Phenotype, activation and lymphokine secretion by gamma/delta T lymphocytes from schistosomiasis and carcinoma of the urinary bladder.

In humans the majority of the CD3+ T cells usually express an alpha/beta T cell receptor (TcR) and a minority express a gamma/delta TcR. The CD3+ TcR alpha/beta and CD3+ TcR gamma/delta cells from blood of the patients with schistosomiasis with carcinoma of the urinary bladder (SCB) were analyzed for phenotype, activation, secretion of interleukin 2 (IL 2). B cell growth factor (BCGF) and B cell differentiation factor (BCDF), as well as for autologous (AMLR) and allogeneic (MLR) mixed lymphocyte reaction. Patients with SCB had a highly increased percentage of CD3+ TcR gamma/delta and a decreased percentage of CD3+ TcR alpha/beta T cells in their circulation. These CD3+ TcR gamma/delta T cells expressed the CD25 (IL 2 receptor), CD38, CD71 (transferrin receptor) and HLA-DR activation antigens at a higher intensity after in vitro stimulation with recombinant IL 2, phytohemagglutinin and soluble egg antigen (from Schistosoma haematobium). The SCB patients' CD3+ TcR gamma/delta T cells were highly deficient in secretion of IL 2 but produced highly elevated levels of BCGF and BCDF. On the contrary, both BCGF and BCDF activities of the CD3+ TcR alpha/beta T cells were decreased. Moreover, CD3+ TcR gamma/delta T cells demonstrated highly deficient AMLR and MLR activity. These observations suggest a possible role of CD3+ TcR gamma/delta T cells in the immune response and the disease pathogenesis in human schistosomiasis infections.     

Gamma delta T cells and the immune response in visceral leishmaniasis.

Visceral leishmaniasis (VL) caused by Leishmania donovani, a protozoan parasite, is a disease of high morbidity associated with hepatosplenomegaly, hypergammaglobulinemia, fever and death. One of the immunological hallmarks of VL is a remarkable increase in serum immunoglobulin levels as a result of polyclonal B cell activation. This study demonstrated that T lymphocytes expressing the T cell receptors (TcR) gamma delta in association with CD3 molecules are increased in circulation of patients with VL. A large proportions of TcR gamma delta-bearing T cells had CD4+ CD8- phenotype, and expressed CD25, CD38, CD71 and HLA-DR activation antigens. Furthermore, we demonstrated wide functional differences in TcR gamma delta and TcR alpha beta T cells in their proliferative response, secretion of interleukin-2 (IL-2), B cell growth factor (BCGF) and B cell differentiation factor (BCDF). It was of interest that the TcR gamma delta T cells from patients with VL could be expanded by in vitro culture with human recombinant IL-2. Although these TcR gamma delta T cells secreted diminished levels of IL-2, they produced highly augmented levels of both BCGF and BCDF, suggesting that secretion of these lymphokines in these T cell subsets is regulated independently. The relative increases in the CD4+ CDw29+ TcR gamma delta T cell subsets and their secretion of highly elevated levels of BCGF and BCDF largely accounted for the humoral immune system abnormality and hypergammaglobulinemia found in this disease. These observations may help to explain that TcR gamma delta T cells might be functional in vivo and are involved in immunological mechanisms of pathogenesis in VL.     

Detection, Isolation and Functional Studies of CD25+ T Cells in Lymph Nodes Involved by B-Cell Non-Hodgkin''s Lymphomas

