Immune response to a syngeneic mammary adenocarcinoma. III. Development of memory and suppressor functions modulating cellular cytotoxicity.

Measurement of the development of cytolytic activity by mammary tumor primed or unprimed syngeneic spleen cells on in vitro monolayers of the 13762 rat mammary tumor operationally defined several subpopulations of lymphoid cells involved in the cytotoxic response. In vitro sensitization of cells from Fischer 344 animals injected 2 to 10 days earlier with 2 x 10(7) viable tumor cells always resulted in a higher and earlier lytic response than cells from non-inoculated animals. Adoptive transfer of the same in vivo primed cells for 5 days in irradiated syngeneic hosts removed any cytotoxic cells originally present but subsequent in vitro sensitization still resulted in a higher and earlier cytolytic response. We defined such cells as "memory" cells for cytotoxicity. Memory cells were radiosensitive and specific for the immunizing target cell. In contrast to cells from animals inoculated for 3 to 10 days, cells obtained 11 and 12 days after immunization had a lower response than unprimed cells on vitro sensitization. The anamnestic response could be restored either by culturing 12-day primed cells in vitro for 2 days without antigen or by adoptive transfer for 5 days into irradiated syngeneic rats. This suggests that another population of cells is present in spleen and suppresses the conversion of memory to cytotoxic cells. A more direct measurement of suppressor cell function was obtained by coincubating tumor-primed and unprimed cells on monolayers during in vitro sensitization. Cells from animals bearing tumors for 5 to 10 days always caused an increase in the response of the mixed lymphocyte groups, whereas 11- to 13-day tumor primed cells always caused a marked decrease in the cytolytic response. These results suggest the following interpretation of the kinetics of cell-mediated cytotoxicity to syngeneic tumor inoculation. Cytotoxic cells appear about 6 days after immunization, reach peak levels 2 days later, and then decrease rapidly. Memory cells are generated at a faster rate, reach peak levels before maximum cytolytic activity, but are then functionally inhibited from converting into differentiated cytotoxic cells by a new population of suppressor cells which reach peak activity about 12 days after immunization.     

Cooperation between mouse T-cell subpopulations in the cell-mediated response to a natural poxvirus pathogen.

Irradiated CBA anti-DBA/2 cells (10⁶ cells/culture) suppressed the production of effector cells in cultures containing 10⁷ unprimed CBA (responder) and 10⁶ irradiated DBA/2 (stimulator) spleen cells per culture. The suppressive element was cellular and suppression was specific for the stimulating antigen. The suppressive activity resided in the cytotoxic cell population in that both suppressive and cytotoxic activities were found in cells of the same size range, predominantly in T-cells, were produced in response to similar doses of stimulator antigen, and were produced with the same time course following establishment of first sensitization cultures. Eventual suppression correlated with the cytotoxic activity introduced into second sensitization cultures by suppressor cells. The short-term cytotoxic activity and suppressor activity were both highly radioresistant. These studies indicate that the suppressor cells formed in an in vitro mixed lymphocyte culture are cytotoxic to stimulator cells.     

Control of human B lymphocyte responsiveness: enhanced suppressor T cell activity after in vitro incubation.

Human peripheral blood mononuclear cells (PBM) lost the capacity to generate immunoglobulin-secreting cells (ISC) in response to pokeweed mitogen (PWM) after a period of preincubation in vitro. When fresh PBM were co-cultured with preincubated PBM their response to PWM was inhibited, indicating that enhanced suppressor activity developed in the aged PBM concomitant with the loss of PWM responsiveness. Suppressor cell activity of aged PBM was present within the T lymphocyte population. The suppressor T cell inhibited PWM responsiveness of autologous and homologous PBM to an equivalent degree. The action of the suppressor cell was abrogated by inhibitors of DNA synthesis or by hydrocortisone. A suppressor T cell population with similar characteristics was found in freshly prepared PBM before in vitro incubation. Expansion of this suppressor T cell population during preincubation required cell division. There was no change in the functional capability of the helper T cell population as a result of similar in vitro culture. These observations indicate that a T cell population capable of suppressing PWM-induced generation of ISC can be selectively expanded by in vitro incubation of normal human PBM without additional mitogenic stimulation. Moreover, these data emphasize that control of B lymphocyte differentiation involves a critical interrelationship between T lymphocyte subpopulations exerting both positive and negative influences.     

