The recognition specificity of a murine helper T cell for hemagglutinin of influenza virus A/PR/8/34

Human large granular lymphocytes (LGL), which are known to be responsible for natural killer (NK) cell activity, also produced a variety of lymphokines including interleukin 2 (IL 2), colony stimulating factor (CSF), and interferon (IFN) in response to phytohemagglutinin (PHA) or concanavalin A (Con A). Human peripheral blood LGL, which were purified by removal of monocytes adhering to plastic flasks and nylon columns, followed by separation on a discontinuous Percoll gradient, and additional treatment with anti-OKT3 and Leu-M1 plus complement, were more potent producers of these lymphokines than unseparated mononuclear cells (MNC), nylon column-eluted cells, or purified T lymphocytes. Moreover, IL 2 production by LGL could be further distinguished in that it was not enhanced by the addition of macrophages or macrophage-derived factor, i.e., IL 1, whereas addition of macrophages did potentiate IL 2 production by T lymphocytes. Further analysis of cells in the LGL population using various monoclonal antibodies revealed that removal of cells with OKT11 or AF-10, a monoclonal antibody against human HLA-DR antigen, decreased IL 2 production, whereas removal of OKT8+, OKM1+, Leu-M1+, or Leu-7+ cells led to enhanced IL 2 production. The LGL population is therefore heterogeneous and includes at least three functionally and phenotypically distinct subsets. An atypical T cell subset (OKT3-, Leu-1-, OKT11+) rather than the myeloid subset of LGL (Leu-M1+ or OKMI+) was the source of LGL-derived IL 2, whereas the latter subset and/or another subset of OKT8+ cells appear to regulate this IL 2 production. In addition to performing NK activity, LGL on a per cell basis seem to be more effective than T lymphocytes in producing lymphokines, namely, IL2, CSF, and IFN.     

Effector activity of OKT4+ and OKT8+ T-cell subsets in lectin-dependent cell-mediated cytotoxicity against adherent HEp-2 cells

The role of OKT4+ and OKT8+ T-cell subsets was studied in lectin-dependent cell-mediated cytotoxicity (LDCC) against adherent HEp-2 human epipharynx carcinoma target cells. LDCC was evaluated by detachment from the monolayer of [3H]thymidine prelabeled HEp-2 cells in a 24-hr assay with a concanavalin A (Con A) dose of 25 microgram/ml at effector:target cell ratios of 5:1, 25:1, and 50:1. Under these conditions but without Con A considerable natural cell-mediated cytotoxicity (NCMC) was not elicited; however, the cytotoxicity was significantly augmented in the presence of Con A (=LDCC) by sheep erythrocyte rosette-forming T lymphocytes and by both OKT4+ and OKT8+ T-cell fractions. LDCC activity by isolated OKT8+ T cells was superior to that by OKT4+ T cells and unfractionated T lymphocytes. By contrast, addition of either OKT4+ or OKT8+ T cells together with unfractionated T lymphocytes, or OKT4+ and OKT8+ T cells mixed at ratios of 1:1, 1:2, and 2:1, to target cells did not result in major differences in comparison of LDCC activities by these mixed effector cell populations with each other or with that by unfractionated T lymphocytes. Parallel studies were carried out to determine the effect of OKT4+ and OKT8+ T-cell subsets on the Con A-induced proliferation of peripheral blood mononuclear cells (PBMC). While OKT8+ T cells inhibited the mitogenic response to Con A, OKT4+ T lymphocytes had no major effect. A higher responsiveness of the OKT8+ to OKT4+ T-cell subset in LDCC to HEp-2 targets and in Con A-induced lymphocyte proliferation is suggested.     

