set of probes which identify all known Tcrg-V and -C genes. Only three haplotypes are found in laboratory mice: gA, gB, and gC which are represented by BALB/c, AKR, and DBA/2 prototypes respectively. gA and gC haplotypes are the most frequent among laboratory mice whereas gB is poorly represented. Seven new haplotypes are described among 23 wild mice corresponding to four Mus musculus subspecies (Mus mus domesticus, castaneus, musculus, and molossinus). However, only a few new alleles of individual genes are observed. Tcrg-V genes located at the 5' end of the Tcrg locus (V7 and V4) appear to be nonpolymorphic whereas two Tcrg-V3, -V5, -V6, -C4 and three Tcrg-V1, -V2, -C1, -C2, and -C3 specific restriction fragment length polymorphisms are detected. These results indicate a relatively high degree of conservation of Tcrg genes as compared to other members of the immunoglogulin (Ig) gene family and might be related to the specifity and function of gamma delta T cells. Several of the new haplotypes described here result from point mutations in noncoding Tcrg-V or -C gene-flanking regions. Recombinations may have also participated in the evolution of the Tcrg locus. Finally, these new Tcrg haplotypes are unequally distributed among the four M. m. subspecies and support the idea that the gA and gC haplotypes found in laboratory mice are inherited from M. m. domesticus whereas gB might originate from asian subspecies (castaneus, musculus or molossinus).

Expression of T cell receptors alpha beta and gamma delta in the ileal mucosa of patients with Crohn's disease and with spondylarthropathy

The expression of the alpha beta and gamma delta heterodimer of the T cell receptor (TCR) was studied in normal human ileal mucosa or in ileal biopsies featuring Crohn's disease or acute and chronic spondylarthropathy-related gut inflammation. With an immunohistochemical technique we demonstrated that the increase of mucosal lymphocytes per mm mucosa in Crohn's disease and spondylarthropathy-related ileitis is exclusively due to expansion of the alpha beta + T cell compartment. In Crohn's disease and chronic ileitis observed in some spondylarthropathy patients the alpha beta + T cells were increased amongst intraepithelial lymphocytes (IEL). The lamina propria lymphocytes (LPL) were augmented in all studied inflammatory conditions. The gamma delta + T cells showed no changes in IEL or LPL and their proportions were not altered. They were evenly dispersed throughout the ileal mucosa and did not seem to participate in the inflammatory process. This study confirms that gamma delta T cells are a distinct subset in the intestinal mucosa. The increase in alpha beta + T cells suggests augmented mucosal antigen handling and involvement of the major histocompatibility complex in the pathogenesis of spondylarthropathy-related gut inflammation and Crohn's disease.

Development and selection of gamma delta T cells

The gamma delta T-cell population, a subpopulation of T cells formed through cell lineages that are independent of the alpha beta T-cell lineage, consists of multiple subsets with distinct receptor repertoires and homing properties. While the cell sublineage is a critical factor in the determination of homing specificity, both cell sublineage and receptor-dependent selection are instrumental in the determination of the functional repertoire.

Mouse autoreactive gamma/delta T cells. I. Functional properties of autoreactive T cell hybridomas

A minor population of dendritic epidermal T cells (DETC) express the V gamma 1.1C gamma 4V delta 6 T cell receptor and T cell clones and hybridomas derived from this subset constitutively secrete cytokines in culture secondary to recognition of an autoantigen. Activation of these autoreactive cells requires the use of the vitronection receptor (VNR) as an accessory molecule which interacts with the Arg-Gly-Asp-Ser (RGDS) sequence of extracellular matrix (ECM) proteins. We have compared the functional properties of C gamma 4+ hybridomas derived from newborn thymocytes and from adult spleen with the DETC hybridomas/lines in terms of their ability to secrete cytokines spontaneously and for the use of the VNR as an accessory molecule. Almost all the C gamma 4+ thymocyte hybridomas secreted cytokines spontaneously and in the majority of lines the most prominent cytokine secreted was granulocyte-monocyte colony-stimulating factor. In contrast, none of the four splenic C gamma 4+ hybridomas secreted cytokines spontaneously although all were capable of cytokine production following activation via the T cell receptor. Although the thymocyte hybridomas did not grow as adherent cell lines in culture, constitutive cytokine production required engagement of the VNR by its ligand in ECM proteins. In all cases, cytokine production could be inhibited by an anti-VNR monoclonal antibody as well as by soluble RGDS. The strong correlation of functional and molecular properties between thymocyte C gamma 4+ hybridomas and C gamma 4+ DETC suggests that the C gamma 4+ DETC may be of thymic origin and that cells with potential for autoreactivity residing in the thymus at birth may populate other peripheral locations in the mouse. The data also support the concept that the VNR, and possibly other integrins, play a role as accessory elements for autoreactive cells and may be essential for the regulation of such activity.

