Intrathyroidal accumulation of T cell phenotypes in autoimmune thyroid disease.

In this study we have correlated peripheral T cell subset phenotypes with intrathyroidal lymphocyte accumulation in patients with autoimmune thyroid disease (Graves' and Hashimoto's disease). Our study utilized euthyroid family members for one of our control groups (n = 48) thus significantly limiting familial, but not disease-specific, influences on these T cell phenotypes. Our principal new observations were found only in patients with Graves' disease. As previously reported, there was a decrease in CD8+ (suppressor/cytotoxic) T cells in the peripheral blood of patients with untreated hyperthyroid Graves' disease (n = 27) (mean +/- SEM, 19 +/- 1.1% in patients compared with 25 +/- 1.2% in controls, p = 0.03), a finding not observed in treated, euthyroid Graves' disease patients or their relatives. However, the relative number of CD8+ T cells, assessed by CD4:CD8 ratios, was increased in the intrathyroidal T cell populations (n = 10), when compared to normal and patient peripheral blood. There were no consistent changes in total CD4+ (helper) T cells in the peripheral blood of patients with treated and untreated Graves' disease but a reduction in CD4+2H4+ (suppressor-inducer) T cells was seen in patients undergoing surgery for Graves' disease (13 +/- 6.9% compared with 39 +/- 3.4%). Again, however, this T cell subset was increased within the target organ of the same patients (41 +/- 5.9%). These data point to either a selective accumulation, or a specific "homing", of certain T cell subsets within the thyroid gland of patients with Graves' disease where T cell differentiation may be strongly influenced by antithyroid drug treatment and the local immune environment.     

Class II HLA-DR antigens on non-autoimmune human thyroid cells stimulate autologous T cells with high suppressor activity

Human autoimmune thyroid cells "spontaneously" express MHC-class II antigens. These antigens have been assumed to trigger thyroid-specific helper T cell clones, leading in turn to the expansion of thyroid autoantibody-secreting B cells. Thyroid cells derived from non-autoimmune subjects do not express MHC-class antigens, but these can be readily induced with gamma-interferon. We have addressed the issue of whether it is sufficient for normal thyroid cells to bear class II antigens in order to trigger autologous T cells. We found that non-autoimmune thyrocytes expressing DR antigens fail to stimulate autologous resting T cells. However, proliferative activity and interleukin-2 secretion were observed when fresh T cells were first triggered by autologous non-T cells and then incubated with thyrocytes. More CD8 than CD4 cells proliferated in the T:thyrocyte cultures, but CD4 cells were necessary for the proliferation and interleukin-2 secretion. Addition of antibodies to thyroglobulin or to DR antigens inhibited T cell proliferation and interleukin-2 secretion, thus pointing to T cell recognition of both thyroid-specific and DR antigens. Evaluation of the function of the thyroid stimulated T cells revealed very potent suppressor but negligible helper and cytotoxic activities. It would seem, therefore, that DR-restricted T cell activation by autologous antigen on non-autoimmune thyroid cells does occur, but since it results in enhanced suppression, its nature seems protective, thus leading to maintenance of immunological self-tolerance.     