We searched for the presence of IL2 receptor (CD25) on T cells as an activation marker in lymph nodes involved by B-cell non-Hodgkin's lymphomas (B-NHL). In 26 malignant lymph nodes studied, the number of CD25+ T cells among total T cells was usually low when assessed by immunofluorescence analysis (mean +/- SD: 6.7% +/- 11.2%), but greatly increased when an immunomagnetic rosette method was used (mean +/- SD: 17.5% +/- 16.6%). In six cases, CD25-/CD25/CD25+ cells were isolated by immunomagnetic separation, with a purity greater than 97% for both populations. Expansion of CD25-/CD25+ T cells was obtained with IL2 and PHA, then conditioned media (CM) were prepared. No IL2 activity was found in CM from both CD25-/CD25+ T cells when tested on CTLL2 cells. BCGF and BCDF mu/gamma activities were assayed on normal B cells stimulated with soluble or insolubilized anti-mu antibodies(BCGF) or with Cowan I (BCDF). Results of production of all these activities were comparable for both populations, and thus do not favour the possibility that CD25+ T cells closely associated with malignant B-NHL cells in lymph nodes may influence their proliferation (BCGF) or expression/secretion of heavy chain isotype (BCDF mu/gamma).     

Differential expression and regulation of the human CD8α and CD8β chains

The CD8 glycoprotein is expressed by thymocytes, mature T cells and natural killer (NK) cells and has been implicated in the recognition of monomorphic determinants on major histocompatibility complex (MHC) Class I antigens, and in signal transduction during the course of T-cell activation. Both human and rodent CD8 antigens are comprised of two distinct polypeptide chains, alpha and beta. The majority of monoclonal antibodies (mAb) reactive with the human CD8 antigen bind the CD8 alpha chain, while a single mAb, T8/2T8-5H7, has been identified which binds to the CD8 alpha/beta heterodimer. While the two chains of CD8 have been presumed to be coordinately expressed in normal T cells, this is not always the case. Northern blot analysis of a panel of T-cell leukemias and normal cells demonstrate that CD8 alpha and CD8 beta are not invariably co-transcribed and phenotypic analysis of fresh and interleukin 2 (IL-2) expanded peripheral blood mononuclear cells (PBMC) confirm that the CD8 alpha and CD8 beta chains are differentially expressed at the cell surface. Four distinct subpopulations of CD8+ cells have been identified based on the expression of CD8 alpha/alpha or CD8 alpha/beta complexes: (1) T-cell receptor (TcR) alpha beta+ T cells which are CD8 alpha+/beta+; (2) TcR alpha beta+ T cells which are CD8 alpha+/beta-; (3) TcR gamma delta+ T cells which are CD8 alpha+/beta- and (4) natural killer (NK) cells which are CD8 alpha+/beta-. We also demonstrate the down-regulation of the CD8 alpha/beta heterodimers from the surface of a CD8+ T-cell clone following treatment with phorbol myristate acetate (PMA) while CD8 alpha/alpha homodimers remain on the cell surface. This observation demonstrates that a) a CD8+ T-cell clone can express both CD8 alpha/alpha homodimers and CD8 alpha/beta heterodimers and b) these two complexes do not have identical biological properties. Together, these data suggest that CD8 alpha/alpha and CD8 alpha/beta dimers may not subserve identical functions. The differential contribution of these two CD8 complexes should be considered in models of T-cell-mediated cytotoxicity and T-cell activation.     

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.     

Autoreactive T cell hybridoma-derived B cell stimulatory factor(s) governing IgA isotype immunoglobulin production by murine Peyer's patch B cells

In the present study we investigated whether autoreactive T cells derived from murine Peyer's patches (PP) have the capacity to regulate mucosal B cell differentiation to IgA-producing plasma cells in vitro. We also examined whether B cell development is mediated by lymphokines from immunoregulatory T cells - that is, B cell stimulatory factors (BSF) and cofactors (coBSF) - which include B cell growth factor (BCGF), putative alpha B cell immunoglobulin (Ig) heavy chain switch factor (BSWF alpha), and B cell differentiation factor (BCDF), as well as interleukin-2 (IL-2). To this purpose we developed in vitro a variety of BSF (especially putative BSWF alpha)-producing autoreactive (self-class II molecules responsive) T cell hybridoma cell clones from murine PP, and studied the functional activity of the BSF, especially a putative alpha Ig heavy chain switch (mu----alpha) factors(s). These T hybridome cell lines possessed the surface phenotypes of Thy 1.2, CD4+, CD5+ and CD8- and produced a variety of BSF, including two kinds of BCGF (IL-5, and a BCGF that did not require additional costimulators to induce proliferation of preactivated B cells), putative BSWF alpha/gamma, BCDF, and/or IL-2. The results strongly support the view that the autologous T cell plays an important role not only in B cell proliferation and terminal maturation, but also in alpha heavy chain switching in PP. This T-B cell interation is mediated at least in part through BSF lymphokines elaborated by the autoreactive T cell, probably activated in situ in the lymphoid tissue microenvironment.     