Pokeweed mitogen-induced immunoglobulin secretion by peripheral blood lymphocytes from patients with primary intracranial tumors. Characterization of T helper and B cell function

We have previously demonstrated that patients with primary malignant brain tumors have impaired in vivo and in vitro cell-mediated immunity. The purpose of the present research was to employ pokeweed mitogen (PWM)-induced secretion of immunoglobulin (Ig) by peripheral blood lymphocytes (PBL) to further investigate impaired lymphocyte function in these patients. The PWM response of PBL from normal individuals averaged 8384 plaque-forming cells (PFC) per 10(6) cells, whereas the response of PBL from patients averaged 1590 PFC/10(6). The decreased PWM response of PBL patients could not be improved by varying the number of PBL placed in culture or employing different concentrations of PWM. Co-culture experiments to detect the presence of suppressor cells in PBL and purified T cell preparations from patients demonstrated that enhanced suppressor cell activity was not evident. Next, experiments were performed to assess the T-helper cell activity present in purified T cell preparations obtained from patients. The results demonstrated that T cells from patients lacked the ability to provide adequate helper activity in the PWM response. Moreover, studies with monoclonal antibodies directed against T cell subsets revealed that PBL from patients have a reduced percentage of T-helper cells (40%) as compared with normal values (55%). In concert with T-helper cell anomalies, B cell function in these patients also is diminished. Thus, these observations indicate that a combined T-helper and B cell defect may contribute to the broad impairment of host immunocompetence observed in patients with primary gliomas.     

Thymus dependency of neonatal tolerance induction in the absence of detectable suppressor cells

Neonatal thymectomy prevents tolerance induction with bovine serum albumin (BSA) in Wistar Furth (WF) rats whose thymus-derived (T) cell deficit is reconstituted with adult nonadherent peripheral blood lymphocytes (PBL). Sham-thymectomized (STx) rats given PBL become tolerant. To establish whether the adult T cells become tolerant in STx rats, their carrier-reactivity was studied in a cooperative immune response following challenge with methylated BSA (mBSA). The results indicate that carrier-reactive cells, derived from PBL, do become tolerant of BSA in the presence, but not in the absence, of the thymus. To determine whether thymic function during tolerance induction is mediated by suppressor T cells, attempts were made to replace the thymus with various populations of thymocytes or lymphoid cells from neonatal or adult normal rats or neonatal BSA-injected rats. No cell population tried could substitute for the thymus during tolerance induction. In addition, it was found that BSA-tolerant rats with intact thymi do not contain either nonspecific suppressor cells whose activity can be boosted with mBSA or specific suppressor activity demonstrable on transfer to normal rats. Timed thymectomy experiments showed that the thymus is required for more than 2, but less than 5 to 7 days after tolerogen injection for significant tolerance induction. These results imply that the thymus itself is necessary for tolerance induction in a peripheral T-cell population and that its effect is not mediated by suppressor cells. It is suggested that peripheral T helper cells may periodically recirculate through the thymus, at least in young rats, and become tolerant of antigen complexed with Ia antigens in the thymic epithelium. Such a mechanism may be of great importance in the development of self-recognition.     