Human suppressor T cells: Induction, differentiation, and regulatory functions

T-cell-mediated suppression of human immune responses involves a complex interaction between distinct lymphocyte subsets with suppressor-inducer and suppressor-effector functions. Recent studies with subset-specific monoclonal antibodies have defined a characteristic phenotype of suppressor-inducer cells (CD4⁺ Leu8⁺ 2H4⁺ 4B4⁻) that can be distinguished from that of helper cells for antibody synthesis (CD4⁺ Leu8⁻ 2H4⁻ 4B4⁺). Similarly, suppressor-effector cells (CD8⁺ CD11⁺ Tp44⁻ can typically be defined as a subset separable from cytotoxic T cells (CD8⁺ CD11⁻ Tp44⁺). Both antigen-specific and nonspecific interactions are important in suppressor T-cell activation and function. Soluble signals required for differentiation of CD8⁺ suppressor cells include an indomethacin-sensitive monocyte product and interferon gamma. In contrast, proliferation of the CD8⁺ suppressor cell subset depends on stimulations first by a product of CD4⁺ Leu8⁺ cells, T suppressor cell growth factor, and second by interleukin 2. Although the molecular basis of antigen-specific interactions between CD4⁺ and CD8⁺ cells in suppressor cell generation has not been defined, it may involve both conventional, presumably MHC-restricted, interactions between antigen and antigen receptors, as well as anti-idiotypic interactions of suppressor-effectors with determinants on suppressor-inducer receptors. Progress in elucidating requirements for activation, growth, and differentiation of suppressor cells should facilitate long-term culture of such cells and lead to clearer understanding of mechanism of suppressor-cell mediated immunoregulation.     

Intrathyroidal lymphocyte subsets, including unusual CD4+ CD8+ cells and CD3loTCR alpha beta lo/-CD4-CD8- cells, in autoimmune thyroid disease.

Intrathyroidal lymphocyte subsets were analysed in 13 euthyroid patients with autoimmune thyroid disease by two-colour flow cytometry and compared with subsets in peripheral blood. In both Graves' and Hashimoto's diseases, proportions of intrathyroidal CD5- B cells were higher than in peripheral blood. The numbers of such cells were correlated with serum levels of anti-thyroid microsomal antibodies. Proportions of T cells bearing alpha beta chains of T cell receptors (TCR alpha beta+ T; T alpha beta) and CD16+CD57+ natural killer (NK) cells were lower in the thyroid, but proportions of CD3hiTCR alpha beta-TCR gamma delta+ (T gamma delta) cells were not different. Proportions of CD4+Leu-8- helper T cells and CD4+CD57+ germinal centre T cells were higher and proportions of CD4+Leu-8+ suppressor-inducer T cells and CD8+CD57+ or CD8+CD11b+ suppressor T cells were lower than in the blood in both diseases. Proportions of CD5+ B cells were high in Graves' disease, and proportions of CD8+CD11b- cytotoxic T cells were high in Hashimoto's disease. Unexpectedly, CD4+CD8+ cells and CD3loTCR alpha beta lo/-CD4-CD8- cells were present in thyroid tissues of both diseases. These findings suggest that: (i) an imbalance in the numbers of regulatory T cells and of NK cells that had appeared in the thyroid resulted in the proliferation of CD5- B cells, which were related to thyroid autoantibody production; (ii) CD5+ B cells and cytotoxic T cells are important for the different pathological features in Graves' and Hashimoto's diseases, respectively; and (iii) intrathyroidal CD4+CD8+ cells and CD3loTCR alpha beta lo/-CD4-CD8- cells may be related to the pathogenesis of autoimmune thyroid disease.     

The behaviour of suppressor-inducer T cells following treatment for Graves' disease

The expression of surface markers of T cell subsets in the peripheral blood of 30 Graves' disease patients was investigated pre and post therapy using two colour flow cytometry. Reduced numbers of total, helper/inducer and suppressor/cytotoxic T cells were found in untreated Graves' patients. Numbers of suppressor-inducer T cells which are associated with maintaining the normal immune response, did not differ significantly between untreated Graves' patients and controls. Although 8 weeks' Carbimazole therapy reversed the changes in total, helper/inducer and suppressor/cytotoxic T cells, PTU or 131I therapy did not. While suppressor-inducer T cell numbers were not affected by Carbimazole or PTU therapy, 131I treatment caused a decrease in suppressor-inducer T cell numbers.     

Correlation of immunoregulatory function with cell phenotype in cord blood lymphocytes.