Interleukin 2-mediated immune interferon (IFN-gamma) production by human T cells and T cell subsets

Human interleukin 2 (IL 2, or T cell growth factor), which was free of lectin and interferon activity (IFN), induced human peripheral T lymphocytes to produce immune IFN (IFN-gamma). In contrast, non-T cells and macrophages did not produce IFN-gamma in response to IL 2. IL 2 acted directly on unstimulated T cells to induce IFN-gamma production, and also acted in synergy with a suboptimal dose (2 micrograms/ml) of concanavalin A (Con A) to enhance IFN-gamma production. The IFN-gamma-inducing activity of partially purified IL 2 was absorbed along with the IL 2 activity by murine IL 2-dependent CT-6 cell line cells. This further supports the view that IFN-gamma-inducing activity is identical to IL 2. When T cells were separated further into helper/inducer T4+ and suppressor/cytotoxic T8+ subsets by negative selection with monoclonal antibody and complement, both T4+ and T8+-enriched cells produced significant levels of IFN-gamma in response to IL 2. Complete removal of macrophages from purified T lymphocyte populations by treatment of OKM1 plus complement consistently reduced IFN-gamma production in response to IL 2 to a limited degree; readdition of macrophages restored IFN-gamma production by both T cell subsets. This observation that IL 2 contributes to the production of IFN-gamma by human lymphocytes suggests that a cascade of lymphocyte-cell interactions participates in human immune responses.     

The mechanisms of inhibition of human IL 2 production. II. PGE2 induction of suppressor T lymphocytes

In vitro and in vivo experiments indicate that the production of interleukin 2 (IL 2) by T lymphocytes is critical for the development of the effector phase of immunity. Complex cellular interactions are involved for the induction of IL 2 production. We have shown in a previous study that in humans monocytes can transmit opposite signals to the IL 2-producing cells. In addition to the positive signal delivered through the release of interleukin 1, human monocytes can deliver a negative signal through the release of prostaglandin E2 (PGE2). This monokine, known to activate suppressor mechanisms in several systems, was shown to inhibit IL 2 production. The data presented in this paper show that this PGE2-dependent inhibition is strictly dependent upon the presence of radiosensitive T cells in the culture, suggesting that PGE2 induces the activation of suppressor T cells modulating IL 2 production. Kinetics experiments indicate that these suppressor cells are radiosensitive during their induction phase but become radioresistant after 18 hr of incubation in the presence of PGE2. Successful in vitro induction of suppressor cells by incubation of enriched T cells with PGE2 was decisive for the analysis of the phenomenon. The induced suppressors were capable of inhibiting IL 2 production by fresh autologous T cells as well as inhibiting PHA proliferative response by these cells. A quantitative evaluation of IL 2 receptors on PGE2-treated cells has indicated that this absorption capacity was similar to the capacity of PBL known to express a low number of IL 2 receptors, thus excluding a suppression via absorption or competition for IL 2. No detectable killing of IL 2-producing cells by PGE2-induced suppressors was observed. The OKT4 and OKT8 phenotype of suppressor cells was examined. T cells were purified at two stages of differentiation before or after induction by PGE2 in vitro treatment. We conclude from these experiments that PGE2 activates suppressor cells among precursors segregating predominantly with the OKT8 subset and fewer cells with the OKT4 subset. After differentiation, however, the suppressor cells segregate with the OKT8 subset only. Such results were obtained by using positive selection (cellular affinity columns) and negative selection (monoclonal antibodies plus complement).     

Both cloned interleukin 2 and purified interleukin 1 are required for optimal growth of purified L3T4+ and Lyt 2+ lymphocytes initiated by concanavalin A