Hypersensitivity pneumonitis in nonhuman primates. I. Studies on the relationship of immunoregulation and disease activity

We investigated the relationship of immunoregulation to disease activity in a nonhuman primate model of pigeon breeder's disease. Two Macaca arctoides monkeys developed classical symptoms of hypersensitivity pneumonitis after sensitization and prolonged bronchial challenge, whereas 2 other monkeys remained asymptomatic after in vivo challenge. There were no differences in the percentages of T cells, B cells, monocytes, or FC gamma-bearing T cells between symptomatic and asymptomatic animals. Nonetheless, we found a population of concanavalin A-induced, pigeon serum- (PS) induced, and spontaneous T cells that functioned as suppressor cells in autologous in vitro co-cultures in asymptomatic animals that were missing or nonfunctional in symptomatic animals. Monocyte suppressors functioned in both groups. We used low-dose total body irradiation (TBI) to inactivate T suppressor cells. Fifteen radiation units of TBI caused no change in the physical activity, routine chemistries, or blood counts of the 4 animals. After TBI, however, the previously asymptomatic animals developed fever, tachypnea, and signs of pulmonary congestion after in vivo challenge with PS. There was no change in the response to challenge in the symptomatic group. This altered response to in vivo challenge in the previously asymptomatic group persisted for 2 wk after TBI. During this period the difference in vitro immunoregulatory activity between Con A-induced, PS-induced, and spontaneous T cells in symptomatic and asymptomatic animals disappeared. Monocyte suppressors, however, continued to function in both groups after TBI. These data suggest that the monkey is an appropriate model for studies of human HP and that T cell immunoregulation may be an important element in the pathogenesis and disease activity of HP.     

Lymphocyte function in experimental African trypanosomiasis. III. Loss of lymph node cell responsiveness

The relationship between immunosuppression and suppressor cell activity in the lymphoid organs of animals with experimental African trypanosomiasis has been examined further. In the present study we measure the primary in vitro PFC response to SRBC by spleen and lymph node cells from Trypanosoma rhodesiense infected or drug-cured C57BL/6 mice. Passive transfer experiments with this culture system tested for the presence or absence of suppressor cells. We demonstrate that infected mice exhibit immunosuppression in the spleen cell population several weeks before becoming suppressed at the level of the lymph node cell populations. Although suppressor cells are present in immunosuppressed spleen cell populations, suppression of lymph node cell responsiveness was not attributable to suppressor cells detectable withi, lymph nodes. After Berenil treatment of terminally infected mice immunocompetence was restored gradually, first to the lymph node cells and subsequently to the spleen cell population. Recovery of spleen cell responsiveness was attributable to the loss of detectable suppressor cell activity within spleens. These results demonstrate that there is anatomical restriction of the suppressor cell population to trypanosome-infected mouse spleen and that loss of immunocompetence in the lymph nodes may be due to factors unrelated to suppressor cell effects.     

BCG-induced suppressor cells. I. Demonstration of a macrophage-like suppressor cell that inhibits cytotoxic T cell generation in vitro.

Spleen cells obtained from mice 5 to 40 days after infection with viable BCG organisms (BCG-spleens) were found to be unresponsive in vitro to both mitogenic and alloantigenic stimuli. Moreover, suppressor cells could be demonstrated in the spleens from these infected animals. When spleen cells from BCG-infected mice were added to either syngeneic or allogeneic normal spleen cells, the mixtures neither proliferated nor developed cytotoxic activity when cultured with alloantigen or with concanavalin A (Con A). The development of unresponsiveness post-infection paralleled the onset of suppressive activity. Spleen cells obtained from mice given heat-killed BCG were neither suppressive nor unresponsive. The suppressive activity of BCG-spleen cells was associated with an adherent, phagocytic cell that lacked membrane-associated Thy-1 antigen. Removal of this cell by passage through nylon wool columns resulted in a cell population that was no longer capable of suppression and that responded normally to alloantigen and to Con A. It would thus appear that BCG infection results in the development of a "suppressor" macrophage-like cell population within the spleen. The role of this cell type in regulation of the immune response in BCG-infected animals is as yet undefined.     

Immunopotentiating effects of amphotericin B. II. Enhanced in vitro proliferative responses of murine lymphocytes.