The strong suppressor activity of cord T lymphocytes contrasts markedly with their mainly CD4 (helper) rather than CD8 (suppressor) phenotype. We studied the phenotype of cord CD3, CD4 and CD8 cells compared to adult cells using the monoclonal antibodies, 2H4, 4B4, and UCHL1. Almost all cord CD4 lymphocytes carried the suppressor-inducer marker 2H4, whereas 4B4+ UCHL1+ helper-inducer cells were virtually absent; CD8 cord cells were also of the 2H4+ 4B4- UCHL1- phenotype. In contrast in adult peripheral blood, half of the T cells, whether CD4 or CD8, were 2H4+ and half 4B4/UCHL1+. The suppressor-inducer phenotype of cord T cells was shown, in parallel functional experiments, to correlate with their enhanced proliferation to lectin and poor production of immunoglobulin and with the ability of cord mononuclear cells to suppress proliferation and immunoglobulin production by adult cells in co-culture experiments. These results indicate that the major imbalance in the cord CD4 subset in favour of 2H4 cells can explain many of the functional differences from adult cells. However, involvement of other cell types, in particular of the monocyte lineage, is necessary to explain other properties of immunocompetent cord cells.     

Phenotypic identification of suppressor-effector, suppressor-amplifier and suppressor-inducer T cells of B cell differentiation in man

Using monoclonal anti-Leu8 antibody to isolate subpopulations of human helper/inducer (CD4+) and suppressor/cytotoxic (CD8+) T cells, we have investigated the role of these subpopulations in the regulation of B cell differentiation in the human autologous mixed leukocyte reaction (AMLR). Whereas AMLR-activated CD8+,Leu8- cells were capable of suppressing fresh AMLR cultures in the absence of fresh CD8+ cells, CD8+,Leu8+ cells suppressed only those cultures containing fresh CD8+ cells. On the other hand, CD8+,Leu8- cells became suppressor cells only when cultured in the presence of CD8+,Leu8+ cells. Finally, the development of CD8+ suppressor cells was dependent on the presence of CD4+,Leu8+ cells; CD4+,Leu8- cells were incapable of acting as suppressor-inducer cells, but have been shown previously to mediate T cell help for B cell differentiation. Thus, at least 3 phenotypically distinct subsets of T cells interact sequentially to generate suppression of B cell differentiation induced in the AMLR: CD4+,Leu8+ suppressor/inducer cells, CD8+,Leu8+ suppressor-amplifier cells and CD8+,Leu8- suppressor-effector cells.     

Characterization of human T8+ suppressor and contrasuppressor cells, separated by the lectin Vicia villosa.

The helper function of human T4+ cells acting on autologous B cells, in the presence of monocyte-enriched cells (MEC), has been studied using the hapten-carrier conjugate DNP-streptococcal antigen (DNP-SA). The antibody response can be suppressed by T8+ cells, but selection of a Vicia villosa lectin-non-adherent (T8VV-) subset enhances the suppressor function. The T8 Vicia villosa lectin-adherent (T8VV+) cells are not suppressive, rather they inhibit the T8VV- cell suppressor function. Sequential reconstitution studies suggest that the target of both T8VV- suppressor-cell and T8VV+ contrasuppressor activity is the T4 helper-inducer cell. This was established after the separation of T4+ cells into Leu 8- helper- and Leu 8+ suppressor-inducer cells. Activation of T8VV- and T8VV+ cells with antigen before reconstitution with fresh lymphocytes and MEC suggests that T8VV- suppressor activity is antigen specific, whereas T8VV+ cell contrasuppressor function is non-specific. We suggest that the human T8+ cells are functionally heterogeneous and consist not only of suppressor and cytotoxic cells but also contrasuppressor cells.     

Deficiency of suppressor-inducer (CD4+CD45RA+) T cells in autism

CD4+ cells are a heterogenous population of lymphocytes including at least two distinct subpopulations: CD45RA+ cells, inducers of suppressor T cells and CDw29+ cells, inducers of helper function for antibody production. To investigate the possibility that immune abnormalities in autism may involve abnormal distribution of these helper subpopulations, monoclonal antibodies were used in flow cytometric analysis to characterize peripheral blood lymphocytes of 36 subjects with autism. The autistic subjects as compared to a group of 35 healthy age-matched subjects had a significantly reduced number of lymphocytes, a decreased number of CD2+ T cells and reduced numbers of CD4+ and CD4+CD45RA+ lymphocytes. The numbers of B (CD20+) cells, suppressor T (CD8+) cells, inducers of helper function (CD4+CDw29+) and natural killer (CD56+) cells were not altered in the autistic subjects. Our results suggest that an alteration in the suppressor-inducer T-cell subset is associated with autism.     