Concanavalin A (Con A), cloned interleukin 2 (IL-2), purified interleukin 1 (IL-1) or two different crude preparations containing IL-1 activity alone, did not induce proliferation of rigorously accessory cell (AC)-depleted splenic L3T4+ or Lyt 2+ lymphocytes. Con A together with saturating concentrations of cloned IL-2 (100 U/ml) promoted less than 40% of the proliferative responses observed in AC-supplemented L3T4+ and Lyt 2+ T-cell cultures. The three preparations of IL-1 used supported minimal proliferation of Con A-treated purified L3T4+ or Lyt 2+ lymphocytes. However, all these IL-1 preparations promoted significant growth of the T-cell populations if AC (1%) were included in the cultures. Cloned IL-2 combined with purified IL-1 promoted proliferation of Con A-treated L3T4+ and Lyt 2+ lymphocytes achieving approximately 75% of the responses observed in AC-supplemented T-cell cultures. The additive effect of IL-1 was apparent in the presence of saturating concentrations of cloned IL-2. Finally, Con A alone induced a detectable number of both L3T4+ and Lyt 2+ lymphocytes to express IL-2 receptors as determined with the anti-mouse IL-2 receptor antibody 7D4 by immunofluorescence and FACS analysis. Purified IL-1 neither induced detectable number of L3T4+ or Lyt 2+ T cells to express IL-2 receptors nor increased the number of Con A-treated T cells bearing IL-2 receptors. We have interpreted these findings to indicate the following: Con A alone is sufficient to induce highly purified L3T4+ and Lyt 2+ lymphocytes to express IL-2 receptors. Cloned IL-2 and purified IL-1 are required for optimal growth of L3T4+ and Lyt 2+ lymphocytes and these cytokines together efficiently replace AC in growth of T cells initiated by Con A. IL-1 alone does not replace AC in Con A-induced activation of mouse T cells. IL-1 exerts potentiation on IL-2-driven growth of Con A-treated L3T4+ and Lyt 2+ lymphocytes. The additive activity of IL-1 on growth of normal T cells is not due to increased production of IL-2 in the cultures or induction of normal T cells to expression of IL-2 receptors by IL-1. We propose that IL-1 optimizes the action and/or interaction of IL-2 with its receptors on the T-cell membrane (by, i.e., increasing affinity of the IL-2 receptor for its ligand and/or stabilizing the IL-2 receptor).     

Characterization of T lymphocyte subpopulations responsible for deficient interleukin 2 activity in patients with systemic lupus erythematosus

Normal immunoregulation depends on a complex set of cellular interactions in which interleukin 2 (IL 2) appears to play an important role. We have examined the IL 2 activity in patients with systemic lupus erythematosus (SLE). IL 2 production by phytohemagglutinin (PHA)-stimulated T cells for 48 hr was measured by the ability of their culture fluid to induce proliferation of normal human T cells that had been activated for more than 20 days by PHA plus IL 2. To measure IL 2 responsiveness, T cells were blasted by preincubation with concanavalin A for 96 hr and stimulated for another 72 hr with lectin-free standard IL 2. SLE T cells failed to produce normal levels of IL 2 in vitro compared with normal control T cells. This failure resided in both OKT4+ and OKT8+ cells. Furthermore, the abnormality was due neither to soluble inhibitory factors produced by SLE T cells nor to active suppressor cells that might be induced by PHA-stimulation. Responsiveness to IL 2 of T cells from some, but not all, SLE patients was decreased significantly from that of normal controls. Absorption studies as well as studies with anti-Tac antibody demonstrated that the impaired responsiveness of T cells in the specific patients with SLE was due to inadequate expression of IL 2 receptors on the T cells upon activation. This defect was exclusively ascribed to the dysfunction of OKT4+, but not OKT8+, cells. The above defects in production of and responsiveness to IL 2 observed in patients with SLE were present at all times regardless of the disease activity or of corticosteroid therapy. Thus, the deficient IL 2 activity may be intrinsic to SLE lymphocytes and may contribute to impaired immunoregulation and to the development of SLE.     