Identification of a soluble GM-CSF binding protein in the supernatant of a human choriocarcinoma cell line

We identified two forms of the receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) made by the human choriocarcinoma cell line JEG-3 using an affinity-labeling technique. The protein was identified in the detergent-extract was 78 kDa, very similar to that of the membrane-bound GM-CSF receptor alpha chain expressed in a wide variety of hematopoietic and nonhematopoietic cells, including JEG-3. In contrast, a 62-kDa GM-CSF binding protein, or the soluble GM-CSF receptor, was identified in the supernatant of JEG-3 cells. Utilizing the same affinity labeling technique, we did not detect the soluble GM-CSF binding protein in the supernatant of several hematopoietic cell lines, such as U-937 and KG-1, which express membrane bound alpha chain as well as beta chain. The 62-kDa soluble GM-CSF receptor is produced in abundant amounts by JEG-3, but in very small amounts, if any, by hematopoietic cell lines.

Age-associated increase in number of CD4+CD8+ intestinal intraepithelial lymphocytes in rats

A significant number of CD4+CD8+ T cells were detected in intestinal intraepithelial lymphocytes (IEL) of various strains of rats including Wistar, WKA, BN, LEW and F344. The site of the CD4+CD8+ population in IEL increased with age in all strains we examined. Most IEL bearing CD8 expressed no CD5 antigen in young rats, while all CD4+CD8+ IEL and some of CD8+ IEL in aged rats were of CD5+CD45RB- phenotype. In germ-free Wistar rats, age-associated increase in the number of CD4+CD8+CD5+ IEL was not evident, indicating that stimulation by the intestinal microflora was important for expansion of the CD4+CD8+CD5+CD45RB- IEL. Aged athymic F344 nude rats contained appreciable numbers of CD4+ IEL and CD8+ IEL but few CD4+CD8+ IEL, suggesting that the CD4+CD8+ IEL may be derived from thymus-dependent populations. Unlike a majority of CD4+CD8+ thymocytes bearing a low intensity of CD3/T cell receptor (TcR) alpha/beta, the CD4+CD8+ T cells in IEL expressed a high intensity of CD3/TcR alpha/beta on their surface. The CD4+CD8+ IEL appear to contribute to the spontaneous proliferation of the IEL in aged rats as assessed by tritiated thymidine incorporation after in vitro culture with medium only. These results suggest that with aging a unique CD4+CD8+ IEL may expand at a local site of the intestine under the influence of intestinal microflora and may contribute to the first line of defense against various pathogens in the epithelium.

Extrathymic origin of V gamma 1/V delta 6 T cells in the skin

The dendritic epidermal cells (dEC) from young (8-week-old) athymic mice were found to express mRNA for gamma/delta T cell receptors (TcR). The mRNA found in the dEC from athymic mice was expressed only for V gamma 1-J gamma 4-C gamma 4 and V delta 6-J delta 1-C delta with both chains having productive rearrangements and junctional diversity. On the other hand, the dEC from euthymic mice carried V gamma 5-J gamma 1-C gamma 1 and V delta 1-J delta 2-C delta in addition to the V gamma 1/V delta 6 subset found in athymic mice. Therefore, this V gamma 1/V delta 6 subset, which has been implicated in the murine gamma/delta T cell responses to mycobacterial antigens and self heat-shock proteins, is the product of extrathymic maturation in the dEC from both athymic and euthymic mice.

Intestinal intraepithelial lymphocyte T cells are resistant to Ipr gene-induced T cell abnormalities

The mucosal immune system of the gastrointestinal (GI) tract consists of Peyer's patches (PP), which are IgA inductive sites, and more diffuse effector regions which include cells in the intraepithelial lymphocyte (IEL) compartment. Since autoimmune MRL lpr/lpr (MRL/lpr) mice develop a proliferating CD3+, CD4-, CD8- (double negative; DN), B220+ T cell subset in systemic lymphoid tissue, we have initiated studies to determine the distribution of CD3+, DN, B220+ T cells (B220+ T cells or lpr/lpr T cells) in the GI immune system. Specifically, we examined T cell subsets separated according to expression of CD4, CD8, Thy-1, B220, alpha/beta T cell receptor (TcR) and gamma/delta TcR in PP and IEL of MRL/lpr mice at 6, 12 and 21 weeks of age. Increased numbers of CD3+ T cells were noted in both PP and spleen of 12- and 21-week-old mice in which the development of autoimmune disorders were also evident. However, normal numbers of CD3+ IEL T cells were seen in MRL/lpr mice in all three age groups tested. When the presence of T cell lymphadenopathy was examined in both IgA inductive and effector tissues, the PP followed the B220+ T cell pattern seen in the spleen, where approximately 30%-50% of CD3+ T cells in the PP of 12- and 21-week-old MRL/lpr mice expressed the phenotype of lpr/lpr T cells and greater than 90% were alpha/beta TcR+. On the other hand, B220+ T cells had not developed in PP or spleen of 6-week-old MRL/lpr mice. Of interest was the finding that IEL from lpr/lpr homozygous mice did not contain B220+ T cells in any age group tested. In this regard, the IEL of MRL/lpr mice comprised an identical pattern and frequency of CD4-/CD8+, CD4+/CD8-, DN and CD4+/CD8+ (double positive, DP) T cell subsets as their normal counterparts (i.e. MRL +/+, BALB/c and C3H/HeN mice) which consisted of approximately 75%, approximately 7.5%, approximately 7.5% and approximately 10%, respectively. Further, Thy-1, gamma/delta TcR and alpha/beta TcR expression in these four subsets of MRL/lpr IEL were very similar to normal mice. These results suggest that the intestinal IEL compartment is minimally affected by the lpr/lpr mutation which induces T cell abnormalities and indicate that B220+ T cells do not preferentially home to IEL. Further, our results support the concept that IEL T cells develop as a separate T cell lineage from thymus-derived cells.