Heterogeneity of concanavalin A-induced suppressor T cells in man defined with monoclonal antibodies.

Human peripheral blood T lymphocytes were enriched for OKT4+ or OKT8+ subpopulations using complement mediated lysis with OKT8 or OKT4 monoclonal antibodies. These subpopulations and unfractionated T cells were separately stimulated with concanavalin A (Con A) for a period of 48 hr and were then examined for their suppressive influence on proliferative response of autologous T cells to phytohaemagglutinin (PHA) or allogeneic non-T cells. Con A-activated unfractionated T cells, OKT4+ and OKT8+ T cell subsets markedly suppressed both these responses. Both OKT4+ and OKT8+ T cell subsets when enriched following Con A-activation of unfractionated T cells also caused significant suppression of proliferative responses of autologous T cells to PHA and allogeneic non-T cells in mixed lymphocyte cultures. The suppressive influence of Con A-activated T subsets was abolished by irradiation (2,000 rad) of activated cells. These studies indicate that Con A-induced suppressor T cells are heterogeneous. Precursors of Con A-induced suppressor T cells appear to reside in both OKT4+ and OKT8+ T cell populations.     

Immunoregulatory CD4+ CD45R+ suppressor/inducer T lymphocyte subsets and impaired cell-mediated immunity in patients with Down''s syndrome.

The monoclonal antibodies 2H4 and 4B4 allow CD4+ and CD8+ T lymphocytes to be subdivided into CD45R+ and CDW29+ functional subpopulations. The CD4+ CD45R+ lymphocytes are designated as suppressor/inducer and CD4+ CDW29+ as helper/inducer subsets. Peripheral blood lymphocytes from 19 patients with Down's syndrome and 19 age- and sex-matched normal controls were analysed for the CD45R+ and CDW29+ subsets from the CD4+ and CD8+ T lymphocytes. The percentage of CD4+ CD45R+ cells (suppressor inducer) was markedly increased and of CD4+ CDW29+ cells (helper/inducer) decreased in all patients with Down's syndrome. In contract, the percentage of CD8+ CD45R+ and CD8+ CDW29+ subsets showed no major differences between patients with Down's syndrome and normal controls. Moreover, an alteration in the CD4+ and CD45R+ and CD4+ CDW29+ T cell subsets was accompanied by a markedly reduced proliferative response to phytohaemagglutinin and concanavalin A stimulation of the CD4+ T lymphocytes. Thus, a deficiency exists in patients with Down's syndrome in the CD4+ CDW29+ helper/inducer T cell subset which may contribute to their impaired cell-mediated immunity.     

Lymphocyte transformation induced by autologous cells: XVIII. Impaired autologous mixed lymphocyte reaction in subjects with AIDS-related complex.

T cells from patients with AIDS-related-complex (ARC) and normal controls were studied for their proliferative response in the autologous mixed lymphocyte reaction (AMLR). Cells from ARC subjects failed to proliferate in autologous MLR compared to normal controls. This defect was not attributable to an altered ratio of T4 to T8 cells, as purified T4 cells from ARC subjects also failed to proliferate in autologous mixed lymphocyte culture. In contrast, T cells from ARC subjects proliferated normally in response to allogeneic non-T cells, and non-T cells from ARC patients stimulated allogeneic T cells as well as did non-T cells from normal controls. Furthermore, there was no significant alteration in the 2H4 (suppressor-inducer) or 4B4 (helper-inducer) subsets of the T4 cell population in these patients. We conclude that an early immunologic defect that accompanies HTLV-III infection is a loss of the T cell response to autologous non-T cells.     