Enhanced in vitro proliferative responses to DNBSO3 were seen in lymph node cells and spleen cells after in vivo sensitization of mice with DNFB plus AmB compared with mice primed with DNFB alone. The T cell proliferation in the nylon column nonadherent fraction for both groups was highly similar, and the enhanced lymph node cell proliferation with AmB was demonstrated to be in the nylon adherent population consisting of both T and B cells. These and earlier studies of immunopotentiation by AmB are consistent with a mechanism that depends on selective interaction of the polyene with a subset of T cells and a resultant impairment of the normally induced suppressor regulation that limits the magnitude and duration of immune responses.     

Suppression of pokeweed mitogen-stimulated immunoglobulin production in patients with rheumatoid arthritis after treatment with total lymphoid irradiation

Patients with intractable rheumatoid arthritis (RA) were treated with total lymphoid irradiation (TLI, 2000 rad). We previously reported long-lasting clinical improvement in this group associated with a persistent decrease in circulating Leu-3 (helper subset) T cells and marked impairment of in vitro lymphocyte function. In the present experiments, we studied the mechanisms underlying the decrease in pokeweed mitogen stimulated immunoglobulin (Ig) secretion observed after TLI. Peripheral blood mononuclear cells (PBL) from TLI-treated patients produced 10-fold less Ig (both IgM and IgG) in response to pokeweed mitogen than before radiotherapy. This decrease in Ig production was associated with the presence of suppressor cells in co-culture studies. By using responder cells obtained from normal individuals (allogeneic system), PBL from eight of 12 patients after TLI suppressed Ig synthesis by more than 50%. In contrast, PBL from the same patients before TLI failed to suppress Ig synthesis. Suppression by post-TLI PBL was also demonstrated in an autologous system by using responder cells cryopreserved before TLI. Again, only cells obtained after TLI were suppressive in four of seven patients. PBL with suppressive activity contained suppressor T cells, and the latter cells bore the Leu-2 surface antigen. In 50% of the patients studied, suppressor cells were also found in the non-T fraction and were adherent to plastic. Interestingly, the Leu-2+ cells from TLI-treated patients were no more potent on a cell per cell basis than purified Leu-2+ cells obtained before TLI. Additional experiments suggested that the suppression mediated by T cells after TLI is related to the increased ratio of Leu-2 to Leu-3 cells observed after radiotherapy.     

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.     

Regulation of cellular immune response against autologous human melanoma. II. Mechanism of induction and specificity of suppression

The cytotoxic immune response in the peripheral blood lymphocytes (PBL) against an autologous malignant melanoma cell line, PJ-M, was found to be down-regulated in in vitro co-culture (IVC) selectively by unfractionated resident lymph node lymphocytes (derived from a lymph node infiltrated with the PJ-M melanoma cells) and T4+ as well as T8+ fractions of the resident lymph node-derived lymphocytes. In this study, the mechanism involved in, and the specificities of, cytotoxic immune response in this autologous system were examined at population and clonal levels. Resident lymph node lymphocytes were isolated from both involved and uninvolved lymph nodes from the same patient. Resident lymphocytes from both sources regulated the generation of cytotoxic immune response when both types of resident lymph node lymphocytes were further sensitized against the PJ-M cells in IVC and were expanded in interleukin 2 (IL 2). An IL 2-dependent homogeneous lymphocyte line (I-10:1) bearing the phenotype of a helper T cell (T4+) and a T4+ clone (I-10.3) of the I-10:1 line, established by limiting dilution culture, also down-regulated the generation of cytotoxic immune effector cells in the PBL in IVC against the PJ-M targets. The IL 2-dependent T4+ inducer line I-10:1 generated a functionally differentiated T8+ suppressor population(s) that, in turn, could abrogate cytotoxic response in fresh PBL in IVC against PJ-M cells. The inducer line I-10:1 and its subclone I-10.3 suppressed the generation of cytotoxic effector cells in the PBL in IVC selectively against the autologous PJ-M cells. Generation of cytotoxic allo-response in IVC was unaffected by the inducer lines. These results provide further evidence for the involvement of the regulatory network in cytotoxic immune response in an autologous human tumor system, and suggest a potential explanation for cytotoxic unresponsiveness against autologous melanoma cells.     

