Induction of T15-specific suppressor T cells in mice with the CBA/N defect by neonatal injection with anti-T15 idiotype antibody

Mice with the CBA/N defect (xid) are unresponsive to phosphorylcholine (PC), To determine whether idiotype-specific suppressor T cells can also be generated in these defective mice, defective (CBA/N X BALB/c)F1 male and nondefective (CBA/N X BALB/c)F1 female or (BALB/c X CBA/N)F1 male mice were neonatally injected with antibodies specific for the major idiotype of anti-PC antibody, i.e., anti-TEPC-15 idiotype (T15id) antibody. Suppressor cell activity was examined by co-culturing spleen cells from neonatally treated F1 mice with spleen cells of normal nondefective F1 mice in the presence of antigen. Spleen cells from defective (CBA/NM X BALB/c)F1 mice treated with anti-T15id antibody demonstrated a level of suppressor activity (greater than 83% suppression) comparable to that of similarly treated nondefective F1 mice. This suppression was specific for the T15id of anti-PC response, and a Lyt-1-2+-bearing T cell population appeared to be responsible for the active suppression. These suppressor T cells recognized T15 but not PC, based on a functional absorption test. These results indicate that the CBA/N defects, including the deficiency in the anti-PC response by B lymphocytes and a possible T cell defect, do not influence the generation of T15id-specific suppressor T cells by neonatal injection with anti-T15id antibody.     

Regulatory mechanism of reagin production in mice at the T cell level. I. Suggestive evidence for the generation of class specific PPD-reactive helper T cell population in Mycobacterium-primed cells.

Helper T cell activities specific for purified protein derivative (PPD) generated by immunization with Mycobacterium tuberculosis (Tbc) or PPD were investigated concerning adoptive IgE and IgG antibody responses. It is interesting that preferential triggering activity of IgG antibody response was observed when PPD-reactive cells from mice immunized with Tbc were used as a helper cell source. The selective triggering of IgG B cells by Tbc-primed cells was consistently observed using DNP-primed B cell populations from mice immunized with DNP-carrier conjugate in either ICFA or alum. T cell dependency of helper activity was demonstrated by the fact that treatment of Tbc-primed cells with anti-Thy 1 antiserum plus complement abolished their helper activity. We also demonstrated that purified T cell populations selectively triggerred IgG B cells. Selective triggering of IgG B lymphocytes by Tbc-primed T cells may not be due to the influence of suppressor T cells supposedly present in Tbc-primed cells since this selectivity was not affected by X-irradiation of Tbc-primed T cell populations which may inactivate suppressor T cells. Furthermore, passive transfer of Tbc-primed cells into normal recipient mice, the condition which may detect the suppressor T cell effect much more sensitively in IgE production, or preimmunization with Tbc 2 weeks before, did not suppress primary anti-DNP IgE antibody response to DNP-PPD. Thus, the observations presented here are favorable to the concept of the presence of IgG class-specific helper T lymphocytes. Furthermore, PPD-reactive T cells from mice immunized with PPD itself exerted their helper function for triggering B cells of both IgE and IgG classes. This may also indicate that some of the components associated with Tbc other than PPD might negatively affect the development of PPD-reactive helper T cells specific to the IgE class. The generation of such IgG-specific T cell activity in the presence of Tbc will be discussed in the light of the T cell population involved in the regulation of antibody responses of different immunoglobulin classes.     

Coexistence of antigen-specific and idiotype-specific suppressor T cells in mice injected neonatally with a mixture of antigen and anti-idiotype antibody