Rearrangement and junctional-site sequence analyses of T-cell receptor gamma genes in intestinal intraepithelial lymphocytes from murine athymic chimeras

The molecular organization of rearranged T-cell receptor (TCR) gamma genes intraepithelial lymphocytes (IEL) was studied in athymic radiation chimeras and was compared with the organization of gamma gene rearrangements in IEL from thymus-bearing animals by polymerase chain reaction and by sequence analyses of DNA spanning the junction of the variable (V) and joining (J) genes. In both thymus-bearing mice and athymic chimeras, IEL V-J gamma-gene rearrangements occurred for V gamma 1.2, V gamma 2, and V gamma 5 but not for V gamma 3 or V gamma 4. Sequence analyses of cloned V-J polymerase chain reaction-amplified products indicated that in both thymus-bearing mice and athymic chimeras, rearrangement of V gamma 1.2 and V gamma 5 resulted in in-frame as well as out-of-frame genes, whereas nearly all V gamma 2 rearrangements were out of frame from either type of animal. V-segment nucleotide removal occurred in most V gamma 1.2, V gamma 2, and V gamma 5 rearrangements; J-segment nucleotide removal was common in V gamma 1.2 but not in V gamma 2 or V gamma 5 rearrangements. N-segment nucleotide insertions were present in V gamma 1.2, V gamma 2, and V gamma 5 IEL rearrangements in both thymus-bearing mice and athymic chimeras, resulting in a predominant in-frame sequence for V gamma 5 and a predominant out-of-frame sequence for V gamma 2 genes. These findings demonstrate that (i) TCR gamma-gene rearrangement occurs extrathymically in IEL, (ii) rearrangements of TCR gamma genes involve the same V gene regardless of thymus influence; and (iii) the thymus does not determine the degree to which functional or nonfunctional rearrangements occur in IEL.

Tissue distribution of human gamma delta T cells: no evidence for general epithelial tropism

In man and mice only a small proportion of T cells in the peripheral lymphoid compartment express the gamma delta T cell receptor (TCR). In mice, however, gamma delta T cells comprise the predominant population at particular epithelial sites--in epidermis and epithelia of intestine, reproductive organs, and tongue. The distribution of gamma delta T cells in normal human tissues was investigated, paying particular attention to epithelial layers. In all lymphatic organs and in epithelia of a wide variety of non-lymphatic organs, including the respiratory tract, male and female reproductive organs and tongue, gamma delta T cells constituted less than 5% of total T cells, with the remainder expressing TCR alpha beta. The only exception was the intestine, where gamma delta T cells were preferentially situated in the columnar epithelium of the crypts, rather than in the lamina propria. It is concluded, therefore, that human gamma delta T cells do not display a general epithelial tropism and are, in terms of relative numbers, no more able than alpha beta T cells to carry out continuous surveillance of the immune system against infection or transformation in epithelia. gamma delta T cells may, however, have a specialised function in the epithelium of the intestinal tract.

IL-2-dependent murine T-cell lines and clones expressing gamma/delta T-cell antigen receptors. I. Functional and biochemical characterization

We have developed two stable IL-2-dependent T-cell lines designated AKV-I and AKV-N from the enlarged spleens, respectively, of an AKV1 and an NFS mouse. Immunofluorescence staining with the appropriate monoclonal antibodies revealed that cells of the AKV-I cell line were alpha beta TCR-CD3+CD4-CD5-CD8+CD25+, whereas cells of the AKV-N cell line were alpha beta TCR-CD3+CD4-CD5+CD8-CD25+. A number of T-cell clones were developed from the AKV-I or AKV-N T-cell lines by limiting dilution and analysed by immunofluorescence. All clones tested were alpha beta TCR-CD3+CD4-CD25+. Certain T-cell clones expressed the CD5 antigen, whereas others expressed the CD8 antigen. The AKV-I cell line responded by proliferation to rIL2, rIL4, phorbol myristate acetate (PMA), PMA plus IL-4 and PMA plus PHA or Con A. In contrast, the AKV-N cell line did not respond to rIL-4 or rIL-4 plus PMA and exhibited only a modest proliferative response to PMA alone. Both AKV-I and AKV-N T-cell lines as well as a large number of T-cell clones examined were able to lyse cells of the PU5-IR murine cell line in the presence of the anti-CD3 (clone 145-2C11) MoAb, demonstrating their ability to mediate cytotoxicity in this system. Biochemical analysis of both AKV lines and a number of clones by immunoprecipitation with the anti-CD3 MoAb, followed by one-dimensional (either non-reducing or reducing) or two-dimensional (non-reducing/reducing) SDS-PAGE, revealed that the AKV lines and clones expressed a disulphide-linked dimer. Under non-reducing conditions, a band in the range of 75-85 kDa was observed and upon reduction it was resolved into two discrete polypeptide chains of 43-44 kDa and 48 kDa in certain AKV-I cells or 38 kDa and 42 kDa in certain AKV-N cells. In other T-cell clones or lines a broad band of 42-47 kDa was observed in AKV-I cells or 38-45 kDa in AKV-N cells. These results suggest the presence of different forms of disulphide-linked dimers on these cells. Northern blotting analysis using probes specific for the constant regions of the alpha-, beta-, gamma- and delta-chains of the T-cell antigen receptor revealed that all the AKV cell lines or clones tested expressed full-length alpha-, gamma- and delta-chain mRNA, whereas beta-chain mRNA was absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Rearrangement and junctional-site sequence analyses of T-cell receptor gamma genes in intestinal intraepithelial lymphocytes from murine athymic chimeras