Influence of beta 2-microglobulin expression on gamma interferon secretion and target cell lysis by intraepithelial lymphocytes during intestinal Listeria monocytogenes infection.

Numerous microbial pathogens, including Listeria monocytogenes, enter the host through the intestine. Although relatively little is known about the biological functions of intestinal intraepithelial lymphocytes (i-IEL), they are generally considered a first line of defense against intestinal infections. In the mouse, the vast majority of i-IEL express the CD8 coreceptor either as a CD8 alpha/alpha homodimer or as a CD8 alpha/beta heterodimer. The CD8 receptor of T-cell receptor TcR gamma/delta i-IEL is exclusively homodimeric, whereas the CD8-expressing TcR alpha/beta i-IEL segregate into equal fractions of CD8 alpha/alpha and CD8 alpha/beta cells. We infected beta 2-microglobulin (beta 2m)+/- mice (possessing all i-IEL populations) and beta 2m -/- mutant mice (lacking all CD8 alpha/beta + i-IEL and having few CD8 alpha/alpha + TcR alpha/beta i-IEL) with L. monocytogenes per os and determined their biological functions after TcR ligation with monoclonal antibodies. Cytolytic activities of TcR alpha/beta and TcR gamma/delta i-IEL from beta 2m +/- mice were not influenced by intestinal listeriosis. Cytolytic activities of TcR alpha/beta i-IEL were impaired in uninfected beta 2m -/- mice, but this reduction was reestablished as a consequence of intestinal listeriosis. Frequencies of gamma interferon (IFN-gamma)-producing TcR alpha/beta i-IEL in uninfected beta 2m -/- mice were reduced, compared with that in their heterozygous controls. Equally low frequencies of IFN-gamma-producing TcR gamma/delta i-IEL in beta 2M +/- and beta 2m-/- mutants were found. Listeriosis increased frequencies of INF-gamma-producing TcR alpha/beta and TcR gamma/delta i-IEL in both mouse strains. Most remarkably, the proportion of IFN-gamma-producing TcR gamma/delta i-IEL was elevated 10-fold in listeria-infected beta 2M -/- mice. Our findings show that the beta 2m-independent CD8 beta- i-IEL expressing either TcR alpha/beta or TcR gamma/delta are stimulated by intestinal listeriosis independent of regional beta 2m expression. We conclude that the three major CD8+ i-IEL populations are stimulated by intestinal listeriosis and that CD8 beta- i-IEL compensate for the total lack of CD8 beta+ i-IEL in beta 2M -/- mutant mice. Hence, in contrast to the peripheral immune system, which crucially depends on CD8 alpha/beta + TcR alpha/beta lymphocytes, the mucosal immune system can rely on additional lymphocytes expressing the CD8 alpha/alpha homodimer.     

Identification and characterization of rat T cell subpopulations expressing T cell receptors alpha/beta and gamma/delta