Specific tolerance to phosphorylcholine (PC) can be induced in BALB/c mice by neonatal injection with either pneumococcal C-polysaccharide (PnC) containing PC or anti-TEPC-15 idiotype (T15id) antibody which recognizes the predominant idiotype of anti-PC antibody of BALB/c mice. Suppressor T cells (Ts) induced after treatment with anti-T15id antibody react with the T15id and PnC-induced Ts cells appear to recognize PC. A brief incubation of anti-id-induced, T15id-specific Ts with PnC-induced, PC-reactive Ts resulted in complete cancellation of their suppressor functions. However, both types of Ts were present in mice neonatally injected with mixtures of PnC and anti-T15id antibody. Neutralization experiments using either PnC-induced or anti-id-induced suppressor T cells strongly suggest that only one of the Ts cell types is functionally dominant in those mice: most frequently, T15id-specific Ts cells. The suppressor function of the other population is detectable only when the predominant Ts cell population is removed by anti-id or monoclonal IgM anti-PC (SP45) plus complement. However, both suppressor activities are completely eliminated when one of the Ts populations is removed by adherence to either antigen or T15id. These results suggest that mice neonatally injected with a mixture of antigen and anti-id antibody possess both types of suppressor T cells, yet only one type is functionally dominant.     

Augmentation of auto-anti-idiotypic antibody production by hapten-reactive helper T lymphocytes

Augmented auto-anti-idiotypic antibody production was effectively achieved by immunization of mice with haptenated myeloma protein in the presence of hapten-reactive helper T lymphocytes. Hapten-reactive helper T-lymphocyte activities were raised in BALB/c mice by immunization with para-azobenzoate (PAB)-derived mouse gamma globulin (MGG) prepared by amidination reaction (PAB_im-MGG). Helper T cell activity was effectively enhanced by pretreatment of mice with a PAB-derived nonimmunogenic copolymer of D-glutamic acid and D-lysine (D-GL) (PAB-D-GL) 3 days before priming with PAB_im-MGG; PAB-D-GL is a potent tolerogen of both PAB-specific suppressor T lymphocytes and PAB-specific B cells. After induction of these enhanced PAB-reactive helper T lymphocytes, mice were immunized with PAB-coupled TEPC-15 myeloma protein (PAB_im-T-15), which was also prepared by amidination reaction. Mice immunized in this way manifested strikingly enhanced titers of auto-anti-idiotypic antibodies, specific for the T-15 idiotype, as compared to control mice which had not been preimmunized with PAB_im-MGG. The ability of PAB_im-MGG preimmunization to facilitate auto-anti-idiotypic antibody production was due to the activity of PAB-reactive helper T cells since PAB-specific B cells had been abolished by prior treatment with PAB-D-GL. The implications of this model for future studies on immunological engineering the analysis of idiotype network phenomena are discussed.     

Suppressor cell function of human granular lymphocytes identified by the HNK-1 (Leu 7) monoclonal antibody

The HNK-1 (Leu 7) differentiation antigen defines a subpopulation of human granular lymphocytes with natural killer (NK) and K cell function. In this study, we investigated whether HNK-1+ cells, identified with the monoclonal antibody and purified with a fluorescence-activated cell sorter (FACS), could function as suppressor cells. The results demonstrated that purified HNK-1+ cells efficiently suppressed both PWM-induced IgG production by B cells and T cell proliferation in mixed lymphocyte reactions (MLR). Manifestation of this suppressor cell activity required immune complex activation and was partially sensitive to 2000 rad irradiation. This suppressor cell activity was predominantly mediated by a subset of HNK-1+ cells that have previously been shown to have maximum NK function and lack expression of the E rosette (ER) receptor and T cell antigens (e.g., T3 and T8). Thus, HNK-1+ER- cells suppressed a MLR by an average 52%; HNK-1+ER+ were one-half as efficient, causing an average 23% suppression. For comparison, we also examined the characteristics of Leu 2a+ suppressor T lymphocytes. In contrast to HNK-1+ cells, unactivated Leu 2a+ cells suppressed both B and T cell responses. This suppressor activity was not augmented by immune complex activation and was absolutely radio-sensitive in PWM assays. HNK-1+ cells, especially the HNK+ER- subset, can therefore mediate suppressor cell function in addition to their spontaneous cytotoxic function. Furthermore, some of their suppressor cell properties are distinct from those attributed to other types of suppressor lymphocytes.     

