Production of lymphokines by circulating human T lymphocytes that express or lack receptors for interleukin 2

The capacity for circulating human T cells which have or lack receptors for interleukin 2 (IL 2) to produce IL 2, interleukin 3 (IL 3), and interferon-gamma (IFN-gamma) under the stimulus of phytohemagglutinin was studied. By using the monoclonal anti-Tac antibody which reacts against IL 2 receptors on human T cells, concanavalin A-treated T cells were separated into IL 2 receptor-positive (Tac+ T cells) and IL 2 receptor-negative (Tac- T cells) lymphocytes. The results show that Tac+ T cells secreted IL 2 and IFN-gamma but not IL 3. Tac- T cells produced IL 2 and IL 3 but not IFN-gamma. It is concluded that: 1) both T cells lacking and T cells having receptors for IL 2 produce IL 2, but only IL 2 receptor-negative T cells appear to secrete IL 3; and 2) virtually all of the T cells that produce IFN-gamma after PHA stimulation express receptors for IL 2.

Production of lymphokines by circulating human T lymphocytes that express or lack receptors for interleukin 2

The capacity for circulating human T cells which have or lack receptors for interleukin 2 (IL 2) to produce IL 2, interleukin 3 (IL 3), and interferon-gamma (IFN-gamma) under the stimulus of phytohemagglutinin was studied. By using the monoclonal anti-Tac antibody which reacts against IL 2 receptors on human T cells, concanavalin A-treated T cells were separated into IL 2 receptor-positive (Tac+ T cells) and IL 2 receptor-negative (Tac- T cells) lymphocytes. The results show that Tac+ T cells secreted IL 2 and IFN-gamma but not IL 3. Tac- T cells produced IL 2 and IL 3 but not IFN-gamma. It is concluded that: 1) both T cells lacking and T cells having receptors for IL 2 produce IL 2, but only IL 2 receptor-negative T cells appear to secrete IL 3; and 2) virtually all of the T cells that produce IFN-gamma after PHA stimulation express receptors for IL 2.

Distinct mechanisms may account for the growth-promoting activity of interleukin 3 on cells of lymphoid and myeloid origin

We have investigated whether interleukin 3 (IL-3) supports the growth of cells of different lineages by the same mechanism(s). The experiments were carried out with Ea3 cells, a mouse pre-B cell line, and S-480-3 cells, a mouse basophil cell line, both of which are totally IL-3 dependent. We found that Ea3 lymphocytes but not S-480-3 basophils absorb partially purified IL-3. Both Ea3 and S-480-3 cells respond to IL-3 by increasing anaerobic glycolysis as determined by lactic acid production. S-480-3 cells responded to exogenous ATP by maintaining proliferation and reducing lactic acid production, but Ea3 lymphocytes are refractory to exogenous ATP. We conclude that there may be two distinct mechanisms by which cells respond to IL-3, indicated by early events concerning the binding of IL-3 and the effect of exogenous ATP on respiratory metabolism. One appears to be a ligand-receptor-mediated mechanism in lymphoid cells and the other to be a mechanism that is partially replaceable by exogenous ATP in nonlymphoid cells not associated with lymphoid-like receptors. Our findings may explain (i) the apparent variety of cell lineages promoted by IL-3 by a widely available mechanism that supports glycolysis and, therefore, enables both proliferation and possibly expression of binding sites for lineage specific differentiation factors and (ii) the existence of lymphocytes that express receptors specific for IL-3 and are inducible for other characteristics and functions in a regulated manner.

Genetic and biochemical characterization of glutamine synthetase from Neurospora crassa glutamine auxotrophs and their revertants

In this paper we present the isolation and characterization of glutamine auxotrophs of Neurospora crassa and their revertants. The results show that although various enrichment procedures were used, we found only two types of auxotrophs. Genetic crosses performed between the different mutants showed that the mutations responsible for their phenotypes were highly linked and probably affected the same gene. The biochemical characterization of the glutamine synthetase polypeptides of the different mutants showed that both types contained the alpha monomer. However, in place of the normal beta monomer, each type had a new polypeptide differing from normal beta either in its molecular weight or in its isoelectric point. On the other hand, the revertants had only the alpha monomer and were capable of growing without glutamine. On the basis of these data, we propose that the lack of glutamine synthetase activity in the auxotrophs is due to the interaction of the altered beta with the alpha monomer, and as a consequence the alpha monomer of the revertants regains its activity because of the absence of the altered beta.