Peripheral lymphoid organs of the rat were investigated for the presence of lymphocytes that expressed the pan-T cell markers CD5 and OX-52 but not the T cell receptor (TcR) alpha/beta. Two such populations were identified: 2% to 4% of lymphocytes in adult spleen, lymph nodes and peripheral blood are CD5+ TcR alpha/beta- and express the OX-52 antigen at the same density as TcR alpha/beta+ T-cells. About 90% of these cells are CD8+. A second population is CD5-, CD8+ and OX-52low. Radioimmunoprecipitation from digitonin lysates of surface-labeled cells with an anti-CD3 antiserum showed that the CD5+, but not the CD5- population of TcR alpha/beta- cells expresses a CD3-associated disulfide-linked cell surface molecule of about 100 kDa apparent mol. mass. Upon reduction, one major band, migrating with 48 kDa was observed. A band of the same size was obtained with an anti-human delta chain peptide antiserum, indicating that the CD3-associated non-TcR alpha/beta molecule is the rat TcR gamma/delta. Functional assays showed that most, if not all natural killer (NK) cell activity is present in the CD5(-)-OX-52low population. Reactivity to foreign major histocompatibility complex (MHC) antigens in mixed lymphocyte reaction was exclusively found in TcR alpha/beta+ splenic T cells. It is concluded that rat gamma/delta T cells in the spleen do not contain a high frequency of cells with specificity for foreign MHC antigens. The seeding of the periphery with alpha/beta and the presumptive gamma/delta T cells was followed from birth. Most prominently in the spleen, alpha/beta T cells reached adult levels much later than gamma/delta T cells. Taken together, these findings demonstrate the expression of the TcR gamma/delta on a minor population of peripheral rat T cells with the predominant phenotype CD4-CD8+ that has no NK cell activity when freshly isolated and does not contain a high frequency of alloreactive cells.     

Membranes of activated CD4+ T cells expressing T cell receptor (TcR) alpha beta or TcR gamma delta induce IgE synthesis by human B cells in the presence of interleukin-4.

In the present study it is demonstrated that human B cells can be induced to switch to IgE production following a contact-mediated signal provided by activated T cell receptor (TcR) gamma delta+, CD4+ and TcR alpha beta+, CD4+ T cell clones and interleukin (IL)-4. The signal provided by these T cell clones was antigen nonspecific, indicating that the TcR alpha beta/CD3 or TcR gamma delta/CD3 complexes were not involved in these T-B cell interactions. Activated TcR alpha beta+, CD8+, and TcR gamma delta+, CD4-CD8-, or resting CD4+ T cell clones were ineffective. Intact TcR alpha beta+ or TcR gamma delta+, CD4+ T cell clones could be replaced by plasma membrane-enriched fractions isolated from these activated CD4+ T cell clones. In contrast, membranes isolated from resting TcR alpha beta+, CD4+, TcR gamma delta+, CD4+ T cell clones or an Epstein-Barr virus (EBV)-transformed B cell line (EBV-LCL) failed to provide the costimulatory signal that, in addition to IL-4, is required for induction of IgE synthesis. As described for intact CD4+ T cells, CD4+ T cell membranes induced purified surface IgM+ B cells to switch to IgG4- and IgE- but not to IgA-producing cells, excluding the possibility of a preferential outgrowth of IgG4- and IgE-committed B cells. The membrane activity was inhibited by protease or heat treatment. Induction of IgE synthesis by B cells co-cultured with both TcR alpha beta+, CD4+ and TcR gamma delta+, CD4+ T cell clones and membrane preparations of these cells was blocked by anti-class II major histocompatibility complex (MHC) monoclonal antibodies (mAb), whereas various anti-CD4 mAb had differential blocking effects. Murine L cells, or EBV-LCL transfected with CD4 could not replace CD4+ T cell clones. These results indicate that, although CD4 and class II MHC antigens are required for productive CD4+ T cell clone-B cell interactions, an additional signal, provided by a membrane associated (glyco)protein that is induced by activation of both TcR alpha beta and TcR gamma delta, CD4+ T cells, is needed for induction of IgE production in the presence of IL-4.     

Effects of cyclosporin A on T-cell development in organ-cultured foetal thymus.