T cell malignancy in Richter's syndrome presenting as hyper IgM. Induction and characterization of a novel CD3+, CD4-, CD8+ T cell subset from phytohemagglutinin-stimulated patient's CD3+, CD4+, CD8+ leukemic T cells

A patient is described, having Richter's syndrome and immunodeficiency with hyper IgM, who developed suppressor T cell lymphoma (CD3+, CD4-, CD8+) following untreated helper-suppressor T cell chronic lymphocytic leukemia (CD3+, CD4+, CD8+). The neoplastic T cells in both malignancies expressed interleukin (IL) 2 receptors but were deficient in typical CD2+ and CD5+ pan T antigens. Additionally, a large percentage of malignant lymph node T cells expressed HLA-DR+ activation antigens. In vitro immunoglobulin-production experiments demonstrated that the patient's leukemic blood T cells had an excess helper function for IgM synthesis but a suppressor function for IgG and IgA synthesis by normal B and T cells. The leukemic blood T cells demonstrated a poor response to phytohemagglutinin (PHA). A defect in IL 2 receptor expression was evident in PHA-stimulated leukemic blood T cells. Of interest was the observation that PHA stimulated the induction of a novel CD3+, CD4-, CD8+ T cell subset from patient's CD3+, CD4+, CD8+ leukemic blood T cells. These PHA-induced CD3+, CD4-, CD8+ T cell subsets produced an elevated proliferative response to PHA and concanavalin A, had a helper cell function for IgM synthesis and produced highly elevated amounts of IL 2.     

Activation of immune regulatory circuits among OKT4+ cells by autologous mixed lymphocyte reactions

We examined the nature of an autologous mixed lymphocyte reaction (AMLR) using T cell subsets defined by monoclonal antibodies. Cells capable of proliferating in the AMLR were demonstrated to reside in an OKT4+, but not an OKT8+, cell subset. With regard to the role of the T cell subsets recoverable from AMLR in the immune regulation, OKT4+ cells isolated from cells that had been activated for 3 days in AMLR did help pokeweed mitogen (PWM) stimulated immunoglobulin synthesis by autologous B cells. However, the OKT4+ cells activated for 6 days in AMLR exerted strong suppressor activity for PWM-induced immunoglobulin synthesis. Irradiation with 1,500 rad on activated OKT4+ cells in AMLR for 6 days not only eliminated the suppressor function but allowed for re-emergence of helper function. Cells exerting suppressor activity alone were recovered from OKT8+ cells stimulated with or without autologous non-T cells. These data suggest that OKT4+ cells activated in AMLR contain two functionally different subsets; one as helper cells and the other as suppressor cells. In addition, the emergence of OKT4+ suppressor function follows activation of the OKT4+ helper population, suggesting that a part of AMLR reflects a mechanism of 'feedback suppression' among OKT4+ cells.     

Establishment of stable CD8+ suppressor T cell clones and the analysis of their suppressive function.

Stable CD8+ suppressor T cell (Ts) clones were established by a relatively simple method. Keyhole limpet hemocyanin (KLH)-primed spleen cells from C3H mice were depleted of B cells and CD4+ T cells by panning and cytotoxic treatment, and the resulting CD8+ T cells were periodically stimulated with antigen and irradiated syngeneic spleen cells followed by manifestation in interleukin-2 (IL-2) containing medium. T cell clones with a definite suppressor function were established by limiting dilution. They were defined as classical effector type Ts of CD8+ phenotype as they had constant and definite suppressor functions in antigen-induced T cell proliferation and specific antibody response against T cell-dependent antigens without detectable cytotoxic activity against both antigen presenting cells (APC) and helper T cells (Th). They showed no helper activity for B cells and produced no detectable helper type lymphokines such as IL-2 and IL-4. CD8+ Ts clones were able to inhibit the antigen-induced IL-2 production of normal and cloned T cells. Their suppressive activity was antigen-nonspecific and major histocompatibility complex-unrestricted. CD8+ Ts clones were also able to suppress the proliferative response of Th clones induced by immobilized anti-T cell receptor (TcR) and anti-CD3 mAbs but not the response induced by concanavalin A (ConA) and IL-2. All the CD8+ T cell clones established independently utilized the TcR V beta 8 gene. Syngeneic antigen presenting cells could induce proliferation of these CD8+ clones, which was blocked by anti-CD8 and anti-I-Ak monoclonal antibody (mAb) but not by anti-class I mAbs. The stimulation of CD8+ Ts clones with immobilized anti-CD3 resulted in the release of a suppressor factor(s) that potently inhibited the antigen-induced proliferation of CD4+ Th clones and the in vitro secondary antibody formation.     