Monoclonal antibodies against HLA-DR antigens replace T helper cells in activation of B lymphocytes

In the presence but not in the absence of pokeweed mitogen (PWM), monoclonal antibodies against HLA-DR antigens 147 and 164 helped highly purified B lymphocytes to proliferate and mature to Ig-secreting cells. In contrast, neither anti-DR antibody 231 nor the UCHT1 monoclonal anti-human T cell antibody (both of the same isotype as the 147 and 164 anti-DR antibodies) exhibited any helper activity on B cells. B cells pulsed with PWM and subsequently cultured in the presence of anti-DR antibody 147 or 164 proliferated and secreted Ig, whereas B cells that first were pulsed with antibody 147 or 164 and then incubated with PWM did not. PWM alone did not induce any of these responses on purified B cells. Also, antibodies 147 and 164 significantly increased the number of Ig-secreting cells obtained from the WT51 Epstein-Barr virus-transformed B-cell line. Anti-DR antibody 231 inhibited the helper activity on WT51 cells mediated by anti-DR antibody 164. Finally, anti-DR antibodies 147 and 164 assisted B cells from the spleen of athymic nu/nu mice (which bear I-E-encoded products) to produce IgM antibodies against sheep erythrocytes. However, these antibodies had no effect on mouse B cells which do not express on their surface I-E-encoded Ia antigens. Taken collectively, these findings suggest that the structures detected by anti-DR antibodies 147 and 164 on B lymphocytes function as acceptors/transducers of T-cell-derived helper signals.

Nitrogen source regulates glutamate dehydrogenase NADP synthesis in Neurospora crassa

Neurospora crassa glutamate dehydrogenase-NADP (EC 1.3.1.3) has a higher activity when mycelium is grown on ammonium or nitrate as nitrogen source than when grown on glutamate or glutamine. Quantitative immunoelectrophoresis established that, under all conditions, enzyme activity corresponded to enzyme concentration. Isotope incorporation studies demonstrated that the nitrogen source exerts its regulation at the level of de novo enzyme synthesis.

Production of human immune interferon (Hu IFN-gamma) studied at the single cell level. Origin, evidence for spontaneous secretion and effect of cyclosporin A

A reverse hemolytic plaque assay has been developed which specifically detects secretion of human immune interferon (Hu IFN-gamma) at the single cell level. Unstimulated peripheral blood lymphocytes from healthy adult volunteers spontaneously secreted IFN-gamma. Stimulation of these cells with concanavalin A, phytohemagglutinin, or the UCHT1 monoclonal anti-human T cell antibody significantly increased the number of IFN-gamma-secreting cells. The cell producing IFN-gamma, both spontaneously and after UCHT1 antibody stimulation, is an OKT3+,4+,8-,HLA-DR-T lymphocyte as determined at the single cell level. Finally, cyclosporin A, a potent and selective immunosuppressive drug for T cells, strongly inhibited the secretion of IFN-gamma as assayed at the cell level. This IFN-gamma reverse hemolytic plaque assay has great potential for the further study of IFN-gamma both in physiological and pathological conditions.

Accessory function of human tumor cell lines. I. Production of interleukin 1 by the human histiocytic lymphoma cell line U-937

The established human histiocytic lymphoma cell line U-937 spontaneously produced a factor with biological activity similar to that ascribed to interleukin 1 (IL 1). Actually, supernatants from U-937 cells promoted proliferation of thymocytes initiated by concanavalin A (Con A) and replaced the requirement of accessory cells for activation of highly purified circulating T lymphocytes induced by Con A. Phorbol myristate acetate (PMA) significantly increased the titers of the helper factor produced by U-937 cells as compared to that secreted by non-PMA-treated U-937 cells or PMA-stimulated P388D1 murine macrophage tumor cells. Generally U-937 cells did not secrete detectable IL 1 activity during the first 24-48 h of culture. However, after this initial period the level of IL 1 activity increased and reached a maximum at 5-6 days of culture. Finally, the helper factor released by U-937 cells had an apparent mol. wt. of 12000-15000 as determined by Sephadex G-100 chromatography and lacked interleukin 2 activity as shown by its inability to support growth of IL 2-addicted T cell lines. To our knowledge this is the first report of an established human cell line capable of producing IL 1.

Development and continuous growth in culture of interleukin 2-producer lymphocytes from athymic nu/nu mice

Splenocytes of nu/nu mice treated with serum thymic factor (FTS) for 3 or more days followed by stimulation with either phorbol myristate acetate (PMA) or concanavalin A (Con A) produced interleukin 2 (IL 2) as determined in two indicator systems, namely, support of growth of IL 2-dependent T cells and promotion of Con A-initiated mitogenesis of thymocytes. However, neither mitogens nor FTS alone could induce nude mice cells to product IL 2. Supernatants derived from the tumor cell line WEHI-3 (WEHI-3 conditioned media) induced and supported continuous growth in culture of Thy-1.2+, Lyt-1+2- lymphocytes from athymic nude mice capable of producing IL 2 after their stimulation by either PMA or Con A. The growth of these IL 2-producer cell lines strickly depends on the presence of WEHI-3 conditioned media, as in the absence of it they die 24-48 h later. In addition, WEHI-3 conditioned media have been supporting the growth of IL 2-producer cell lines derived from nude mice for 3 1/2 months. The helper factor contained in WEHI-3 conditioned media responsible for the above biological activity has an apparent mol. wt. of approximately 40 000 as determined by Sephadex G-100 chromatography and lacks IL 1 and IL 2 activities, but efficiently supports the growth of IL 2-producer cells derived from nude mice and the peripheral blood of normal human volunteers. These results indicate that the helper factor in WEHI-3 conditioned media which enables the generation and continuous proliferation in culture of IL 2-producer cells in nude mice is distinct from interleukin 1, IL 2 and FTS (mol. wt. 864). Finally, the possibly functional relationship of FTS and the helper factor produced by WEHI-3 cells is discussed.