The molecular organization of rearranged T-cell receptor (TCR) gamma genes intraepithelial lymphocytes (IEL) was studied in athymic radiation chimeras and was compared with the organization of gamma gene rearrangements in IEL from thymus-bearing animals by polymerase chain reaction and by sequence analyses of DNA spanning the junction of the variable (V) and joining (J) genes. In both thymus-bearing mice and athymic chimeras, IEL V-J gamma-gene rearrangements occurred for V gamma 1.2, V gamma 2, and V gamma 5 but not for V gamma 3 or V gamma 4. Sequence analyses of cloned V-J polymerase chain reaction-amplified products indicated that in both thymus-bearing mice and athymic chimeras, rearrangement of V gamma 1.2 and V gamma 5 resulted in in-frame as well as out-of-frame genes, whereas nearly all V gamma 2 rearrangements were out of frame from either type of animal. V-segment nucleotide removal occurred in most V gamma 1.2, V gamma 2, and V gamma 5 rearrangements; J-segment nucleotide removal was common in V gamma 1.2 but not in V gamma 2 or V gamma 5 rearrangements. N-segment nucleotide insertions were present in V gamma 1.2, V gamma 2, and V gamma 5 IEL rearrangements in both thymus-bearing mice and athymic chimeras, resulting in a predominant in-frame sequence for V gamma 5 and a predominant out-of-frame sequence for V gamma 2 genes. These findings demonstrate that (i) TCR gamma-gene rearrangement occurs extrathymically in IEL, (ii) rearrangements of TCR gamma genes involve the same V gene regardless of thymus influence; and (iii) the thymus does not determine the degree to which functional or nonfunctional rearrangements occur in IEL.

In vivo induction of gamma/delta T cells with highly potent and selective anti-tumor cytotoxicity

High frequencies of CD5+TcR alpha/beta- T cells were induced in the peritoneal cavity of rats immunized with syngeneic W439 lymphoma cells. These TcR alpha/beta- cells expressed TcR delta mRNA as analyzed by the polymerase chain reaction technique. The delta + (TcR gamma/delta +) T cells were of the CD2+, CD3+, CD4-, CD8+, CD45RB+ phenotype and showed stronger anti-tumor cytotoxicity compared to the TcR alpha/beta + T cells. The cytotoxic effects of both alpha/beta and gamma/delta T cells were selective for the W439 lymphoma cells and were not directed to other syngeneic tumors, natural killer targets and syngeneic or allogeneic normal cells. T cells, including both alpha/beta and gamma/delta cells, were induced when WF rats were immunized with allogeneic BN spleen cells. In this case the gamma/delta T cells showed allo-selective cytotoxicity, although weaker compared to the TcR alpha/beta + T cells. The gamma/delta T cells, induced by immunization with either W439 cells or BN spleen cells, were selective for the immunogen used and had no effect on irrelevant target cells, indicating that these effector cells were not activated by a shared gamma/delta T cell-related superantigen. Since highly potent tumor-selective gamma/delta cytotoxic T lymphocytes could be induced by syngeneic lymphoma cells, we suggest a role for gamma/delta T cells in the defense against certain types of tumors.

Reciprocal T cell responses in the liver and thymus of mice injected with syngeneic tumor cells

We investigated the T cell responses in various tissues, especially in the liver and thymus, of mice injected with syngeneic tumors. This study was undertaken since recent evidence indicated that the liver is one of the important immune organs for T cell proliferation. When C3H/He mice were intraperitoneally injected with mitomycin-treated syngeneic MH134 tumors (1 x 10(7)/mouse), a transient increase of liver mononuclear cells (MNC) was induced, showing a peak at Day 4 after injection. Histological study of such liver showed a sinusoidal dilatation and an accumulation of MNC in the sinusoids. The most predominant MNC induced were double negative (CD4-8-) alpha beta T cells and gamma delta T cells. These gamma delta T cells varied, showing unique time-kinetics. Despite a continuous increase of whole liver MNC and alpha beta T cells, the proportion of gamma delta T cells in the liver decreased beginning 4 days after injection. In contrast with the response in the liver, a striking decrease in the cell number of thymocytes was induced after tumor injection, showing a basal level at Day 6. This hypocellularity in the thymus appears to be an inverted response of the lymphocytosis in the liver. At this time, a corresponding decrease in the proportion of double positive (CD4+8+) T cells was always seen in the thymus. Analysis of cell proliferative response showed that the increase of liver MNC after tumor injection was accompanied by augmented proliferation, whereas the decrease of thymocytes was accompanied by depressed proliferation. The present results indicate that there exists a unique, reciprocal response of T lymphocytes between the liver and thymus, and that the presence of tumor appears to stimulate T cell response in the liver but alternatively inactivates such response in the thymus.