The effects of cyclosporin A (CsA) on T-cell development were assessed in an organ culture of murine foetal thymus. Applying three-colour flow cytometric analysis, we showed that the agent inhibits the development of mature CD3/T-cell receptor alpha beta (TcR alpha beta)+ cells both in CD4+8- and CD4-8+ populations. CD4-8- cells appeared to be accumulated by CsA. We examined the heterogeneity of CD4-8- cells generated in the organ culture, and defined five subpopulations by the expression of the cell-surface molecules CD3/TcR, J11d and CD25. It has been demonstrated that only the CD3/TcR alpha beta+ J11d- CD25- subpopulation is susceptible to the suppressive effects of CsA among CD4-8- cells, whereas all the other four subpopulations, including CD3/TcR gamma delta+ cells, are resistant. Thus, all of the TcR alpha beta-bearing cells, including CD4-8- cells but none of the TcR alpha beta- cells, are CsA sensitive. Because it is known that CsA inhibits the TcR-mediated signalling events in mature T cells and that signallings mediated via the interaction of TcR with major histocompatibility complex (MHC) molecules on thymic stroma cells are crucial for thymic selection of T cells, these results indicate that TcR alpha beta-bearing CD4-8- cells but not TcR gamma delta-bearing CD4-8- cells undergo thymic positive selection.     

Phenotypic heterogeneity of intraepithelial T lymphocytes from mouse small intestine.

We have used two-colour flow cytometry to examine the heterogeneity of intraepithelial lymphocytes (IEL) from mouse small intestine. We have confirmed the predominance of CD3+ Thy 1- CD8+ IEL and show that a substantial but variable proportion of CD8+ IEL does not express the alpha beta T-cell receptor (TcR) for antigen. Simultaneous analysis of the co-expression of the alpha and beta chains of the CD8 heterodimer and of the alpha beta TcR revealed three populations of CD8+IEL. The first of these expressed both CD8 alpha and beta chains and had normal expression of V beta families and so represented conventional CD8+ alpha beta TcR+ T cells. The second population comprised alpha beta TcR- T cells (presumed gamma delta TcR+) which expressed only the alpha chain of the CD8 molecule. Finally, we identified a second, unique population of alpha beta TcR+ CD8+ IEL which were also CD8 beta-. Gamma delta + IEL predominated in mice aged less than 8 weeks, but there was a rapid increase in both populations of alpha beta TcR+ CD8+ IEL in older mice. CD8+ IEL were similar to peripheral CD8+ T cells in having high expression of the CD45RB molecule, but CD4+ IEL had generally lower expression of CD45RB than their peripheral counterparts, despite having normal expression of TcR. These findings emphasize the heterogeneity of IEL and underline the need to study phenotypically defined populations.     

Abnormal Production of and Response to B-Cell Growth Factor and B-Cell Differentiation Factor in Patients with Systemic Lupus Erythematosus

We examined the production of and the response to B-cell growth factor (BCGF) and B-cell differentiation factor (BCDF) in 21 patients with systemic lupus erythematosus (SLE) and 23 normal subjects. T cells, 2.5 × 10⁶/ml, were cultured for 24 or 72 h with 1% phytohaemagglutinin (PHA). After absorption of PHA by chicken erythrocytes (CRBC), they were used for BCGF and BCDF. In inactive SLE, BCGF activity was significantly lower than that in normal subjects. Active SLE contained two separate groups, one showing normal BCGF activity and the other showing lower activity than normal. In contrast. BCDF activity from initial culture in active SLE was elevated. The B-cell response both to BCGF and BCDF was elevated in active SLE without Staphylococcus aureus Cowan I antigen (SAC) preactivation. However, the B-cell response to SAC was markedly disturbed. Thus SLE B cells were shifted to the mature state in vivo. We also demonstrated pivotal abnormalities of monocytes in SLE B-cell growth and differentiation. These results may contribute to the understanding of the abormalities of T-B interactions and the overproduction of antibody in SLE.     

Cytotoxic alpha/beta+ and gamma/delta+ T cells in murine intestinal epithelium

Murine intraepithelial lymphocytes (IEL) consist of two main populations. Approximately half are Thy-1+, most of which are CD3+, T cell receptor (TcR) alpha/beta+, and the remainder are Thy-1-, most of which are CD3+, TcR alpha/beta- (presumably TcR gamma/delta+). In redirected cytotoxicity assays, TcR alpha/beta+ IEL are potent cytotoxic effectors. Thy-1-, CD3+, TcR alpha/beta- IEL isolated from athymic mice are also cytotoxic. Thus, regardless of TcR usage or Thy-1 expression, IEL are cytotoxic effectors.     