Cyclosporin-A and the OKT3 monoclonal antibody exert their respective inhibitory and mitogenic activity on T cells by interacting with the same receptors

Cyclosporin-A strongly suppressed proliferation of T cells induced by the OKT3 monoclonal antibody when added at the beginning of the cultures but not when added 72 hr later. The inhibitory activity of Cyclosporin-A became apparent during the first 48 hr and was maintained throughout the culture period. Cyclosporin-A significantly inhibited binding of OKT3, but not OKT4 or OKT8, antibodies to T cells as determined by indirect immunofluorescence microscopy. In addition, Cyclosporin-A suppressed the killing of 51Cr labelled T cells mediated by OKT3 antibody plus complement, whereas Cyclosporin-A did not alter the lysis of T cells by OKT4 antibody plus complement treatment. These results strongly suggest that Cyclosporin-A and OKT3 antibody exert their respective suppressive and mitogenic activity on T cells by interacting with the same receptor.

Cyclosporin A inhibits thymus-dependent but not thymus-independent immune responses induced by dextran B512

We have compared previous studies of the immune response to dextran (Dx) B512 in thymus-deficient nu/nu and thymectomized, lethally irradiated, and bone marrow-reconstituted mice with those obtained with cyclosporin A (CyA) as a T-cell-inhibiting drug. Our data show that only immune responses to TD forms of Dx B512 are susceptible to suppression by CyA, whereas anti-alpha 1-6 and anti-DNP antibodies induced by high molecular weight dextran and DNP-native Dx, respectively, were not inhibited. Similar results were obtained when polyclonal responses were studied. The polyclonal response induced by another dextran preparation, the polyanion dextran sulphate (DxS), was inhibited by CyA to the same extent as polyclonal T-cell activation by T-cell mitogens.

Physiology of ammonium assimilation in Neurospora crassa

In Neurospora crassa the assimilation of high and low concentrations of ammonium occurs by two different pathways. When the fungi are growing exponentially on ammonium excess, this compound is fixed by a glutamic dehydrogenase and an octameric glutamine synthetase (GS). The synthesis of this GS polypeptide (beta) is regulated by the nitrogen source present in excess; being higher on glutamate, intermediate on ammonium, and lower on glutamine. When N. crassa is growing in fed-batch ammonium-limited cultures a different polypeptide of GS (alpha), arranged as a tetramer, is synthesized. In both conditions synthesis in vivo correlates with the data obtained with an in vitro translation system primed with N. crassa RNA. This different expression of alpha and beta GS polypeptides was also observed when the cultures were shifted from excess to low nitrogen, and vice versa. By agarose gel electrophoresis in the presence of methylmercury hydroxide, some separation of different mRNAs that direct the in vitro synthesis of alpha and beta GS polypeptides has been accomplished. Data are presented that establish the operation of the tetrameric alpha GS and of glutamate synthase in the assimilation of ammonium in low concentration.

Dextran-sulfate: a mitogen for human T lymphocytes

Dextran-sulfate (DxS) induced proliferation of human peripheral blood T lymphocytes but not of adult or neonatal B lymphocytes. The mitogenic activity on T cells by DxS required the presence of accessory cells because DxS was unable to trigger T cells to DNA synthesis in the absence of accessory cells. In addition, DxS stimulated OKT4+8- T cells to produce interleukin 2, a process that also occurred only in the presence of accessory cells. Cyclosporin-A strongly suppressed T cell proliferation induced by DxS by rendering T cells unresponsive to interleukin 2 and by inhibiting the synthesis of this T cell growth factor by OKT4+ T cells. These results indicate that DxS is a mitogen for human T lymphocytes but not for adult or neonatal B lymphocytes. The mechanism by which DxS triggers T cells is discussed.

Dextran-sulfate: a mitogen for human T lymphocytes

Dextran-sulfate (DxS) induced proliferation of human peripheral blood T lymphocytes but not of adult or neonatal B lymphocytes. The mitogenic activity on T cells by DxS required the presence of accessory cells because DxS was unable to trigger T cells to DNA synthesis in the absence of accessory cells. In addition, DxS stimulated OKT4+8- T cells to produce interleukin 2, a process that also occurred only in the presence of accessory cells. Cyclosporin-A strongly suppressed T cell proliferation induced by DxS by rendering T cells unresponsive to interleukin 2 and by inhibiting the synthesis of this T cell growth factor by OKT4+ T cells. These results indicate that DxS is a mitogen for human T lymphocytes but not for adult or neonatal B lymphocytes. The mechanism by which DxS triggers T cells is discussed.