Oligoclonal expansion and CD1 recognition by human intestinal intraepithelial lymphocytes

A human intestinal intraepithelial lymphocyte (IEL) T cell line was established from jejunum to characterize the structure and function of the alpha beta T cell antigen receptors (TCRs) expressed by this population. Single-sided polymerase chain reaction (PCR) amplification cloning and quantitative PCR amplification of the TCR chains from the cell line and from fresh IELs demonstrated that IELs were oligoclonal. The IEL T cell line exhibited CD1-specific cytotoxicity and a dominant IEL T cell clone was CD1c-specific. Thus, human jejunal intraepithelial lymphocytes are oligoclonal and recognize members of the CD1 gene family.

Evidence for clonal selection of gamma/delta T cells in response to a human pathogen

T cells bearing gamma/delta antigen receptors comprise a resident population of intraepithelial lymphocytes in organs such as skin, gut, and lungs, where they are strategically located to contribute to the initial defense against infection. An important unsolved question about antigen-driven gamma/delta T cell responses regards the breadth of their T cell receptor (TCR) repertoire, since many specific epithelial compartments in mice display limited diversity. We have examined the diversity of TCR delta gene expression among human gamma/delta T cells from skin lesions induced by intradermal challenge with Mycobacterium leprae. We show that the vast majority of gamma/delta cells from M. leprae lesions use either V delta 1-J delta 1 or V delta 2-J delta 1 gene rearrangements and, within a given region of the lesion, display limited junctional diversity. This contrasts markedly with the extensive diversity of gamma/delta T cells from peripheral blood of these same individuals, as well as skin from normal donors. These results indicate that the gamma/delta response to M. leprae involves the selection of a limited number of clones from among a diverse repertoire, probably in response to specific mycobacterial and/or host antigens.

Influence of site of expression on the fetal gamma delta T-cell receptor repertoire

The sequences of productive T-cell gamma/delta receptor transcripts were compared in different murine fetal tissues. Differences from tissue to tissue suggest that the sequence repertoires are at least in part the products of selection, presumably through interaction of T cells bearing the gamma delta receptor with fetal self-ligands.

Highly restricted expression of the thymus leukemia antigens on intestinal epithelial cells

The TL region of the major histocompatibility complex of the mouse contains dozens of tandemly arranged class I genes, including those encoding the thymus leukemia (TL) antigens. TL antigens have been thought to be expressed only on the surface of some T lineage cells, namely immature thymocytes of some mouse strains (TL+ strains), some leukemia cells, and activated T cells. While the function of TL antigens is unknown, recent studies have implicated the products of at least some TL region class I genes as molecules that present antigens to gamma/delta T cells. Since some gamma/delta T cells are known to be specifically associated with certain epithelial tissues, we have investigated the expression of some TL region class I genes in a variety of epithelium-containing tissues. Our results show that the TL antigen gene of C57BL/6 mice, T3b, and the TL antigen genes of BALB/c mice, T3d (previously T3c) and T18d (previously T13c), are highly expressed in the epithelium of the small intestine. In the case of T3b, we further show, using a T3 product-specific antibody, that its product is expressed on the surface of the columnar epithelial cells. In addition, we demonstrated that two other TL region class I genes of C57BL/6 origin, T9b and T21b, are also expressed nearly exclusively in intestinal epithelial cells. These results are consistent with the hypothesis that the products of these TL region class I genes are recognized by gamma/delta T cell receptors of intestinal intraepithelial lymphocytes, a subset of gamma/delta T cells that is localized in the intestinal epithelium and has a restricted V gamma repertoire. Finally, our study indicates that the relative levels of expression of the two homologous TL antigen genes, T3d and T18d, differ widely between the thymus and the intestine.

Ontogeny of the response of mouse thymocytes to interleukin 1 and interleukin 2

In the present report we demonstrate that the in vitro proliferative response of the newborn thymocytes to interleukin (IL) 1 and IL 2, which is remarkably stronger than the adult thymocyte response, is associated with a considerable increase of CD4-CD8- cells expressing a gamma/delta T cell receptor (TcR). By polymerase chain reaction analysis we show that the V gamma gene segment usage in the adult and newborn responding cells reflects the developmentally regulated expression of the V gamma gene segments, suggesting that the increase in TcR gamma/delta+ cells results from the polyclonal expansion of pre-existing clones. Surprisingly, although the fetal thymocyte populations contain higher numbers of TcR gamma/delta+ cells than the adult and newborn ones, the highest proliferative response to IL 1 and IL 2 is obtained with the newborn thymocytes. Non mutually exclusive hypotheses are discussed to explain these results.