Autorective T Cell Hybridoma-Derived B Cell Stimulatory Factor(s) Governing IgA Isotype Immunoglobulin Production by Murine Peyer's Patch B Cells

In the present study we investigated whether autoreactive T cells derived from murine Peyer's patches (PP) have the capacity to regulate mucosal B cell differentiation to IgA-producing plasma cells in vitro. We also examined whether B cell development is mediated by lymphokines from immunoregulatory T cells – that is, B cell stimulatory factors (BSF) and cofactors (coBSF) – which include B cell growth factor (BCGF), putative alpha B cell immunoglobulin (Ig) heavy chain switch factor (BSWF alpha), and B cell differentition factor (BCDF), as well as interleukin-2 (IL-2).

To this purpose we developed in vitro a variety of BSF (especially putative BSWF alpha)-producing autoreactive (self-class II molecules responsive) T cell hybridoma cell clones from murine PP, and studied the functional activity of the BSF, especially a putative alpha Ig heavy chain switch (μ + α) factors(s). These T hybridome cell lines possessed the surface phenotypes of Thy 1.2, CD4+, CD5+ and CD8- and produced a variety of BSF, including two kinds of BCGF (IL-5, and a BCGF that did not require additional costimulators to induce proliferation of preactivated B cells), putative BSWF alpha/gamma, BCDF, and/or IL-2. The results strongly support the view that the autologous T cell plays an important role not only in B cell proliferation and terminal maturation, but also in alpha heavy chain switching in PP.

This T-B cell interation is mediated at least in part through BSF lymphokines elaborated by the autoreactive T cell, probably activated in situ in the lymphoid tissue microenvironment.     

T-cell receptor-bearing cells from athymic nude rats respond to alloantigen in vitro but are defective in vivo.

T-like cells from congenitally athymic nude rats of the PVG (RT1c) strain were characterized both phenotypically and functionally. There was an age-dependent increase in the number of alpha beta TcR+CD3+ cells in the lymph nodes, spleen and thoracic duct of nude rats. These cells, which comprised up to 25% of lymph node cells in animals of 8-12 months in age, were also CD3+CD5+Thy-1.1-. The expression of CD4 and CD8 on T-like cells was mutually exclusive. Approximately 30% of the CD4+ cells expressed CD45RB and 50% of the TcR+ cells expressed RT6. B-cell-depleted TcR+ cells from nude animals gave proliferative responses to mitogenic lectins or immobilized anti-CD3 antibody. T-like cells showed comparable alloreactivity to their euthymic counterparts in mixed lymphocyte reactions (MLR) against three different MHC haplotypes and to lymphocytes of a congenic strain differing only in MHC-encoded products. Monoclonal antibodies (mAb) to CD4, MHC class II, alpha beta TcR and CD3 blocked the MLR. However, T-like cells failed to induce rejection of skin allografts of the same MHC haplotypes when adoptively transferred to athymic nude hosts and were unable to mount a normal graft-versus-host (GVH) response. These results indicate that lymphocytes may rearrange and express a functional TcR in the absence of a thymus, but that the thymic microenvironment is essential for T cells to acquire full in vivo function.     

T cell receptor-bearing cells among rat intestinal intraepithelial lymphocytes are mainly alpha/beta+ and are thymus dependent

Rearrangement of both the beta and gamma chain T cell receptor (TcR) genes was detected in intestinal intraepithelial lymphocytes (IEL) from normal euthymic rats. Flow cytometric analyses showed that about 73% of the IEL were CD3+ (1F4) and that 67% were TcR alpha/beta+ (R73). About 5% of the IEL were found to be CD3+, TcR alpha/beta- in double-labeling experiments suggesting that a small fraction of IEL in the rat express the alternative TcR gamma/delta. More than 70% of the IEL were granular implying that many CD3+ IEL are granular. In IEL from athymic nude rats no rearrangement of either the TcR beta or gamma chain genes or surface expression of CD3 or TcR alpha/beta was detected despite the fact that about 95% of the cells were granular and morphologically similar to those in normal rats. Taken together our data suggest that the majority of IEL in the rat express the conventional TcR alpha/beta and that TcR-bearing cells in the gut epithelium are thymus dependent.     