Interleukin-2 and serum thymic factor enable autologous rosette-forming T lymphocytes to generate helper and cytotoxic functions

The autologous rosette-forming T cells (Tar cells) isolated by means of their ability to form rosettes with autologous erythrocytes were characterized by the use of OKT monoclonal anti-human T-cell subset antibodies and a monoclonal anti-HLA-DR antibody. We found that the phenotype of Tar cells was OKT 3+4+8+Dr- as determined by both indirect immunofluorescence microscopy and complement-mediated killing of 51Cr-labelled Tar cells. In addition, we found that Tar lymphocytes were able to develop cytotoxicity against allogeneic and trinitrophenol (TNP)-conjugated autologous target cells in the presence of interleukin-2 (IL-2) or serum thymic factor. However, these cells showed little or nor cytotoxicity in the absence of interleukin-2 or serum thymic factor. Tar lymphocytes generated helper function for B lymphocytes in the presence of interleukin-2 in both pokeweed mitogen (PWM)- and purified protein derivative (PPD)-stimulated cultures. Nevertheless, non-IL-2-treated Tar cells did not exhibit any helper activity on B cells. Finally, pretreatment of Tar cells with 1000-1500 rad of X ray made these cells unable to develop helper function for B lymphocytes. It is concluded that: (1) OKT 3+4+8+Dr- Tar cells are able to generate cytotoxicity against alloantigens and TNP-labelled self structures provided they are stimulated by IL-2 or serum thymic factor; (2) these cells need both to proliferate and to receive help from IL-2 to develop helper cells capable of assisting B-lymphocyte differentiation into plasma cells in both PWM- and PPD-stimulated cultures.

Concanavalin A triggers T lymphocytes by directly interacting with their receptors for activation

Anti-HLA-DR antibodies did not inhibit concanavalin A-(Con A) induced T cell proliferation or the generation of suppressor cells capable of inhibiting immunoglobulin synthesis in autologous mononuclear cells after pokeweed mitogen stimulation. Nylon-wool purified T cells (pretreated with anti-HLA-DR antibody and C) exposed to Con A acquired responsiveness to interleukin 2 (IL 2) and were able to absorb this growth factor, whereas nonlectin-treated cells did not respond to IL 2 and could not absorb it. In the presence of interleukin 1 (IL 1), Con A stimulated the synthesis of IL 2 in purified OKT4+ lymphocytes but not OKT8+ cells. However, in the absence of IL 1, neither resting OKT4+ nor Con A-treated OKT4+ cells produced IL 2. Con A by itself did not directly stimulate macrophages to synthesize IL 1, although it could do so in the presence of OKT4+ but not OKT8+ lymphocytes. In addition, Con A induced proliferation of purified T cells provided IL 1 was supplied to the cultures. Cyclosporin A rendered Con A-treated T cells unresponsive to IL 2, made lectin-stimulated OKT4+ lymphocytes unable to respond to IL 1, and inhibited the synthesis of IL 2. Furthermore, this drug abrogated the Con A-stimulated synthesis of IL 1 by acting on OKT4+ lymphocytes and not on macrophages. Finally, cyclosporin-A suppressed the proliferative response and the generation of suppressor T cells induced by Con A. The following are concluded: 1) HLA-DR antigens do not seem to play any role in the triggering of T cells by Con A, and macrophages participate in lectin-induced activation of T cells mainly by providing IL 1. 2) Cyclosporin-A inhibits activation of T cells by interfering with the mechanism by which Con A stimulates T lymphocytes. 3) Con A triggers T lymphocytes by directly interacting with their receptors for activation.

Concanavalin A triggers T lymphocytes by directly interacting with their receptors for activation

Anti-HLA-DR antibodies did not inhibit concanavalin A-(Con A) induced T cell proliferation or the generation of suppressor cells capable of inhibiting immunoglobulin synthesis in autologous mononuclear cells after pokeweed mitogen stimulation. Nylon-wool purified T cells (pretreated with anti-HLA-DR antibody and C) exposed to Con A acquired responsiveness to interleukin 2 (IL 2) and were able to absorb this growth factor, whereas nonlectin-treated cells did not respond to IL 2 and could not absorb it. In the presence of interleukin 1 (IL 1), Con A stimulated the synthesis of IL 2 in purified OKT4+ lymphocytes but not OKT8+ cells. However, in the absence of IL 1, neither resting OKT4+ nor Con A-treated OKT4+ cells produced IL 2. Con A by itself did not directly stimulate macrophages to synthesize IL 1, although it could do so in the presence of OKT4+ but not OKT8+ lymphocytes. In addition, Con A induced proliferation of purified T cells provided IL 1 was supplied to the cultures. Cyclosporin A rendered Con A-treated T cells unresponsive to IL 2, made lectin-stimulated OKT4+ lymphocytes unable to respond to IL 1, and inhibited the synthesis of IL 2. Furthermore, this drug abrogated the Con A-stimulated synthesis of IL 1 by acting on OKT4+ lymphocytes and not on macrophages. Finally, cyclosporin-A suppressed the proliferative response and the generation of suppressor T cells induced by Con A. The following are concluded: 1) HLA-DR antigens do not seem to play any role in the triggering of T cells by Con A, and macrophages participate in lectin-induced activation of T cells mainly by providing IL 1. 2) Cyclosporin-A inhibits activation of T cells by interfering with the mechanism by which Con A stimulates T lymphocytes. 3) Con A triggers T lymphocytes by directly interacting with their receptors for activation.