Predominant appearance of gamma/delta T lymphocytes in the liver of mice after birth

gamma/delta T lymphocytes residing in the liver of mice were systematically characterized with respect to their age-related variation, phenotype and V gene segment usage of gamma/delta T cell receptor (TcR). Previous human and murine studies have shown that a high proportion of gamma/delta T cells reside in the liver and that such liver gamma/delta T cells have lymphoblastic morphology and can spontaneously proliferate in vitro. In the present study, a predominant appearance of gamma/delta T cells (up to 23% among CD3+ cells) in the liver was confirmed in 4-week old mice of various strains. gamma/delta T cells in the liver preferentially co-expressed CD8 antigens, whereas the vast majority of gamma/delta T cells in the spleen lacked the CD8 antigens. The identification of gamma/delta T cells in various lymphoid and non-lymphoid organs also revealed the liver to be one of the organs where gamma/delta T cell are most abundant. The level of such liver gamma/delta T cells showed a clear age-related variation. In the fetal stage and just after birth, gamma/delta T cells were not detectable in the liver (less than 0.2%). However, a significantly higher percentage of gamma/delta T cells among both the total population of mononuclear cells and CD3+ cells was detected in the liver of young 2- to 8-week-old mice; this percentage subsequently declined. As the total number of liver mononuclear cells increased in aged mice, the absolute number of liver gamma/delta T cells also increased as a function of age. V gene segment usage analysis by the polymerase chain reaction method demonstrated that V gamma 1 or V gamma 2/V delta 6 were preferentially used by liver gamma/delta T cells. The age-related increase of gamma/delta T cells was more prominent in the liver of athymic nude mice, and such gamma/delta T cells highly co-expressed the CD8 antigens and also utilized the V gamma 1 or V gamma 2/V delta 6 for gamma/delta Tcr. The predominant appearance of unique gamma/delta T cells in the liver, which was inversely related to the existence of the thymus, indicates that these gamma/delta T cells may differentiate extrathymically in the liver.

Repertoire development and ligand specificity of murine TCR gamma delta cells

During the past several years, we have been studying the circulating TCR gamma delta cells expressed in peripheral lymphoid tissues. Biochemical and molecular characterization of the TCR gamma delta heterodimers present on these TCR gamma delta cells identified 3 TCR gamma proteins, V gamma 2-C gamma 1, V gamma 1.2-C gamma 2, and V gamma 1.1-C gamma 4. In addition, at least 6 different V delta gene products (V delta 2,4,5,6,V alpha 10, V alpha 11) are expressed in peripheral lymphoid tissue. Nucleotide sequence analysis has revealed a great deal of junctional diversity present among the different V gamma and V delta proteins. Thus, compared to other nonlymphoid tissues (e.g., skin), this population of TCR gamma delta cells appears quite extensive. The development and specificity of TCR gamma delta cells has been pursued by two approaches. First, different TCR gamma delta cells clones were generated which recognize MHC-encoded gene products. One clone recognizes an unconventional TL-encoded antigen, whereas others have been shown to recognize either classical MHC class I or class II antigens. The TCR gamma delta receptor genes have been cloned from the TL-specific TCR gamma delta cell and used to construct transgenic mice to examine the development of TCR gamma delta cells. Although the Tg+ TCR gamma delta cells are tolerized by thymic clonal tolerance similar to TCR alpha beta cells, the epithelial Tg+ TCR gamma delta cells are subjected to non-deletional tolerance (anergy). A second approach towards examining the development of TCR gamma delta cells has been to compare the repertoire of TCR gamma delta splenocytes in a variety of inbred and MHC-congenic strains of mice using subset-specific anti-murine TCR gamma delta mAb. The percentage of individual subsets of splenic TCR gamma delta cells differ widely between different inbred strains of mice due to both MHC- and TCR-encoded genetic differences. In summary, these studies provides a basis for understanding and determining the ligand(s) of the TCR gamma delta heterodimer and the factors which shape the peripheral TCR gamma delta repertoire.

A major fraction of human intraepithelial lymphocytes simultaneously expresses the gamma/delta T cell receptor, the CD8 accessory molecule and preferentially uses the V delta 1 gene segment

The frequency of T cell receptor (TcR) type and the variable gene segment expression in human intraepithelial lymphocytes (IEL) from the large intestinal mucosa were studied by flow cytometry and immunohistochemistry, and compared to those in peripheral blood lymphocytes (PBL) - or lamina propria lymphocytes (LPL). Employing anti-gamma/delta TcR and anti-alpha/beta TcR monoclonal antibodies (mAb), flow cytometric analysis revealed that a large fraction of IEL (37%) are gamma/delta T cells, whereas within LPL and PBL gamma/delta T cells comprise a minor population (4.6% and 3.8% respectively). At these sites the number of gamma/delta T cells labeled with anti-CD8 mAb were 58.3% (IEL), 43.3% (LPL) and 24.4% (PBL). In situ staining of serial sections of large intestine confirmed these results. Hence, these data suggest a selective accumulation of CD8+ gamma/delta T cells in the human epithelium of the large intestine. Furthermore, analysis of gamma/delta TcR bearing IEL+ disclosed a marked preponderance of cells using the V delta 1 gene segment, whereas gamma/delta TcR+ PBL preferentially express V delta 2. Strikingly, the majority of these V delta 1+ IEL bear the CD8 molecule on their surface. These results are taken as evidence for a selective localization of V delta 1+ CD8+ gamma/delta T cells in the epithelium of the large intestine.