IL-2 normalizes defective suppressor T cell function of patients with systemic lupus erythematosus in vitro

During autologous mixed lymphocyte reaction (AMLR) both helper and suppressor T cells capable of regulating B cell responses are generated. The proliferative response of T cells as well as the generation of T suppressor cells in the AMLR of patients with active systemic lupus erythematosus (SLE) is diminished. In contrast, the T helper cells generated in the AMLR show a hyperactivity. The diminished HLA-class II antigen expression observed on non-T cells of SLE origin was restored by treatment of the cells with gamma-interferon (gamma-IFN). When tested by immunoglobulin secretion, gamma-IFN enhanced T helper cell activity but failed to affect T cell proliferation and T suppressor cell generation in the AMLR derived from patients with SLE. Human recombinant interleukin 2 restores both the proliferative response of T cells and the induction of T suppressor cells in AMLR.     

Selective sensitization of peripheral blood T lymphocytes to hepatitis B core antigen in patients with chronic active hepatitis type B.

The proliferative response of peripheral blood T cells to hepatitis B surface antigen (HBsAg), pre-S antigen and hepatitis B core antigen (HBcAg) has been studied in 20 patients with hepatitis B virus induced chronic active hepatitis (CAH) and in 12 control subjects. Eleven of the 20 CAH patients showed a significant T lymphocyte proliferative response to HBcAg, whereas no proliferation was detectable in response to envelope antigens (HBs and pre-S) in any patient. T cell subset fractionation revealed that HBcAg specific proliferation was limited to the CD4+ (helper/inducer) population. CD8+ (suppressor/cytotoxic) T cells were unresponsive to HBcAg and did not suppress the proliferative response of autologous CD4+ cells. The HBcAg specific T cell proliferative response did not correlate with serum anti-core antibody titres or with biochemical evidence of liver disease. The present results show the selective presence of HBcAg-sensitized T cells in the peripheral blood of patients with HBsAg positive CAH and suggest that the peripheral lymphoid compartment may not reflect immunopathogenetically important cellular events operative at the site of tissue injury.     

Induction of suppression following autologous mixed lymphocyte reaction; role of a novel 2H4 antigen

In this study, we have investigated the cellular and molecular basis for immunoregulatory function of T4+ cells after autologous mixed lymphocyte reaction (AMLR) activation. We demonstrated that the T4+ 2H4+ subset but not the T4+2H4- subset can proliferate maximally in response to autologous non-T cells. T4+ cells activated by AMLR exerted suppressor activity on pokeweed mitogen-driven IgG synthesis of autologous peripheral blood lymphocytes. The suppressor activity by AMLR-activated T4+ cells required the presence of fresh T8+ cells in the secondary culture, indicating that AMLR-activated T4+ cells functioned as a suppressor inducer rather than as a suppressor effector population. Following activation of T4+ cells in AMLR, it is the T4+2H4+ subset which induces suppression through the T8 population. Moreover, the treatment of AMLR-activated T4+2H4+ cells with anti-2H4 antibody, but not other antibodies, resulted in the abolishment of suppressor inducer function of such cells, suggesting that the 2H4 molecule itself may be involved in the suppressor inducer function. The 2H4 antigen on such cells was shown to be comprised of 220-kDa and 200-kDa glycoproteins. These results support the notion that the AMLR may play an important role in generating suppressor inducer signals and in down-regulating the immune response following self major histocompatibility complex recognition. More importantly, the present studies indicate that the 2H4 antigen on T4 cells serves not only as a phenotypic marker of suppressor inducer cells, but may have a functionally important role itself inducing suppression.     