Strain-dependence and cellular aspects of the acceleration of age-dependent shift in class-specific helper and suppressor activity in the thymus of MRL/Mp mice by the LPR gene

Previous studies of the immunoregulatory activity of thymocytes from SJL/J mice have shown loss of suppressor activity for the antibody response by 24 weeks of age with appearance of helper activity. At the same time, suppressor cells developed which inhibit the generation of cytotoxic T lymphocytes (CTL). We now show a similar pattern of helper and suppressor activity in MRL/Mp mice. Presence of the lpr/lpr genotype significantly accelerated the onset of these changes in thymocyte activity. A similar pattern of thymocyte activity was not detected in C57B1/6 mice. In aged MRL-lpr mice, evidence of increased suppressor cell activity for the CTL response could be demonstrated in spleen, and the suppressor was sensitive to treatment with anti-thy 1.2 + complement. The magnitude of the deficiency in the CTL response in MRL-lpr mice was greater than could be accounted for by suppressor cell activity alone. Measurement of the frequency of CTL precursors (CTLP), the yield of CTL per CTLP, and the ability to produce and to respond to interleukin 2 (IL-2) indicated that a drop in CTLP frequency, subnormal generation of IL-2, and probably an intrinsic defect in the responsiveness of MRL-lpr CTLP to IL-2 was contributing to the defective CTL response. We were not able to link suppressor T cells with reduced responsiveness to IL-2. Ageing involves different patterns of change in immunoregulatory T-cell subsets in different strains of mice, depending on their genetic constitution. The general implications of this conclusion for prediction of immune dysfunction with age in genetically distinct members of an outbred population are discussed.     

Functional analysis of mononuclear cells infiltrating into tumors. V. A. soluble factor involved in the regulation of cytotoxic/suppressor T cell infiltration into tumors

We have analyzed the mechanisms controlling the accumulation of cytotoxic/suppressor T lymphocytes in tumor tissues. We found that tumor-infiltrating helper/inducer T cells isolated from T-9 gliosarcoma-sensitized rats between 4 and 6 days after T-9 gliosarcoma inoculation produced a lymphocyte migration factor (LMF) during in vitro culture. Four peaks of LMF activity (A through D) were detected upon fractionation of LMF by using a Mono Q anion exchange column chromatography. Peak C exhibited the strongest activity among the four peaks of LMF. The action of peak C was chemotactic, but not chemokinetic. Peak C had an isoelectric point of 8.0 and a Mr of 26,000 Da. Only cytotoxic/suppressor T cells were found to be sensitive to peak C in vitro as well as in vivo. It is thus likely that peak C is responsible for the infiltration of cytotoxic/suppressor T cells into tumor tissues. The infiltration of lymphocytes into tumor tissues might also be regulated by the expression of lymphocyte sensitivity for LMF. The target molecule for LMF at 4 days may involve an asparagine-linked oligosaccharide.     

Biological effects of anti-idiotypic antibodies on lymphocyte function: I. Analysis of the effects on B lymphocytes of combining site and framework-directed anti-T-15 idiotypic antibodies

Anti-idiotypic antibodies against TEPC-15 myeloma protein (BALB/c origin) were raised in allogeneic animals by immunization of A/J mice with the myeloma protein. The antibody activities were fractionated into two specificities by TEPC-15 immunoadsorbent affinity columns by elution with free hapten (phosphorylcholine, PC), followed by elution with acidic buffer (glycine- HCl, pH 2.3). Idiotype binding analysis indicated that the fraction eluted with hapten could be inhibited in its binding to TEPC-15 by free hapten (i.e., binding site-directed anti-idiotypic antibody), whereas the acid-eluted fraction could not (i.e., framework-directed anti-idiotypic antibody). When analyzed for their biological activities on PC-specific B lymphocytes producing T-15 idiotype-bearing antibodies, both anti-idiotypic antibody fractions had similar suppressive effects on the in vitro production of antiphosphorylcholine antibody in culture.     

Demonstration of phosphorylcholine-specific IgE B cells in CBA/N mice.

CBA/N mice, which did not make anti-PC IgM or IgG antibody against PC-conjugated T-dependent or T-independent antigens, produced IgE antibody to PC-determinant when they were immunized with PC-KLH. PC-specificity of IgE antibody produced in CBA/N mice was determined by inhibition of PCA reaction with free PC-hapten or C-polysaccharide or by absorption of reaginic activity in the serum with C-polysaccharide. The presence of T15 idiotype on anti-PC IgE antibody produced in CBA/N x BALB/c F1 males also showed that anti-PC IgE antibody in defective mice was PC-specific. The results suggest that PC-specific B epsilon cells may belong to a subpopulation distinct from PC-specific precursors for IgM and IgG responses.     