Coding joint formation of endogenous T cell receptor genes in lymphoid cells from scid mice: unusual P-nucleotide additions in VJ-coding joints

The mouse mutation scid adversely affects the process of VDJ recombination. Attempts to form coding joints, that is, to joint V or D to J gene segments generally fail in developing scid lymphocytes. It has been proposed that the scid mutation results a defective VDJ recombinase system. Here we describe five scid T cell lymphomas containing one or two TcR gamma coding joints each, even though the majority of the multiple TcR gamma chain gene rearrangements and all TcR beta rearrangements in these cells were abnormal with the deletions typically found in scid lymphoid cells. One of the five T cell lymphomas was shown to have an active VDJ recombinase system; however, this activity was defective indicating that the scid phenotype has been retained. We conclude that the scid VDJ recombinase system has not completely lost the ability to form coding joints. P-nucleotide additions of unusual length or composition were found at the junctional border in five of the eight TcR gamma coding joints. This might reflect a defect in the activity of a component of the VDJ recombinase system involved in the generation of P-nucleotide additions. In one of the observed rearrangements, a V gamma 5-J gamma 3 coding joint was formed. This establishes the transcriptional orientation of J gamma 3-C gamma 3 and confirms a previously proposed organization of the TcR gamma genes.

Unusual phenotype of intestinal intraepithelial lymphocytes in the rat: predominance of T cell receptor alpha/beta+/CD2- cells and high expression of the RT6 alloantigen

The phenotype of intraepithelial lymphocytes (IEL) from the small intestine of adult rats was studied by flow cytometry. Using appropriate monoclonal antibodies the expression patterns of the T cell receptor alpha/beta (TcR2), CD2, the alloantigen RT6 and several other T cell antigens were analyzed. The vast majority of rat IEL expressed TcR2 which is in contrast with data reported for the mouse. The comparison of IEL with lymph node cells revealed major phenotypic differences. Whereas CD2 was present on virtually all lymph node T cells it was found on only less than 5% of IEL. The T cell-specific differentiation antigen RT6 present on only a fraction of lymph node cells was found on about 99% of IEL demonstrating uniform expression with an approximately tenfold higher density. Identity of the detected molecule with RT6 was proven by using congenic controls and by the demonstration of phosphatidylinositol linkage to the IEL membrane. About 86% of IEL expressed CD8 but a substantial proportion of these cells co-expressed the CD4 molecule (34%). Two-color analysis revealed that the CD4+CD8+ double-positive subset completely lacked CD45RB suggesting that they represent memory cells. In the CD4-CD8+TcR2+ subset there was a remarkable heterogeneity of CD5 expression. A substantial number of these cells did not express CD5 despite high density of TcR2. Phenotypic peculiarities found on all or most IEL such as the lack of CD2 and the increased expression of RT6 indicate that the intestinal epithelial environment exerts strong effects on the development and maturation of these cells.

Dominant expression of the T cell receptor BALB invariant delta (BID) chain in resident pulmonary lymphocytes is due to selection

During ontogeny, the T cell receptor BALB invariant delta (BID) chain (Sim, G. -K. and Augustin, A., Cell 1990. 61:397) is generated in C57BL/6 fetal thymocytes at levels similar to those detected in BALB/c mice. Hence, the dominance of BID observed among resident pulmonary lymphocytes of BALB/c and of (BALB/c x C57BL/6) F1 and its absence in C57BL/6 mice is due to positive selection and peripheral expansion rather than to the inability of C57BL/6 mice to generate this particular rearrangement.

Two gut intraepithelial CD8+ lymphocyte populations with different T cell receptors: a role for the gut epithelium in T cell differentiation

Mouse gut intraepithelial lymphocytes (IEL) consist mainly (90%) of two populations of CD8+ T cells. One bears heterodimeric alpha/beta CD8 chains (Lyt-2+, Lyt-3+), a T cell receptor (TCR) made of alpha/beta chains, and is Thy-1+; it represents the progeny of T blasts elicited in Peyer's patches by antigenic stimulation. The other bears homodimeric alpha/alpha CD8+ chains, contains no beta chain mRNA, and is mostly Thy-1- and TCR-gamma/delta + or -alpha/beta +; it is thymo-independent and does not require antigenic stimulation, as shown by its presence: (a) in nude and scid mice; (b) in irradiated and thymectomized mice repopulated by T-depleted bone marrow cells bearing an identifiable marker; (c) in thymectomized mice treated by injections of monoclonal anti-CD8 antibody, which lead to total depletion of peripheral CD8+ T lymphocytes; and (d) in germ-free mice and in suckling mice. In young nude mice, alpha/alpha CD8 chains, CD3-TCR complexes, and TCR mRNAs (first gamma/delta) are found on IEL, while they are not detectable on or in peripheral or circulating lymphocytes or bone marrow cells. IEL, in contrast to mature T cells, contain mRNA for the RAG protein, which is required for the rearrangement of TCR and Ig genes. We propose that the gut epithelium (an endoderm derivative, as the thymic epithelium) has an inductive property, attracting progenitors of bone marrow origin, and triggering their TCR rearrangement and alpha/alpha CD8 chains expression, thus giving rise to a T cell population that appears to belong to the same lineage as gamma/delta thymocytes and to recognize an antigenic repertoire different from that of alpha/beta CD8+ IEL.