In vitro generation of suppressor cell activity: suppression of in vitro induction if cell-mediated cytotoxicity.

It was observed that when normal mouse spleen cells were cultured alone in vitro (precultured) for 3 to 7 days, these cells lost the ability to generate cell-mediated cytotoxicity (CML) during subsequent in vitro sensitization with allogeneic spleen cells, trinitrophenyl (TNP)-modified syngeneic spleen cells, or syngeneic tumor cells. These precultured cells, which were themselves unable to generate CML, were also shown in mixing experiments to suppress, actively, the generation of CML by freshly explanted spleen cells. Suppression occurred at the sensitization phase of CML, and not at the effector level; supernatants from suppressive precultured cells were not suppressive. Suppression was totally abrogated by the treatment of spleen cells with a T cell-specific rabbit anti-mouse brain serum and complement (RalphaMB+C) either before or after preculturing, suggesting that a T cell eas essential both to the generation of suppressor activity and to its expression. Suppressor activity was entirely absent in precultured nylon wool column-nonadherent spleen cells, a T cell-enriched population containing most of the RalphaMB+C-sensitive cells in the spleen. Precultured nylon column-adherent cells (T cell-depleted) did have suppressive activity, and a mixture of nylon-adherent and nylon-non-adherent cells was a suppressive after preculture as the precultured unseparated spleen. Moreover, the ability of nylon-adherent spleen cells to generate suppressive activity during preculturing was abrogated by treatment with RalphaMB+C. Thus, the "spontaneous" generation of CML-suppressive activity was dependent upon a limited subpopulation of splenic T cells isolated in the nylon column-adherent fraction. The relationship of these data to a previously described synergy between subpopulations of normal spleen in the generation of CML is discussed, and the findings related to other suppressor systems described in the literature.     

Evaluation of intrauterine immune suppression during pregnancy in a species with epitheliochorial placentation

Cells capable of suppressing the immune response of PBL to the mitogen PHA are associated with the epitheliochorial placenta during normal first pregnancy in the pig. Because placentation in the pig is noninvasive, these suppressor cells are not associated with decidua. Cells with similar activity are also found between the implantation sites and in the uterus of pseudopregnant pigs, suggesting that fetal trophoblast is not essential for recruitment of intrauterine suppressor cells. Cell separation studies demonstrate that two independent populations of suppressor cells are present in the pig uterus on day 28 of gestation, as well as a population of PHA-responsive cells. The inability of unseparated porcine uterine cells to respond to PHA, plus the reconstitution of suppression in remixing experiments, demonstrate directly that a functional, putative T effector cell population is blocked within the uterus during normal mammalian pregnancy.     

Inhibition of specific immune responses by feeding protein antigens. IV. Evidence for tolerance and specific active suppression of cell-mediated immune responses to ovalbumin.

We studied the effect of a single intragastric administration of ovalbumin (OVA) on the subsequent development of OVA-specific cell-mediated immune (CMI) responses in BDF1 mice. In animals fed OVA 7 days before subcutaneous sensitization with OVA-CFA, we observed a concomitant dose-dependent decrease in both the humoral and CMI responses specific for OVA. The CMI tolerance was found to be antigen-specific when assayed in vivo by ear swelling or in vitro by an antigen-induced T cell proliferation assay because OVA-fed mice responded normally to sensitization with horse gamma-globulin. It was also shown that either spleen or lymph node cells, but not serum, from OVA-fed donors transferred suppression to normal recipients. The transfer was mediated by antigen-specific suppressor T cells (Ts) that appeared to inhibit the induction phase (afferent limb) of the CMI response, since the Ts were only effective when transferred before or shortly after the onset of sensitization.     