T-T interactions in the induction of antigen-specific human suppressor T lymphocytes in vitro.

We intended to investigate whether the suppression of antigen-induced antibody responses in vitro in man by T suppressor cells required contact of T suppressor cells with target cells or whether this effect was mediated by factors released by T suppressor cells. To this end supernatants of antigen-induced T suppressor cells were tested (by a plaque forming cell assay) for their capacity to suppress antibody responses of autologous and allogeneic human peripheral blood lymphocytes. We have shown that supernatants of antigen-specific T suppressor cells, designated as TsF24: a) can suppress an antibody response of autologous but not allogeneic lymphocytes to the inducing antigen; b) are antigen-specific in their effect; and 3) are produced by radiosensitive T cells. Furthermore, the target of the factor is a radiosensitive T cell. These findings taken together indicate that, in the generation of T-effector suppressor cells in man, T-T interactions occur, and in addition, that cellfree factors may be involved in these interactions.     

Deficiencies in suppressor T cell activity seen in patients with active systemic lupus erythematosus are due to the dilution of normally functioning suppressor T cells by nonsuppressor T cells

Concanavalin A (Con A)-activated T lymphocytes from patients with active, but not inactive, systemic lupus erythematosus (SLE) failed to express normal suppressor activity, regardless of the phenotype of CD4+ or CD8+. Con A-activated CD4+ or CD8+ T lymphocytes from the SLE patients and from normal controls were further separated into two populations, using the autologous erythrocyte rosette technique. One population very rich in cells capable of forming rosettes with autologous erythrocytes from the active patients showed the same degree of suppressor activity, as did that from normal controls; the CD4+ or CD8+ population poor in autorosetting cells derived from Con A-activated T lymphocytes from both the controls and patients did not express suppressor activity. Moreover, when autorosetting T cells from the active patients and nonrosetting cells from the same patients were mixed at a normal ratio (4:6), normal suppressor activity could be restored. It was notable that the frequency of autorosette-forming cells was markedly reduced in the Con A-activated T lymphocytes from the active, but not inactive, SLE patients, regardless of the phenotype of CD4+ or CD8+. These findings indicate the presence of a normally functioning suppressor T cell population in patients with active SLE. It seems that the lack of suppressor T cell function in patients with active SLE is due to the dilution of a few normal suppressor T cells by large numbers of nonsuppressor T lymphocytes.     

The asymmetry in idiotype-isotype expression in the response to phosphocholine is due to divergence in the expressed repertoires of Lyb-5+ and Lyb-5- B cells

The X-linked CBA/N immune defect was used to investigate the roles of Lyb-5- and Lyb-5+ B cells in the memory response to PC-KLH (phosphocholine-conjugated keyhole limpet hemocyanin). (CBA/N X BALB/c)F1 (CB) male mice express the xid mutation and thereby lack the Lyb-5+ B cell subset, whereas their female littermates are normal and express both Lyb-5+ and Lyb-5- B cells. After priming with PC-conjugated hemocyanin (PC-Hy) in complete Freund's adjuvant, female B cells produce three phenotypic sets of PC-KLH-specific antibody. The first set (group I) is dominated by T15+, IgM, IgA, and IgG3, PC-specific antibodies. The second subset (group II) is specific for phenylphosphocholine (PPC), and is dominated by T15-, IgG1, and IgG2 antibodies. The third set (group III) recognizes an epitope(s) composed of both the PPC hapten and carrier determinants. PC-Hy-primed B cells from immune defective CB male mice produce the same number of IgG1 and IgG2 plaque-forming cells (PFC) as do PC-Hy-primed normal female cells, and these PFC are also predominantly T15- and PPC specific (group II). In addition, a significant amount of group III IgG1 and IgG2 antibody is observed in the immune defective male response. In contrast to female B cells, immune defective male B cells produce a low IgM, IgA, and IgG3 memory response that is not composed of PC-specific (group I) antibodies; in fact, most of these antibodies arise from group III precursors and are not inhibited by either PC or PPC. PC-specific antibodies usually represent less than 25% of the anti-PC-KLH response in immune defective mice; however, these PC-specific antibodies are predominantly T15-. These data suggest that the Lyb-5-B cells in both normal and immune defective mice produce the T15-, IgG1, and IgG2 antibodies that dominate the secondary immune response to PC-KLH, and that the Lyb-5+ B cells produce the T15+, IgM, IgA, and IgG3 portion of the secondary response in normal mice. This hypothesis was confirmed by priming normal mice with the R36a strain of Streptococcus pneumoniae or with PC-Hy in saline. These forms of PC-antigen prime only the Lyb-5+ B cell subset. The adoptive transfer of these two B cell sources results in an anti-PC-KLH response that is T15 dominant and totally PC inhibitable.(ABSTRACT TRUNCATED AT 400 WORDS)     