Activation of resting T lymphocytes by anti-CD3 (T3) antibodies in the absence of monocytes

The antigen receptor molecules on human T lymphocytes are noncovalently associated on the cell surface with the CD3 (T3) molecular complex. Perturbation of this complex with anti-CD3 monoclonal antibodies induces T cell activation. Previous studies have demonstrated that this process requires the participation of monocytes. In the present report, we demonstrate that purified, resting (G0 phase) T cells incubated with monoclonal anti-CD3 antibodies proliferate in response to purified interleukin 2 (IL 2), in a lymphokine dose-dependent fashion. Anti-CD3 antibody or IL 2 alone did not trigger cell division. The effect was specific for anti-CD3 antibodies because monoclonal antibodies reactive with other surface molecules (OKT4, OKT8, L368) were inactive. Furthermore, the same phenomenon was observed when anti-CD3 antibody Leu-4 (IgG1) was incubated with cells of individuals whose monocytes cannot process antibodies of the IgG1 subclass (Leu-4 nonresponders). In addition, both F(ab')2 and Fab fragments of anti-CD3 antibody OKT3 were also capable of rendering T cells receptive to the IL 2 growth signal. These data indicate that neither monocytes nor CD3 receptor cross-linking are required absolutely for resting T cell activation, provided that IL 2 is supplied exogenously. T lymphocytes treated with anti-CD3 antibodies proliferated in response to both purified mitogen-induced and recombinant IL 2. Antibodies to the IL 2 receptor (anti-Tac) inhibited the proliferation. Thus, the most likely mechanism for anti-CD3 antibody-mediated triggering is induction of IL 2 receptors.     

Induction of suppressor cells to T- and B-cell proliferative responses and immunoglobulin production by monoclonal antibodies recognizing the CD3 T-cell differentiation antigen

Monoclonal antibodies (mAb's) recognizing the CD3 T-cell differentiation antigen induced the generation of suppressor cells. These cells inhibited (1) proliferative responses of human peripheral blood mononuclear cells (PBMC) to PHA and allogeneic cells in mixed leukocyte culture; (2) proliferative responses of purified E-rosette-negative cells to Staphylococcus aureus Cowans I; and (3) de novo immunoglobulin synthesis and secretion in the pokeweed mitogen (PWM)-induced differentiation system. Monoclonal antibodies recognizing other T-cell differentiation antigens (anti-Leu 2a, anti-Leu 3a, and anti-Leu 5) did not induce the generation of suppressor cells, even at very high antibody concentrations. Statistically significant differences were not observed in the ability of the OKT3 and anti-Leu 4 mAb's to induce suppressor cells. Monocytes were not required for the generation of anti-CD3-induced suppressor cells. F(ab')2 fragments of the OKT3 mAb's were equally effective when compared with intact antibody molecules in inducing suppressor cells, although they did not induce proliferative responses. Proliferation was not required for the induction of suppressor cells. Irradiation (2500 rad) of PBMC before incubation with the anti-CD3 mAb did not affect the generation of suppressor cells. Furthermore, anti-CD3-induced suppressor cells were radioresistant. Addition of recombinant IL-2 to the cultures of responding cells and suppressor cells did not reverse the suppression. In vitro treatment of anti-CD3-induced suppressor cells with either the OKT4 mAb plus complement or the OKT8 mAb plus complement partially decreased the suppression of proliferative responses of PBMC to PHA or allogeneic cells in mixed lymphocytes culture. However, treatment with both OKT4 and OKT8 mAb's plus complement or the OKT11 mAb plus complement completely abolished the suppression. These results suggest that the suppressor cells are of the T11+T4+T8- and T11+T4-T8+ phenotypes. In other experiments, T4+T8- and T8+T4- cells were isolated from PBMC treated for 48 hr with anti-CD3 mAbs. Both these two populations significantly inhibited proliferative responses of autologous PBMC to PHA and de novo immunoglobulin synthesis and secretion by mixtures of purified T4 and B cells from normal donors, in the PWM-induced differentiation system. These results demonstrate that anti-CD3-induced suppressor cells are of the T4 or T8 phenotype. Treatment of purified T4+T8- and T8+T4- cells with anti-CD3 mAb's resulted in the generation of suppressor cells, suggesting that the precursors of the anti-CD3-induced suppressor cells can belong to either of these two populations.(ABSTRACT TRUNCATED AT 400 WORDS)     