In vivo depletion of BoT4 (CD4) and of non-T4/T8 lymphocyte subsets in cattle with monoclonal antibodies

The effect on certain immune responses of depleting two distinct lymphocyte subpopulations in vivo by inoculating calves with monoclonal antibodies (mAb) was examined. An mAb directed against the BoT4 antigen (the bovine homologue of CD4) effectively removed the BoT4+ lymphocytes from peripheral blood mononuclear cells (PBM). Compared to controls, treated calves showed a reduced antibody response to human O red blood cells and to ovalbumin. PBM prepared from BoT4-depleted animals also had a significantly reduced ability to respond in vitro to the mitogens phytohemagglutinin, concanavalin A and pokeweed mitogen. An mAb directed against a second numerically large bovine lymphocyte subpopulation i.e. BoT2-, BoT4-, BoT8- (CD2-, CD4-, CD8-), that may be homologous to the CD4-, CD8- cells in man and rodents that synthesize the gamma/delta+ T cell receptor, was also used for in vivo depletion. Compared to controls, calves depleted of this subpopulation showed an enhanced antibody response. The proliferative response of PBM to pokeweed mitogen was also significantly increased but responses to concanavalin A and phytohemagglutinin remained unchanged. The results suggest this lymphocyte subpopulation has a nonspecific suppressor activity acting on B cell responses either directly or through an effect on T helper cells. The non-T4/T8 cells are found extensively in the epithelium and lamina propria of the mucosa of the alimentary tract but not in T cell areas of the lymph nodes, tonsil and spleen. These non-T4/T8 cells may thus be, or contain, an intraepithelial lymphocyte population with a suppressor function.     

Autologous Mixed Lymphocyte Reaction in Man

Human peripheral T cells and T-cell Subpopulations defined with monoclonal antibodies of the OKT series were studied for the proliferative response on stimulation with autologous non-T cells or mitogen-activated T cells as stimulators in autologous mixed lymphocyte reaction (AMLR). T cells exhibited a vigorous proliferative response when stimulated with autologous non-T cells or activated T cells but not with unactivated T cells. The stimulatory capacity of non-T cells or activated T cells in AMLR was inhibited by prior treatment of stimulator cells with 7, 2 anti-human Ia framework-specific monoclonal antibody in the absence of complement. A BUdR and light technique was used to ablate proliferating T cells in response to either non-T cells or activated T cells in AMLR. The removal of T cells responding to autologous non-T cells left the responsiveness to autologous activated T cells relatively intact. Conversely, the removal of T cells responding to autologous activated T cells left the responsiveness 10 autologous non-T cells relatively intact. Thus T cells responding to autologous non-T cells appear to be distinct from those responding to autologous activated T cells in AMLR. Further analysis with OKT4 and OKT8 monoclonal antibodies showed that the major population responding to autologous non-T cells was contained in OKT4⁺ T cells and that responding to autologous activated-T cells was contained in OKT8⁺ T-cell subset. However, both OKT4⁺ and OKT8⁺ T-cell subsets responded by proliferation to non-T cells and activated T cells in allogeneic MLR. T cells selected after AMLR between T and non-T cells or T and activated T cells were treated with mitomycin and examined for their regulatory influence on the proliferative response of fresh autologous responder T cells. T cells selected from T and non-T AMLR augmented and those obtained from T and activated T AMLR suppressed the proliferative responses of fresh autologous T cells to phytohaemagglutinin and to autologous or allogeneic non-T cells in AMLR or allogeneic MLR. These findings indicate that in AMLR between T and non-T cells or T and activated T cells phenotypically distinct Subpopulations of T lymphocytes respond by proliferation and express distinct immunoregulatory functions.