Generation of specific helper cells and suppressor cells in vitro for the IgE and IgG antibody responses.

Normal splenic lymphocytes from BDF1 mice were cultured on ovalbumin (OA)-bearing syngeneic peritoneal adherent cells for 5 days and their subsequent helper function was tested by an adoptive transfer technique. Lymphocytes harvested from the culture were mixed with DNP-KLH-primed spleen cells and transferred into irradiated syngeneic mice followed by challenge with DNP-OA. The results showed that the cultured lymphocytes has helper function for both IgE and IgG anti-DNP antibody responses. Depletion of mast cells and T cells in the peritoneal adherent cell preparations did not affect the generation of helper cells in the culture. The helper function of the cultured lymphocytes was abolished by the treatment with anti-theta antiserum and complement and was specific for ovalbumin. The OA-specific helper T cells were generated in vitro by the culture of a T cell-rich fraction of normal spleen on T cell-depleted OA-bearing peritoneal cells. If the normal splenic lymphocytes or T cell-rich fraction were cultured with 10 mug/ml of OA in the absence of macrophages, cultured lymphocytes lacked helper function. The transfer of splenic lymphocytes or splenic T cells cultured with soluble OA to normal non-irradiated mice, however, suppressed both IgG and IgE antibody responses of the recipients to subsequent immunization with DNP-OA. The suppressor cells were sensitive to anti-theta antiserum and complement and their activity was specific for OA. The cultured cells transferred into normal mice did not suppress anti-hapten antibody response to DNP-KLH. Normal lymphocytes cultured on OA-bearing macrophages and had helper function in adoptive transfer experiments failed to suppress antibody response of non-irradiated recipients to DNP-OA. The results indicate that OA-bearing macrophages primed T cells and generated helper T cells, whereas the culture of normal lymphocytes with soluble OA in the absence of macrophages generated suppressor T cells.     

Phytohemagglutinin-lnduced acquisition of T-cell surface markers by rat bone marrow precursor cells in the absence of the thymic microenvironment

Two monoclonal antibodies specific for different rat T-cell subpopulations, the anti-helper-T-cell antibody, W3/25, and the OX8 suppressor cell antibody were used to investigate lectin-stimulated T-lymphocyte differentiation of F-344 rat bone marrow cells in culture. Cytofluorometric analysis of freshly isolated lymphocytes from thymus and spleen revealed that these tissues contained both W3/25? and OX8-positive populations but differed with respect to the number of cells and receptor density distribution. By contrast, bone marrow-derived lymphocytes exhibited negligible W3/25? or OX8-associated fluorescence. However, several days after stimulation of bone marrow lymphocytes with phytohemagglutinin (PHA), cells appeared bearing these markers. Two-parameter histogram analysis of light scatter measurements with cell surface immunoflu-orescence indicated that this phenomenon represented the appearance of a new population of cells, presumably mature T cells, bearing an increased density of marker. These findings suggest an induction of differentiation of bone marrow T precursor cells by nonthymic factors (PHA) since lymphocytes lacking mature T-cell marker expression developed this characteristic after several days in culture.     