TPA, tumor promoter-induced suppression of immunoglobulin secretion in human blood lymphocytes

12-O-Tetradecanoylphorbol-13-acetate (TPA) modulates DNA synthesis and differentiation of normal and malignant human lymphoid cells. Using the reverse plaque forming assay and radioimmunoassay, we showed that nontoxic concentrations of TPA (5 to 10 ng/ml) inhibited Ig secretion of peripheral blood lymphocytes. This inhibition was dependent on T lymphocytes and not monocytes; TPA treatment of the B cell-enriched fraction slightly enhanced Ig secretion. Suppression was evident when the proportion of TPA-pretreated T lymphocytes exceeded 50%. TPA-induced suppressor cells were present in both OKT8+ (suppressor/cytotoxic) and OKT4+ ("helper/inducer") subpopulations. The suppression was diminished but not abolished by the irradiation of T lymphocytes. In addition, TPA treatment modulated the expression of OKT4 antigen, whereas the expression of OKT8, 9.6 (sheep erythrocyte receptors) and surface Ig remained unchanged. Modulation of OKT4 was energy dependent and was not blocked by a maximal saturation of TPA receptors at 4 degrees C. We postulate that TPA-induced suppression of Ig secretion is T cell dependent and is likely to be associated with proliferation and activation of OKT8+ and OKT4+ lymphocytes and the induction of OKT4+ suppressor cells.     

Mechanism of action of a suppressor-activating factor (SAF) produced by a human T cell line

We previously described a potent suppressor-activating factor (SAF) produced constitutively by a 6-thioguanine-resistant mutant of the human T cell line CEM. In the present study, we investigated the mechanism of action of SAF. After a brief (4- to 18-hr) exposure to SAF at 37 degrees C, T lymphocytes (either unseparated, or purified OKT4+ and OKT8+ subpopulations), but not B lymphocytes, suppressed allogeneic and syngeneic T cells in co-culture experiments, apparently via the release of a suppressor activity. The total T cell-released suppressor activity (TRSA) accumulated after 3 days culture post-treatment was about 100- to 500-fold higher than the original suppressor activity (SAF) added to trigger the release. Arresting protein or DNA synthesis, or even killing the cells did not affect the release of TRSA by T lymphocytes, but lowering the incubation temperature to 4 degrees C reduced it drastically. Pre-treatment of T lymphocytes with the metabolic inhibitor, sodium azide, or the adenylate cyclase stimulator, prostaglandin E2, or the addition of exogenous dibutyryl cAMP, all suppressed the release of TRSA. The presence of monoclonal antibody OKT3, but not OKT4 or OKT8, enhanced the release of TRSA. The presence of OKT11 blocked the release of SAF. The functional characteristics of TRSA appeared to be identical to those of SAF. However, unlike SAF, interaction of T lymphocytes with TRSA triggered only marginal enhancement of suppressor activity. In addition, the kinetics of the suppression mediated by SAF showed a much larger increment as a function of time than that mediated by TRSA. Taken together, the data suggest that SAF might represent an activated form of SAF, and that the continuous activation of SAF by lymphocytes in culture may account for its high potency in suppressing T cell proliferation in vitro.     

Characterization and partial purification of a specific interleukin 2 inhibitor

To investigate the mechanisms that regulate the action of interleukin 2 (IL 2) and possibly limit its activity, we screened supernatants of mouse spleen cell cultures which had been stimulated with concanavalin A (Con A) for their ability to inhibit IL 2-mediated proliferation of a cloned IL 2-dependent line. Inhibitory activities with m.w. of 10,000 to 12,000 and 60,000 to 80,000 daltons could be identified in supernatants of both L3T4+ and Ly-2+ T cells, but not in supernatants of Con A or lipopolysaccharide-stimulated B cells. Maximal inhibitory activity was observed after 3 to 4 days of stimulation, and this inhibitory activity could be overcome by increasing the stimulatory concentration of IL 2. When the factor was further purified by reverse-phase high pressure liquid chromatography, it eluted as a single peak with an m.w. of 11,000 to 12,000 daltons which inhibited IL 2- but not IL 3-dependent proliferation. The mechanisms by which this new lymphokine might play in the control of the clonal expansion of T lymphocytes are 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.     