Prominence of gamma delta T cells in the ruminant immune system

The lymphoid systems of sheep and cattle contain a large number of gamma delta T cells, in striking contrast to the lymphoid systems of humans and mice. In neonatal animals particularly, these cells comprise the predominant fraction of T cells in the blood. Here Wayne Hein and Charles Mackay discuss what is currently known about the ontogeny, phenotype, tissue distribution and function of gamma delta T cells in ruminants. There are a number of interesting molecular features that characterize ruminant gamma delta T cells, but these do not entirely explain the high frequency of use of the gamma delta T-cell receptor in these animals. Studies on sheep, cattle or other animals that preferentially use gamma delta T cells should provide insights into the biological significance of the existence of two distinct forms of the T-cell receptor.

Regulated expression and structure of T cell receptor gamma/delta transcripts in human thymic ontogeny

Gamma delta (gamma delta) T cells have been found in all vertebrates examined, yet their function in vivo remains unknown. Because gamma delta T cell receptors are related to immunoglobulin, and because they are encoded by rearranging, multi-gene families, the receptors are thought to be antigen recognition molecules. However, a capacity to recognize naturally diverse antigens has not yet been shown. In this work, the expression and structure of human gamma delta transcripts have been examined in the fetal and early post-natal thymus. The data indicate that many gamma and delta genes are rearranged and expressed throughout ontogeny, but that as ontogeny proceeds, quite dramatic changes occur in the patterns of gene expression and rearrangement. In particular, receptors encoded by early to mid-gestation fetal thymic transcripts would be of quite restricted diversity. Only later in ontogeny can receptors of substantial diversity be generated. These properties are very similar to the patterns of gamma delta gene activation in the mouse, and they serve to reiterate similarities both in gene rearrangement and in gamma delta across vertebrate species.

Extrathymic origin of intestinal intraepithelial lymphocytes bearing T-cell antigen receptor gamma delta

The kinetics of postnatal intestinal colonization by T cells carrying gamma delta and alpha beta T-cell antigen receptors were studied in nude and normal mice by flow cytometry and immunohistology. Furthermore, gamma delta and alpha beta T-cell development was analyzed in lethally irradiated mice that were reconstituted by fetal liver precursors with or without a thymus. Our results establish that a major subpopulation of gamma delta intestinal intraepithelial lymphocytes is produced from uncommitted precursors at extrathymic sites. This work further shows that a small pool of T cells carrying alpha beta T-cell receptors can also differentiate extrathymically from CD3- fetal liver precursors but with rates of production and peripheral expansion much reduced as compared with those observed in thymus-bearing animals.

The neonatally T cell receptor 2-suppressed rat: lymphocyte subset composition and immune reactivity

Rats were injected intraperitoneally from birth on with a mouse monoclonal antibody (R73) to a constant determinant of the rat T cell receptor (TcR)2. Throughout the observation period (6 months), TcR2+ cells in peripheral lymphoid organs and blood were absent in treated animals with the exception of few (less than 10%) cells with a tenfold reduced TcR2 density; peripheral TcR2-CD3+ cells, i.e. most likely TcR1+ T cells, were increased in frequency. Among thymocyte subpopulations, only those expressing the TcR2 at a high level were reduced in number. The lack of a visible effect on immature thymocytes may, however, be due to the fact that despite high serum levels, thymic R73 determinants were incompletely saturated. Spleen and lymph node cells from TcR2-suppressed rats were completely unresponsive in mixed lymphocyte reaction (two fully allogeneic haplotypes tested) even in the presence of interleukin 2. Reactivity to the T cell mitogen concanavalin A was, in contrast, only partially reduced. Since rat TcR1 cells are activated by concanavalin A, these results suggest that the TcR1 cells present in TcR2-suppressed rats are functional, but do not respond to foreign major histocompatibility complex antigens at a high frequency, a finding of possible importance for immunosuppression with anti-TcR2 monoclonal antibody in human allografting. Neonatally TcR2-suppressed rats were unable to respond to the strong T-dependent antigen keyhole limpet hemocyanin administered intraperitoneally in alum with B. pertussis. Thus, in the absence of peripheral TcR2 cells, the numerically expanded TcR1 T cells are not capable of providing help for B lymphocytes.

T gamma delta cells and their subsets in blood and synovial tissue from rheumatoid arthritis patients

We have examined the frequencies of T gamma delta cells in blood, synovial fluids, and synovial membranes of patients with rheumatoid arthritis (RA) and in blood from age-matched controls. Immunocytochemical and immunohistochemical techniques were used with monoclonal antibodies BB3 and A13 to define a major and minor blood subset of T gamma delta cells respectively. Together, these antibodies identify the majority (if not all) of the peripheral blood T gamma delta cells. Significantly lower levels of T gamma delta cells were found in the blood of RA patients compared with controls, whilst higher but not significant numbers were found in the synovial fluids of paired samples. Scattered T gamma delta cells were found only in some synovial membranes with a distribution similar to the T alpha beta cells. Analysis of the two different T gamma delta-cell subsets indicated a ratio of BB3 to A13 of about 5:1 in control and RA blood. However, this ratio was less than 1:1 in the RA synovial fluids and membranes. The migratory nature of the A13+ cells could account for their predominance in these sites. The possible pathological significance of these cells in the rheumatoid synovial fluid and synovial membranes is discussed.