Interactions and quantitative analysis of immunoregulatory cells in the chicken thymus

Step-wise dilution of chicken thymus cell suspensions has been used to sequentially reveal suppressor, effector, and helper cells in these suspensions. The cells were tested either alone or in autologous mixture combinations with peripheral blood lymphocytes (PBL) as a source of effector cells. The assays studied were graft-vs-host reaction (GvHR) and mixed lymphocyte (MLR) reaction, spontaneous cellular cytotoxicity and antibody-dependent cell-mediated cytotoxicity, and mitogen responsiveness to Con A, PHA, and PWM. When tested alone, high numbers of thymus cells (1 X 10(7) gave weak or low responses, with the exception of GvHR, which was high. When this number of thymocytes was mixed with a strongly responding PBL effector population, there was marked suppression of the latter. Nonspecific crowding was excluded as a cause for the decreased responsiveness, and the data therefore demonstrated the presence of suppressor cells in the thymus. With gradual reduction of the thymus cell number in the mixtures, the suppressor activity was lost, but concomitant with this was the appearance of, or a gradual increase in, thymus effector cells giving good responses. Further dilutions of the thymus (to, e.g., 1 X 10(5) cells) depleted the suspension of effector cells, but helper cells capable of markedly amplifying the effector potential of PBL were revealed. The suppressor/helper function of the thymus was not only dependent on the absolute numbers of thymus cells present, but also on the degree of inherent responsiveness of the effector PBL. If the response of PBL alone was strong, a thymus suspension containing both helper and suppressor cells (e.g., 1 X 10(6) cells) caused suppression of the PBL; if the PBL alone were weak, this same thymus cell suspension caused enhancement. The outcome of an immune response is therefore dependent not only on the presence or absence of particular cell types, but also on the ratios between these cells. An imbalance in these ratios in vivo may underlie diseases of immunologic origin, e.g., autoimmunity.     

Tolerance and contact sensitivity to DNFB in mice. VI. Inhibition of afferent sensitivity by suppressor T cells in adoptive tolerance.

Tolerance in contact sensitivity to DNFB can be adoptively transferred to normal mice with lymph node cells from tolerant donors. This tolerance is antigen specific and is mediated by T cells, i.e., "suppressor" T cells. Experiments were carried out to investigate the mechanism(s) by which the suppressor T cells induce tolerance to DNFB contact sensitivity. The suppressor cells were effective only if they were present during the early stages of the afferent limb of sensitization. As measured by DNA synthesis, cell proliferation in the draining lymph nodes of recipients of suppressor cells was found to be significantly less than in control animals indicating that the suppressor cells acted, at least in part, by limiting or inhibiting DNFB-induced cell proliferation. This inhibition was shown to be antigen specific since the DNFB suppressor cells did not inhibit cell proliferation induced by oxazolone, an unrelated contact sensitizer. The ability to DNFB tolerant cells to block afferent sensitization pathways differs from the mechanism of tolerance to picryl chloride, reported by others, where efferent pathways are blocked.     