A defect in the suppressor circuits among OKT4+ cell populations in patients with systemic lupus erythematosus occurs independently of a defect in the OKT8+ suppressor T cell function

The autologous mixed lymphocyte reaction (MLR) is thought to be part of a regulatory role of T cells on B cell function. OKT4+, but not OKT8+, cells can proliferate in response to autologous non-T cells. Moreover, the OKT4+ cell population activated early in the course of autologous MLR functioned as inducer cells for the differentiation of B cells, whereas later in the response, the activated OKT4+ cells were particularly enriched in suppressor cells. A part of the autologous MLR appears to be an important pathway for the activation of feedback suppression mechanisms among cells contained within the OKT4+ populations. Patients with systemic lupus erythematosus (SLE) were studied with regard to the following OKT4+ cell functions in vitro after activation in the autologous MLR: a) proliferative response, and b) helper and suppressor activities for differentiation of B cells. A marked reduction in the proliferative response of OKT4+ cells was observed in SLE patients. SLE OKT4+ cells activated in the autologous MLR could function as helper cells but could not exert any suppressor activity. This OKT4+ cell abnormality was present regardless of the disease activity, and occurred in the absence of autoantibodies including anti-T cell antibodies. Instead, SLE anti-T cell antibodies could preferentially eliminate cells bearing the OKT8+ phenotype characteristic of suppressor cells in populations of normal T cells. These results suggest that the defect in the suppressor circuits among OKT4+ cell populations is intrinsic to SLE lymphocytes and that the OKT8+ suppressor T cell defect is caused by antibodies produced by the B cells of SLE patients.     

Intracellular activation signal requirements for the induction of IL-2 responsiveness in resting T cell subsets in humans

Activation signal requirements for the induction of the IL-2 responsiveness in purified subsets of human resting T cells, T4+ or T8+, have been investigated under the monocyte-depleted conditions. Substantial levels of IL-2 responsiveness were induced in T8+ cells by lectin, Con A, mAb directed against the CD3 Ag, OKT3, Ca2+ ionophore, ionomycin or phorbol ester, PMA. In contrast, none of these stimuli was by itself sufficient for the induction of IL-2 responsiveness in the T4+ subset. The latter cells could, however, be induced to respond to IL-2 by combinations of PMA plus either of Con A, OKT3, or ionomycin (but not any combination of Con A, ionomycin, and OKT3). These data indicate that induction of IL-2 responsiveness in the resting T4+ subset is more complex, possibly requiring two intracellular activation signals, increase in the concentration of intracellular Ca2+ and activation of protein kinase C, whereas either signal may directly trigger IL-2 responsiveness in the resting T8+ cells. The data further suggest that under optimal conditions, growth of both resting T4+ and T8+ subsets may be independent of monocytes.     

Secretions of anti-myelin-associated glycoprotein antibodies by B cells from patients with neuropathy and nonmalignant monoclonal gammopathy

Four patients with peripheral neuropathy and nonmalignant monoclonal gammopathy with anti-myelin-associated glycoprotein (MAG) antibodies were studied to determine whether secretion of anti-MAG IgM antibodies by B cells was autonomous, or whether the monoclonal B cells were responsive to T cells. Secretion of anti-MAG IgM by isolated B cells was stimulated by the addition of increasing numbers of pokeweed mitogen (PWM)-activated autologous OKT4+ helper T cells in all four patients. Secretion of anti-MAG IgM by peripheral blood lymphocytes was dependent on the ratio of OKT4+ T helper cells to OKT8+ T suppressor/cytotoxic cells. In three patients with an OKT4+ to OKT8+ T-cell ratio of 2:1, PWM activation stimulated secretion of anti-MAG IgM; in one patient with an OKT4+ to OKT8+ ratio of 1:2, activation by PWM suppressed anti-MAG IgM secretion. These studies suggest that the monoclonal B cells that secrete anti-MAG IgM are responsive to regulatory T cells.     