Hydrocortisone abrogates proliferation of T cells in autologous mixed lymphocyte reaction by rendering the interleukin-2 Producer T cells unresponsive to interleukin-1 and unable to synthesize the T-cell growth factor

Hydrocortisone (HC-A) inhibited the proliferative response in the autologous mixed lymphocyte reaction (AMLR). The inhibitory activity became apparent 48 h after initiation of the cultures and was maintained throughout the culture period. T cells from cultures treated with HC-A showed a proliferative response to interleukin-2 (IL-2) of a similar degree as T cells from cultures not exposed to this drug. Hydrocortisone abrogated the production of IL-2 in AMLR. The addition of interleukin-1 (IL-1) to HC-A-treated cultures did not restore or increase the synthesis of IL-2, whereas IL-1 added to non HC-A treated cultures significantly enhanced the synthesis of IL-2, Finally, IL-2 but not IL-1 could overcome the abrogatory effect of hydrocortisone on proliferation of T cells induced by AMLR. These results indicate that HC-A inhibits proliferation of T cells in AMLR by causing the IL-2 producer T cells to become unresponsive to IL-1 and unable to synthesize IL-2. This drug does not, however, interfere with the process by which resting T cells acquire responsiveness to IL-2.

Epstein-Barr virus increases the proliferative response and the generation of suppressor and cytotoxic T-cell functions in autologous mixed lymphocyte reaction

Epstein-Barr virus (EBV) infection of stimulator cells significantly increased the proliferative response of T cells in the autologous mixed lymphocyte reaction (AMLR). The addition of a monoclonal anti-HLA-DR antibody to AMLR cultures in which either EBV-infected or non-infected non-T cells were used as stimulator cells strongly inhibited the proliferative response irrespective of the presence of EBV. It is concluded that EBV does not by itself activate the responding cells and that HLA-DR antigens are necessary to trigger T cells. Increased generation of suppressor T cells, determined in both alloantigen-induced DNA synthesis and pokeweed-mitogen-stimulated immunoglobulin production, was found after an EBV infection of stimulator cells. Similarly, EBV-infected non-T cells significantly increased the generation of killer T cells, determined in three different types of target cells: phytohaemagglutinin-stimulated mononuclear cells, EBV-transformed cells, and concanavalin-A-activated murine spleen cells. The increased T-cell responses after an EBV infection may reflect the attempts in vivo to control and hold in check the viral infection.

Human postthymic precursor cells in health and disease. IV. Abnormalities in immunoregulatory T cell circuits in mixed connective tissue disease

Human T cells are capable of forming rosettes with autologous erythrocytes (Tar cells) and behave as postthymic precursors. Thus, they generate Tgamma and Tmu cells as well as suppression and spontaneous cytotoxicity and participate in a pokeweed mitogen-driven system akin to that of feedback inhibition in which murine postthymic precursors participate. Tar cells were increased in 7 patients with mixed connective tissue disease (MCTD) compared to normal age/sex-matched controls. Despite this increase of precursor cells, decreased Tgamma cells and abrogation in the generation of suppression and of feedback inhibition were noted. These functional defects were not correctable with serum thymic factor but could be corrected by the addition of either allogenic Tmu or mononuclear cells depleted of Tar cells. Our findings suggest that the immunoregulatory T cell circuits in MCTD may be adequate both in postthymic precursor cells and in the thymic factor prompting. They are probably abnormal either at the site of Tmu signaling to Tar cells in feedback inhibition or in the Tmu reception of suppressor signals from Tgamma cells. The decrease of Tgamma cells in MCTD could be due to the decreased stimulus from feedback inhibition and/or to the penetration of anti-ribonucleoprotein antibody. Abnormalities of immunoregulatory T cell circuits in MCTD are quite different from those found previously in systemic lupus erythematosus, scleroderma, and rheumatoid arthritis. These differences support the notion that MCTD is a distinct entity.

Cyclosporin A abrogates proliferation of T cells and generation of suppressor and cytotoxic T-cell function induced by Epstein-Barr virus

Cyclosporin A (CYA) promotes the outgrowth in vitro of Epstein-Barr-virus(EBV)-infected cells of immune donors. In the present study, the effects of CYA on the T-cell responses developed to an in-vitro EBV infection were studied. Cyclosporin A, by acting on the responder cells and not on stimulator cells, strongly inhibited the proliferation of T cells normally induced by EBV-infected autologous cells. Moreover, T cells from cultures not exposed to CYA exerted suppression on both alloantigen-induced DNA synthesis and PWM-stimulated immunoglobulin producton of autologous peripheral blood mononuclear cells. In contrast, T cells from cultures treated with CYA exhibited significantly less or no suppressor activity as determined in both indicator system. Finally, CYA abrogated the generation of cytotoxic T cells against EBV-infected autologous cells, whereas non-CYA -treated T cells killed the virus-transformed target cells. Both suppressor and cytotoxic T-cell functions are known to play an essential role in the control of EBV infection by limiting the continuous growth of the virus-infected cells. These results, therefore, stongly suggest that cyclosporin A promotes the outgrowth of EBV-infected cells by abrogating the T-cell responses to the Epstein-Barr virus.