Severe T lymphocyte immunodeficiency associated with hypogammaglobulinemia: Defective lymphokine secretion but enhanced autologous mixed lymphocyte reaction

The multiparameter immunologic study of T cells of a patient with acquired hypogammaglobulinemia was investigated, since he had a normal B-cell number and function. His peripheral blood lymphocytes were found to contain predominant CD4+ CD45R+ T cells with a clear deficiency of CD4+ CDw29+ as well as CD8+ T cells. His T cells proliferated in response to phytohemagglutinin (PHA) and pokeweed mitogen (PWM), but no immunoglobulin was secreted in PWM-induced patient's T-cell and normal B-cell differentiations. His T cells were also found to posses concanavalin A (Con A)-induced suppressor function when cocultured with normal T cells, as well as IgG-, IgA-, and IgM-specific suppressor function on PWM-induced normal T- and B-cell differentiations. The patient's T cells were found to secrete elevated amounts of interleukin-2 but failed to secrete two important B-cell stimulating factors, B-cell growth factor and B-cell differentiation factor, in response to PHA. An investigation of immunoregulatory T-cell function in the autologous mixed lymphocyte reaction (AMLR) and allogeneic mixed lymphocyte reaction (MLR) indicated that the patient's T cells produced an enhanced AMLR but were deficient in MLR. These results suggest that the abnormalities we have identified in this patient with hypogammaglobulinemia reflect an intrinsic defect of T cells in the humoral immune response to produce three major immunoglobulins.     

Presence of CD8 alpha-CD8 beta-positive TcR gamma/delta thymocytes in the fetal murine thymus and their in vitro expansion with interleukin-7.

Several groups have described that a low percentage of in vitro cultured T cell receptor (TcR) gamma/delta cells express CD8. Contrary to TcR alpha/beta cells, however, CD8 on these TcR gamma/delta cells was shown to be a CD8 alpha homodimer. We describe here that addition of interleukin-7 (IL-7) to a short-term in vitro culture of fetal day 14 thymic lobes in an organ culture system or of fetal day 18 fetal thymocytes in cell suspension yields CD8 beta-positive TcR gamma/delta cells. This is not the result of IL-7-induced expression of CD8 beta on previously CD8 beta-negative cells. It is due to IL-7-induced expansion of CD8 alpha-CD8 beta-positive TcR gamma/delta cells which are shown to be present in the starting fetal thymocyte cell population.     

Expression and role of interleukin-2 receptor beta chain on CD4-CD8- T cell receptor alpha beta+ cells [corrected]

Using anti-murine interleukin-2 receptor beta chain (IL-2R beta) monoclonal antibody (mAb), we have examined the expression of IL-2R beta on murine thymocyte subpopulations. We found that it was constitutively expressed on 1%-4% of thymocytes in an almost mutually exclusive fashion with IL-2R alpha. The expression of IL-2R beta is developmentally regulated. While it is expressed mainly on T cell receptor gamma delta+ (TcR gamma delta+) cells during fetal age, the major subpopulation expressing IL-2R beta in adult mouse shifts to CD4-CD8-TcR alpha beta+ thymocytes. A considerable portion of CD4-CD8- TcR alpha beta+ cells in other organs, including spleen, bone marrow and liver, was also found to express IL-2R beta. In fetal thymus organ culture, the above thymocyte subset was induced to expand in response to exogeneous IL-2, and the expansion was inhibited by addition of anti-IL-2R beta mAb, suggesting that IL-2R beta is functional in this subpopulation. However, in vivo blockade of the IL-2/IL-2R pathway with the mAb did not exert any effects on the appearance of CD4-CD8- TcR alpha beta+ cells both in the thymus and the periphery. This indicates that the development of CD4-CD8- TcR alpha beta+ cells is not solely controlled by IL-2 but also by other complex elements.