Contribution of Lyb 5+ and Lyb 5- B cells to the primary and secondary phosphocholine-specific antibody response

Due to a mutation on their X-chromosome, CBA/N mice lack the Lyb-5+ subset of B cells. The loss of this B cell subset results in a profound alteration in the immune response of these mice to the hapten phosphocholine (PC). Thus, when these mice are immunized with high doses of PC-KLH (200 micrograms) in CFA, they: 1) fail to produce IgM anti-PC antibodies; 2) produce little or no anti-PC antibody bearing the normally predominant T15-idiotype; and 3) produce IgG anti-PC antibodies only late in the primary response. In order to more fully delineate this defect in responsiveness to PC, the splenic focus assay was used to analyze Lyb-5- B cell precursors from both normal and immune defective mice. Lyb-5- cells were obtained from normal (CBA/N x DBA/2)F1 (CD) female spleens by treatment with anti-Lyb-5 serum and complement. These normal Lyb-5- cells and Lyb-5- cells from immune defective CD male mice were stimulated in vitro with either PC-Hy or TNP-Hy in the presence of Hy-primed T helper cells. The results demonstrate that primary Lyb-5- PC-specific B cells fail to respond in the splenic focus assay, while secondary Lyb-5- PC-specific precursors respond normally, and that both primary and secondary Lyb-5- TNP-specific precursors respond in the splenic focus assay. These data suggest that Lyb-5- PC-specific precursors must differentiate into memory cells before they can be activated to secrete antibody, and they also indicate that the Lyb-5- B cell subset may be composed of two subsets with different activation requirements.     

The inhibitory effect of T-2 toxin on tolerance induction of delayed-type hypersensitivity in mice.

Mice injected intravenously with 1 X 10(9) sheep red blood cells (SRBC) showed no delayed-type hypersensitivity (DTH) response to SRBC and were unresponsive to DTH induction by sc injection of an optimal dose of SRBC. However, when treated with T-2 toxin, a mycotoxin, 2 days after the iv injection, mice became to show significant DTH response and to be responsive to the DTH induction by the sc injection. When the spleen cells of the mice receiving the iv injection were transferred to unsensitized syngeneic recipients, the DTH response of the recipients to SRBC was suppressed. However, the suppressor activity of the spleen cells was decreased by T-2 toxin treatment. By the iv injection, cell population of the spleen was increased and that of the thymus decreased. In contrast, by T-2 toxin treatment 2 days after the iv injection, cell population of the spleen was not increased and that of the thymus was markedly decreased. The ratio of theta-bearing cells was increased in the spleen by the iv injection. However, such increase was not observed after the T-2 toxin treatment. The ratio of Ig-bearing cells in the spleen was not changed by the iv injection and the T-2 toxin treatment after the iv injection. T-2 toxin seems to interfere with generation of suppressor cells for the DTH response.     

Differential expression of ecto-5' nucleotidase activity by functionally and phenotypically distinct subpopulations of human Leu-2+/T8+ lymphocytes

Subsets of Leu-2+/T8+ cytotoxic/suppressor T lymphocytes were isolated by using various methods of purification and were investigated for expression of ecto-5' nucleotidase (5'NT) enzyme activity by radiochemical, cytochemical, and ultrastructural techniques. By using both the radiochemical and the cytochemical methods. T4-OKM1- cells displayed higher 5'NT activity in comparison with the entire T4- subpopulation. Analyses of the subpopulations of T4- (and predominantly Leu-2+) cells defined by the Leu-15 or Lyt-1 (9.3) monoclonal antibodies demonstrated that T4-Leu-15- and T4-Lyt-1+ cells displayed high 5'NT activity, whereas virtually no activity was present in T4-Leu-15+ and T4-Lyt-1-cells. At the ultrastructural level, the 5'NT reaction product was detected on the plasma membrane of a proportion of nongranular Leu-2+/T8+ lymphocytes, but no activity was found on cells with a granular lymphocyte (GL) morphology. 5'NT activity was also analyzed in peripheral blood mononuclear cells from one patient with expanded numbers of GL and two patients with GL leukemia. The enzymatic activity was significantly lower in these patients than in normal controls. This study provides new cytochemical evidence demonstrating the heterogeneity of Leu-2+/T8+ cells, and indicates that the population with the suppressor phenotype and function (Leu-15+/Lyt-1-, GL morphology) displays low or absent 5'NT activity, whereas the population composed of cytotoxic cell precursors (Leu-15-/Lyt-1+, nongranular morphology) has high 5'NT activity. Implications of these data for the interpretation of low 5'NT activity described in several immunodeficiency states and lymphoproliferative disorders are discussed.     