HLA-DR antigens render interleukin-2-producer T lymphocytes sensitive to interleukin-1

Monoclonal anti-HLA-DR antibodies inhibited the production of interleukin-2 (IL-2) when added from the initiation of autologous (AMLR) and allogeneic (MLR) mixed lymphocyte reactions, but not 60 h later. The inhibitory activity of the anti-DR sera became apparent 8 h after initiation of the cultures and was maintained throughout the culture period. Interleukin-1 (IL-1) added to cultures carried out in the absence of the anti-DR antibodies significantly enhanced the production of IL-2, whereas addition of IL-1 to anti-DR-treated AMLR and MLR cultures did not restore or increase the synthesis of IL-2. However, when the anti-DR antibodies were added to IL-1-supplemented AMLR and MLR cultures 60 h or more after initiation of the reactions, the antiserum no longer inhibited the capacity of IL-1 to promote the synthesis of IL-2 or the production of IL-2. Finally, resting T cells were unresponsive to IL-1 and did not produce IL-2. It thus seemed that the anit-DR antibodies inhibited production of IL-2 in AMLR and MLR by rendering the IL-2 producer T cells unresponsive to IL-1. Cyclosporin-A, a drug that abrogates activation of T cells by blocking their receptors for HLA-DR antigens, also rendered IL-2 producer T cells unresponsive to IL-1 and abrogated the production of IL-2 in AMLR and MLR. Since resting T cells cells do not respond to IL-1 or produce IL-2, it is concluded that HLA-DR antigens of the stimulator cells participate in the production of IL-2 in AMLR and MLR by enabling the IL-2 producer T lymphocytes to respond to IL-1. Interleukin-1 promotes the production of IL-2 by IL-1-sensitive T cells. Once the IL-2-producer T cells become sensitive to IL-1, there is no further requirement for HLA-DR antigens.

Differences in immunoregulatory T cell circuits between diphenylhydantoin-related and spontaneously occurring systemic lupus erythematosus

We studied T cell surface markers, concanavalin A-induced, and spontaneously expanded suppressor cell function and the functions of postthymic precursor (Tar) cells in 3 patients with diphenylhydantoin (DPH)-related systemic lupus erythematosus (SLE). The findings were compared with those in 6 patients with spontaneously occurring SLE, 3 with active and 3 with inactive disease as well as with those in 3 normal volunteers. All 4 groups were age and sex matched. Findings were also compared to studies made in a group of 32 untreated idiopathic SLE patients and 32 normal controls. All T cell markers and immunoregulatory functions were normal in the DPH-treated SLE patients whereas all groups of patients with spontaneously occurring SLE had low numbers of t gamma cells, and Tar cells, and decreased concanavalin-A and spontaneously expended suppressor, human feedback inhibition and generation of suppression functions. Since consanguineous relatives of patients with spontaneously occurring SLE have been shown to have decreased suppressor cell function and patients with long-inactive spontaneous SLE continue to have defects in their T cell circuits, our findings may indicate that, in patients who develop SLE upon DPH intake the lupus diathesis uncovered by the drug probably resides in a site of immunoregulation different from that involved in spontaneously occurring lupus.

T cell growth factor abrogates concanavalin A-induced suppressor cell function

Concanavalin A (Con-A)-induced suppressor T cells were found to respond to T cell growth factor (TCGF) by proliferation. TCGF abrogated the suppressor activity exerted by these cells on phytohemagglutinin (PHA)- and alloantigen- induced lymphocyte proliferation and on pokeweed mitogen (PWM)-driven immunoglobulin secretion. The Con-A-activated suppressor T cells absorbed the TCGF activity, preincubation of these active suppressor cells with TCGF abolished their suppressor activity and addition of increasing numbers of Con-A-activated T cells reverted the abrogator,/ effect of TCGF. Altogether, these findings suggest that Con-A-induced suppressor T cells exert their function by decreasing the available levels of TCGF. Cyclosporin-A (CYA), which is known to inhibit the expression of receptors for TCGF on T cells, also inhibited the suppressor activity as determined in both indicator systems, namely PHA- or alloantigen-induced DNA synthesis and PWM-induced immunoglobulin synthesis. CYA made Con-A-treated T cells unresponsive to TCGF and unable to absorb the growth factor, supporting the notion that CYA inhibits the expression of TCGF receptors on T cells, a mechanism by which this drug seems to abrogate Con-A-induced suppressor T cell function.