Lymphokine-activated suppressor (LAS) cells in patients with gastric carcinoma

Summary T-cell-growth-factor (TCGF) activated peripheral blood lymphocytes (PBL), cultured for 14 days, showed killer cell activities against natural-killer resistant Daudi cells in a 4 h ⁵¹Cr-release assay. However, the effector cells obtained from patients with nonresectable carcinoma exhibited very much lower cytotoxicity to tumor cells. To analyze the mechanism of depression, we have attempted to examine suppressor cell activities of the TCGF-activated PBL. The assay for the suppressor cell activities was made by in vitro inhibition of cell-mediated cytotoxicity by incubating radiolabeled target tumor cells with lymphokine-activated killer (LAK) cells and TCGF-activated PBL. LAK cells were induced by cultivation with recombinant interleukin-2. TCGF-activated PBL, obtained from four out of ten patients with resectable carcinoma and nine out of ten patients with nonresectable carcinoma, significantly suppressed the LAK cell activities. However, this suppression was not observed in TCGF-activated PBL from ten normal healthy control subjects. TCGF-activated PBL with immunosuppressive reactivity were named lymphokine-activated suppressor (LAS) cells. To investigate the phenotypic characterization of TCGF-activated PBL, the cells were analyzed by two-color flow cytometry. TCGF preferentially expanded CD8⁺CD11^– cells and decreased the growth of CD8⁺CD11⁺ cells in both normal healthy control subjects and gastric cancer (resectable and nonresectable) patients. Dominantly expressed CD8⁺CD11^– cells on TCGF-activated PBL in patients — especially those with nonresectable gastric carcinoma — showed strong LAS cell activity, irrespective of the presence of killer cell activities of CD8⁺CD11^– cells in TCGF-activated PBL from normal healthy control subjects. The results suggested the generation of CD8⁺CD11^– LAS cells from cancer patients, and revealed that CD8⁺CD11^– T-cells contained killer and/or suppressor cell function. In addition, it was found that the TCGF-activated PBL from gastric cancer patients were associated with an increased proportion of CD4⁺Leu8⁺, HLA-DR⁺CD8⁺ and HLA-DR⁺CD25⁺ cells.Abbreviations LAK lymphokine-activated killer - TCGF T-cell growth factor - PBL peripheral blood lymphocytes - rIL-2 recombinant interleukin-2 - LAS lymphokine-activated suppressor This study was supported by a grant-in-aid for scientific research (no. 62570307) from the Ministry of Education, Science and Culture, Japan     

The regulatory effect of histamine on the immune response: characterization of the cells involved

Any immunological response is the end result of the equilibrium between many positive and negative regulatory factors. It has been recently demonstrated that histamine receptor-bearing T lymphocytes could play a role in this regulation. This work aims to study the effects of different cell populations after incubation with histamine on the proliferative response of normal lymphocytes. The histamine-incubated peripheral blood lymphocytes (PBL) lower the proliferative response of normal cells toward mitogens (phytohemagglutinin, concanavalin A) and antigens (mixed lymphocyte culture). In order to precise the cell subpopulations involved in this suppression, PBL have been depleted of adherent cells and B and T lymphocytes have been purified by a standard rosette technique. The enriched B cells do not suppress the normal response but the suppressor activity of T cells, as well as adherent cell-depleted PBL, are significantly reduced compared to the one of PBL. The initial suppressor activity is restored by addition of 1% adherent cells (and not 5 or 10%) to adherent cell-depleted lymphocytes and 10% adherent cells (not 1 or 5%) to T-enriched population. These observations suggest a role for adherent cells in this regulation.     

An in vitro model for induction of immunologic unresponsiveness to turkey gamma-globulin in primed mouse spleen cells, II. Antigen-specific suppressor cells.

Unresponsiveness induced to turkey γ-globulin (TGG) in cultures of TGG-primed spleen cells by incubation with high concentrations of soluble TGG (sTGG) was shown to involve a state of active suppression. Upon transfer to secondary cultures of primed spleen cells stimulated with an optimal dose of TGG-conjugated erythrocytes, such tolerant spleen cells were able to actively inhibit a secondary plaque-forming cell response to TGG in these cultures. Almost complete inhibition was observed with a tolerant cell to primed cell ratio of as low as 0.1. The suppression was antigen specific in that tolerant spleen cells which were suppressive for the secondary TGG response were unable to inhibit a primary response to sheep erythrocytes. T cells were shown to be required for the suppressor effect, in that (i) suppressor activity could be removed by complement-mediated lysis with an anti-Thy 1.2 antiserum and (ii) suppressor activity was retained in the effluent fraction after passage of suppressor spleen cells over a nylon wool column. Induction of the T-cell suppressor activity was found to be associated with a loss of T-cell helper activity within the TGG-pulsed cell population. The presence of adherent cells was not required for induction of suppressor activity. Furthermore, the suppressor effect was found to be resistant to 1000 R of γ irradiation.