Delineation of suppressor and helper activity within the OKT4-defined T lymphocyte subset in human newborns

Lymphocytes taken from the cord blood of newborns have active suppressor activity. Using in vitro PWM-stimulated cocultures, unfractionated T cells from newborns potently suppressed the expected immunoglobulin G (IgG) synthesis of their mothers' peripheral blood lymphocytes (PBL). Using positive and negative selection techniques, we characterized the active suppressor cell as expressing the OKT4+T8- phenotype. This cord blood lymphocyte subset suppressed maternal IgG synthesis after depletion of maternal suppressor cells, implicating the ability of newborn T cells to suppress directly rather than by inducing adult suppressor activity. Sublethal amounts (1500 rad) of gamma-irradiation fully abrogated the suppressor activity of cord blood T lymphocytes. Radioresistant cord T cells provided T cell help. Irradiation of cord OKT4+ and OKT8+ populations and their subsequent culture with maternal B cells determined that helper activity was a radioresistant subpopulation of the OKT4+ subset. These results indicate significant differences in the functional properties of T cell subsets from adults and newborns. Population studies determined that cord blood lymphocytes had a greater proportion of OKT4+ cells and lower proportion of OKT8+ cells than PBL from unrelated adults. The mothers tested had similar proportions of OKT4+ cells as their babies, and these levels are significantly higher than those of unrelated adults.     

A monoclonal antibody reactive with the human cytotoxic/suppressor T cell subset previously defined by a heteroantiserum termed TH2

A hybridoma-secreting monoclonal antibody was produced from the spleen cells of a mouse immunized with human thymocytes. This hybridoma antibody, termed OKT5, was reactive by indirect immunofluorescence with 80% of human thymocytes but only 20% of peripheral blood T cells. Moreover, OKT5 was unreactive with normal B cells, null cells, and macrophages at any dilution tested. A similar pattern of reactivity was seen with an equine antiserum to human thymocytes termed anti-TH2. Fluorescence-activated cell sorting demonstrated that the OKT5 antibody reactivity on peripheral T cells was restricted to the majority of the previously defined TH2+ subpopulation. In functional studies, the OKT5+ subset, like the TH2+ subset, proliferated well to the mitogen Con A and to alloantigens, and contained cytotoxic effector cells after sensitization in MLC, and suppressor effector cells after activation with Con A. In addition, like the TH2+ T cell, the OKT+ T cell was virtually unresponsive to soluble antigen. Thus, the OKT5 monoclonal antibody is reactive with the cytotoxic/suppressor T cell subset. OKT5 should provide an important probe to assess the status of suppressor cells in human disease.     

The murine IL 2 receptor. III. Cellular requirements for the induction of IL 2 receptor expression on T cell subpopulations

The accessory cell requirements for the induction of the IL 2 receptor by the lectin Con A on murine T cell subsets were directly assayed with anti-IL 2 receptor monoclonal antibodies. Substantial levels of IL 2 receptor expression were induced on T lymphocytes of the MHC class I-restricted, suppressor/cytotoxic phenotype (L3T4-, Ly-2+) in the presence and absence of accessory cells. In contrast, high levels of IL 2 receptor expression could only be induced on T cells of the MHC class II-restricted, helper/inducer phenotype (L3T4+, LY-2-) in the presence, but not in the absence, of accessory cells. Ia- cells such as the P388D1 macrophage line or cultured fibroblasts (DAP X 3) were as efficient as the Ia+ B cell hybridoma LB in providing accessory cell function for the L3T4+, Ly-2- subset. PMA, but not purified human IL 1, could substitute for accessory cells for both IL 2 receptor expression and IL 2 secretion by the L3T4+, Ly-2- subset. These data suggest that IL 2 receptor induction on the L3T4+, Ly-2- subset is complex, possibly requiring a T cell-accessory cell interaction, whereas the lectin may directly trigger IL 2 receptor expression on L3T4-, Ly-2+ T cells.     