Human postthymic precursor cells in health and disease. VII. Immunoregulatory circuits of the peripheral blood mononuclear cells from patients with progressive systemic sclerosis

The study of T cell subpopulations and their immunoregulatory circuits in 9 patients with progressive systemic sclerosis (PSS) and 9 age/sex matched controls showed: 1. Normal postthymic precursor autologous rosette-forming T cells (Tar cells). 2. Normal T cells with receptors for the Fc portion of IgG(Ty). 3. Decreased T cells with receptor for Fc portion of IgM(Tmu). 4. Normal function of postthymic precursors. 5. Normal Concanavalin-A-induced and spontaneously-expanded suppressor cell functions. 6. Abnormally increased T helper cell function. These findings suggest that the primary immunoregulatory aberration in PSS is at the level of Tmu cells and their helper function. Relationship between this T cell disturbance and fibroblast function may explain the pathogenesis of PSS.

Human post-thymic precursor cells in health and disease. III. Role of the autologous rosette-forming T cells in the generation of spontaneous killer cells in the autologous mixed lymphocyte reaction

Adult peripheral blood T lymphocytes activated in autologous mixed lymphocyte reactions (AMLR) exerted cytotoxicity on both phytohaemagglutinin-stimulated cells and Epstein-Barr virus-transformed cells. When autologous rosette-forming T cells were removed from total T lymphocytes, there was no generation of cytotoxicity. Re-addition of autologous rosette-forming T cells (Tar cells) to a population of T cells depleted of Tar cells restored the cytotoxic activity. Treatment of Tar cells with mitomycin C before their activation in AMLR caused loss of their capacity to give rise to killer cells. Furthermore, resting Tar cells did not show any cytotoxic activity as determined in the two different types of target cells used. Since Tar cells are able to differentiate into T gamma cells and since T gamma cells possess spontaneous cytotoxic activity, it is likely that Tar cells participate in the generation of spontaneous killer cells in AMLR as precursors of cytotoxic effector cells.

Cimetidine abrogates suppressor T cell function in vitro

Cimetidine increased the [3H] thymidine incorporation of normal human mononuclear cells in culture both when unstimulated or when under the stimulus of phytohemagglutinin or pokeweed mitogen (PWM). It also increased their supernatant immunoglobulin production under PWM stimulus. These effects were higher when the cells were preincubated with cimetidine than when it was added simultaneously. To determine if this effect of cimetidine reflects an abrogation of suppression we studied concanavalin-A-induced suppressor function of normal mononuclear cells using both [3H] thymidine incorporation and immunoglobulin synthesis as indicator systems and found that preincubation with cimetidine caused significant decrease in suppressor cell function in both systems.

Human postthymic precursor cells in health and disease. II. Their loss and dysfunction in systemic lupus erythematosus and their partial correction with serum thymic factor

We have recently described that human autologous rosette-forming (Tar) cells have the characteristics of postthymic precursor cells. Herein we report that we found circulating Tar cells significantly diminished in 32 patients with untreated systemic lupus erythematosus (SLE) as compared to 32 age/sex matched controls. Pretreatment of peripheral blood mononuclear cells (MNC) from SLE patients with serum from young normal adults or wtih serum thymic factors (FTS) increased their percentages of Tar cells significantly but reached near normal values in only 3 patients with inactive disease. Patients and normal subjects had similar percentages of Tar cells binding peanut-agglutinin. Characteristic functions of postthymic precursor cells are feedback inhibition and generation of suppressor cells which we studied in systems where we depleted or added Tar cells to Tmu and B cells, or MNC, respectively, using as indicators the production of immunoglobulins measured in culture supernatants or 3H-thymidine incorporation. We found both functions diminished in SLE patients despite using the presence of a qualitative as well as quantitative defect. In two SLE patients studied both of these functions corrected partially when their Tar cells were pretreated with FTS. In 20 SLE patients we studied Tgamma and Tmu cells as well as Concanavalin-A-induced, spontaneously-expanded suppression and found Concanavalin-A-induced, spontaneously-expanded suppressor function and Tgamma cells diminished. However only the reduction of Tgamma and of spontaneously-expanded suppressor function were found to relate to disease activity. On the other hand, Tmu cells were found to be similar in numbers in SLE patients and normal controls.

Human post-thymic precursor cells in health and disease. IX. Immunoregulatory T cell circuits in peripheral blood of patients with rheumatoid arthritis

We studied T cell subpopulations and their immunoregulatory circuits in the peripheral blood of 16 patients with rheumatoid arthritis (RA) who were receiving no medications that might interfere with the results. We found normal T cells with receptors for the Fc portion of IgG or IgM as well as autologous rosette-forming T cells (Tar cells), a subpopulation of T cells we have found to have the properties of human post-thymic precursors. We also found that peripheral blood cells of RA patients have normal concanavalin A-induced or spontaneously-expanded suppressor cell functions. Also normal were the characteristic functions of the Tar cells; feedback inhibition and the generation of suppression. The normal state of these T cell subpopulations and immunoregulatory circuits in the peripheral blood of patients with RA contrasts with their various abnormalities in other connective tissue diseases. This may either mean that the immunoregulatory aberration in RA involves primarily B cells, or, if it involves T cells, that it does so primarily in the synovial membrane.