T-lymphocyte subset interactions in the cell-mediated immune response to Epstein-Barr virus

The T-lymphocyte subset interactions in the cell-mediated response to Epstein-Barr virus (EBV) were studied in an in vitro system in which the ability of T lymphocytes to inhibit outgrowth of autologous EBV-transformed B lymphocytes is assessed. Inhibition could be demonstrated within lymphocytes of both the T4 and T8 surface phenotypes. Outgrowth inhibition was observed more frequently when the effector T-cell population contained cells of both surface phenotypes. In blocking experiments the OKT3 antibody completely prevents development of outgrowth inhibitory activity; the OKT4 and OKT8 antibodies were less effective in interfering with outgrowth inhibitory function. Maximal blocking activity occurred when antibody addition occurred in the early phase of generation of suppressor function. Pharmacologically achievable concentrations of interferon-alpha restored outgrowth inhibitory activity after blocking with monoclonal antibody. EBV reactivation was easily demonstrable in a group of 10 renal allograft recipients who received OKT3 antibody for treatment of acute rejection. These studies suggest that the immunoregulatory control of proliferation of EBV-transformed B lymphocytes is complex, and involves a collaborative interaction of lymphocytes of both the T4 and T8 surface phenotypes.     

Biological expressions of lymphocyte activation. IV. Concanavalin A-activated suppressor cells in mouse mixed lymphocyte reactions.

Thymus-derived lymphocytes (T cells) from mouse spleen, activated in vitro or in vivo with concanavalin A (Con A), suppress proliferative responses of syngenic lymphocytes in mixed lymphocyte reactions (MLR). Replication in vitro was not required for expression of suppressor activity by Con A-activated cells and was blocked in MLR by treating suppressor cells with mitomycin C or irradiation. Kinetics of MLR responses and viability of cultures were not altered by addition of activated suppressor cells. The data are consistent with a direct inhibitory effect of suppressor T cells on antigen-induced DNA replication. These observations extend a model previously described for regulation of antibody synthesis by Con A-activated T cells to control of cell-mediated immune responses. This model should be particularly useful in further definition of regulatory T cell subpopulations, and in investigation of interactions and relationships between such populations.     

Active suppression of host-versus-graft reaction in pregnant mice. VIII. The uterine decidua-associated suppressor cell is distinct from decidual NK cells

The fetus resulting from allogeneic mating expresses a variety of antigens that may serve as targets for rejection by the maternal immune system. Accumulation of non-T suppressor cells into the uterine decidua of allopregnant mice may serve to prevent such rejection. It has been previously shown that the suppressor activity in decidua during the second half of murine pregnancy is predominantly associated with a population of small lymphocytes with cytoplasmic granules that lack T-cell markers and inhibit the generation of cytotoxic lymphocytes (CTL) against paternal alloantigens both in vitro and in vivo. Since natural killer cells (NK) also possess cytoplasmic granules and may regulate the murine immune response, we examined the hypothesis that the decidua-associated non-T suppressor cell may represent a regulatory type of NK cell. Similar to NK cells, the decidua-associated suppressor cell expressed FcR for IgG. Unlike NK cells, the decidua-associated suppressor cell proved resistant to treatment with anti-asialo GM1 + C'. Sedimentation velocity examination demonstrated that decidua-associated NK activity was associated with cell population with a modal sedimentation of 4 mm/hr that was larger than the decidua-associated suppressor population. Potent suppressor cell activity was also recovered from the decidua of NK deficient allopregnant bg/bg mice. Therefore, decidua-associated NK cells and suppressor cells represent two distinct populations.