Expression of interleukin 1 receptors on human peripheral T cells

The expression of interleukin 1 receptors (IL 1R) on human peripheral T cells was studied by the binding assay with 125I-labeled recombinant human interleukin 1 (IL 1) alpha and IL 1 beta and by the flow cytofluorometry with the fluorescein isothiocyanate (FITC)-conjugated IL 1 alpha. Peripheral blood lymphocytes expressed only few IL 1R without any stimulations. When they were stimulated with concanavalin A (Con A), IL 1R-positive cells began to increase by 4 hr, reached the maximum level at 48 hr, and then gradually decreased. The kinetics of the expression of IL 1 alpha R and IL 1 beta R showed the same pattern. Furthermore the binding of 125I-labeled IL 1 alpha to IL 1R on T cells was inhibited by the addition of either cold IL 1 alpha or IL beta, but not by interleukin 2 or interferons. The similar results were observed in the binding of 125I-labeled IL 1 beta. These results suggest that IL 1R on human peripheral T cells reactive for IL 1 alpha and IL 1 beta were identical. By Scatchard plot analysis, the numbers of IL 1R were estimated as 40 and 350 molecules per cell before and after Con A stimulation, respectively, and their Kd values were 3.1 X 10(-10) M and 2.8 X 10(-10) M. When purified T cells alone were stimulated with Con A, IL 1R were only marginally expressed. However, by the addition of monocytes, IL 1R were expressed on T cells in a dose-dependent manner. The maximum response was induced in the presence of 10% monocytes. The maximum IL 1R-positive T cells were approximately 30% by the detection of the flow cytofluorometry with FITC-conjugated IL 1 alpha. This enhancing activity of IL 1R expression on T cells by monocytes was inhibited by the addition of an anti-HLA-DR antibody or by the treatment of monocytes with the anti-HLA-DR antibody and complement. Furthermore T cell proliferative responses induced with IL 1 and Con A were also enhanced by the addition of HLA-DR-positive monocytes. These results suggest that IL 1R are expressed as the result of monocyte-T cell interaction in the early stage of T cell activation, and the expression of IL 1R on T cells and the responsiveness of T cells for IL 1 require the accessory function of HLA-DR-positive monocytes.     

Distinct classes of human T-cell activation antigens

The characterization of three groups of antigens expressed by activated human T lymphocytes and detected by monoclonal antibodies is reported. Antigens defined by OKT19, OKT21, and OKT22 do not appear on in vitro activated T cells until increases in DNA synthesis become apparent and are not detected on most Interleukin 2 (IL-2)-independent cell lines and normal peripheral blood lymphocytes, monocytes, and granulocytes. Cell surface molecules reactive with the monoclonal antibodies OKT23 and OKT24 are displayed prior to any notable increase in DNA synthesis and are present on IL-2 independent cell lines, irrespective of lineage. T23 and T24 do not appear on peripheral blood cells and their distribution more closely resembles that of the T9 antigen (the receptor for transferrin) than antigens of the other groups. The third group of antigens, T14 and T20, have been classified as "early" antigens relative to DNA synthesis. They are expressed by distinct populations of normal lymphoid cells as well as by some IL-2-independent cell lines. Display of each group of activation antigens on T lymphocytes can be induced by either phytohemagglutinin, purified protein derivative from tuberculin, or allogeneic non-T cells, is not restricted to the OKT4+ or OKT8+ subsets, and is predominant on cells exhibiting the light-scattering properties of blast cells. The relative lack of expression of these antigens among normal peripheral blood cells make them attractive candidates for identifying changes in the status of immune activation.