Human post-thymic precursor cells in health and disease. I. Characterization of the autologous rosette-forming T cells as post-thymic precursors

Human autologous-rosette-forming T cells (Tar cells) have many of the characteristics of post-thymic precursor cells. Thus, they bind to sheep erythrocytes but have neither receptors for the Fc portion of IgG nor for that of IgM. They include a subpopulation that binds peanut agglutinin which suggests that they are immature and, as opposed to T cells with either receptors for the FC portion of IgM (T mu) or of IgG (T gamma), Tar cells adhere to nylon wool, another possible indicator of immaturity, as is their extreme sensitivity to hydrocortisone both in vitro and in vivo. There are more Tar cells in cord blood than in the peripheral blood of young adults and there are more Tar cells in the peripheral blood of young adults than in the peripheral blood of elderly subjects. By co-culturing T mu and B cells, or T mu, or Tar and B cells in the presence of pokeweek mitogen (PWM) we were able to determine that these cells cause feedback inhibition, a function considered characteristic of post-thymic precursors. In co-cultures in which we placed mononuclear cells (MNC) or MNC plus Tar cells, or MNC depleted of Tar cells or MNC depleted of Tar cells plus Tar cells stimulated with PWM, we determined that Tar cells play a role in the generation of suppression thereby confirming that human Tar cells are precursor cells. We also found that Tar cells proliferated and generated T gamma and T mu cells both spontaneously and in greater numbers, under the effect of serum thymic factor.

HLA-DR antigens induce proliferation and cytotoxicity of T cells against haptenated (TNP and FITC) self structures

Antisera directed against the heavy, the light, or reactive against the complex of both chains of HLA-DR antigens strongly inhibited proliferation of T cells induced by TNP- or FITC-labeled autologous cells when added at initiation of the cultures, but not 72 h later. T cells from cultures treated with the anti-DR sera were unresponsive to interleukin-2 (IL-2). Nonetheless, the anti-DR sera did not inhibit proliferation of T cells that had already acquired sensitivity to IL-2. The DR antibodies abrogated the synthesis of IL-2 induced by both TNP-and FITC-conjugated autologous cells. Treatment of TNP-and FITC-labeled autologous cell cultures with the four different types of anti-DR sera significantly inhibited the induction of cytotoxic T cells. However, DR antibodies added at the effector phase of cytotoxicity assays did not inhibit the cytotoxic activity. Effector T cells from cultures treated with the anti-DR sera were unresponsive to IL-2 and addition of IL-2 to these cultures did not restore the cytotoxic activity. In contrast, effector T cells from cultures performed in the absence of the anti-DR sera proliferated to Il-2 stimulation and addition of IL-2 to these cultures significantly increased the generation of killer cells specific for hapten-labeled self structures. From these results we concluded the following: (1) Both the heavy and the light chains of Dr antigens participate actively in the activation of T cells by rendering resting T cells sensitive to IL-2 and by inducing production of the growth factor in TNP-and FITC-conjugated autologous cell cultures. (2) The heavy and light chains of the DR antigens play an essential role in the induction of cytotoxic T cells specific for hapten-labeled self structures, most likely by enabling cytotoxic T cells to respond to Il-2 and by inducing the IL-2 producer T cells to synthesize the growth factor.

Role of individual chains of HLA-DR antigens in activation of T cells induced by alloantigens

The role of HLA-DR antigens in the activation of T cells in the allogeneic mixed lymphocyte reaction (MLR) was studied by using antibodies raised against the alpha, beta or the complex of both chains of the HLA-DR antigens. Antisera directed against the alpha or the beta chain strongly inhibited the T-cell proliferative response when added at the beginning of MLR cultures but not 72 h later. T cells from MLR cultures treated with either alpha-chain- or beta-chain-specific antibodies did not respond to interleukin-2 (IL-2) by proliferating, whereas T cells from non-anti-DR-treated cultures showed a proliferative response to IL-2-stimulation. However, neither the anti-alpha chain nor the anti-beta chain serum was able to inhibit continuous proliferation of already activated, IL-2-reactive T cells supported by IL-2. In MLR, OKT4+ but not OKT8+ lymphocytes synthesized IL-2. This function was abrogated by the alpha-chain-specific antibody but not by the anti-beta chain serum. Interleukin-1 (IL-1) did not reverse the inhibitory activity on IL-2 synthesis of the alpha-chain antibody, while IL-1 promoted the production of IL-2 in MLR cultures not exposed to the anti-DR sera. In addition, nonstimulated OKT4+ cells were unresponsive to IL-1 and did not produce IL-2. From these results, it is concluded that HLA-DR antigens participate actively in the activation of T cells by allogeneic non-T cells. Thus, both the alpha and beta chains of HLA-DR antigens render resting T cells sensitive to IL-2. In addition, the alpha but not the beta chain participates in the production of IL-2 by enabling OKT4+ lymphocytes to respond to IL-1 and subsequently to synthesize IL-2. Once T cells have acquired responsiveness to IL-2 and this growth factor has been produced there is no further requirement for HLA-DR antigens. Continuous proliferation and growth of IL-2-reactive T cells depends on the availability of interleukin-2.