Human chorionic gonadotropin: effects of crude and purified preparations on lymphocyte responses to phytohemagglutinin and allogenenic stimulation.

The factors that prevent maternal immunologic rejection of the histoincompatible fetus are not understood. High levels of human chorionic gonadotropin (HCG) are present in the placenta, and several reports have noted suppresion of mitogen-induced lymphocyte transformation when cultures were supplemented with crude preparations of HCG. Purified HCG and multiple lots of crude HCG obtained from different suppliers were examined for their ability to suppress lymphocyte transformation produced by phytohemallutinin (PHA) or allogeneic stimulation. Crude preparations of HCG produced suppression of the lymphocyte stimulation induced by low doses of PHA, but the suppression could be overcome completely by increasing the PHA dose. The purified preparations of HCG produced no suppression of lymphocyte responses, even at the lower PHA dose. Purified HCG did not give a dose-related suppression of allogeneic lymphocyte responses, and crude lots of HCG gave highly variable results. One lot of crude HCG produced spontaneous stimulation of lymphocytes. Isoelectric focusing of HCG preparations demonstrated multiple bands, and lymphocyte suppression may be secondary to these additional unidentified proteins. The failure of pruified HCG to suppress lymphocyte responses makes it unlikely that the absence of maternal rejection of the fetus is due to high placental levels of HCG.     

Conditions affecting the immunosuppressive properties of human alpha-fetoprotein.

The hypothesis that alpha-fetoprotein (AFP) is immunosuppressive in vitro was tested with immunoabsorbent purified human cord AFP in human lymphocyte cultures. Albumins were purified identically from cord plasma and pooled adult plasma. No preparations were suppressive in phytohemagglutinin-stimulated cultures. Both AFP and human cord albumin (HCA) produced 50% suppression of allogeneic lymphocyte cultures at 50 to 100 microgram/ml final concentrations, whereas adult and commercial albumins were not suppressive. When AFP was eluted from the immunoabsorbent column in 0.15 M NaCl rather than the conventional 0.5 M NaCl, activity was greatly diminished or lost, but could be restored by dialysis against 0.5 M KCl. Previously, inactive lots of HCA also demonstrated the same phenomenon. It appears, therefore, that the immunosuppressive activity of AFP (and albumin) may depend both on its source and the procedure by which it is isolated. Whether analogous conditions occur in vivo is unknown at this time.     

Differential inhibition of human T-lymphocyte activation by maleimide probes

Cellular thiols are known to be involved in lymphocyte activation, differentiation, and growth. In theory, alkylation of selective cellular thiols could be used to regulate specific processes in the activation sequence by inactivating particular enzymes or structural proteins, although to date specific alkylating probes have not been reported. N-Ethylmaleimide (NEM) is a lipophilic sulfhydryl-alkylating agent that is known to block the in vitro proliferative response of T lymphocytes. NEM (10 microM) was found to be fully inhibitory in PHA, Con A, and MLC assays only when added prior to or simultaneously with the mitogens or allogeneic cells; the addition of NEM only 15 sec after stimulating the cells with PHA resulted in a loss of greater than 50% of the inhibitory activity. The addition of 50 microM 2-ME 10 min after treating the cells with NEM failed to block the inhibitory effect. NEM (10-20 microM) had no adverse effect on lymphocyte viability, but completely blocked lymphocyte agglutination in response to mitogens or allogeneic cells. The lymphocytes overcame the inhibitory effects of NEM after 48 hr in both the PHA and MLC experiments. Resumption of the proliferative response was associated with the onset of agglutination in the PHA assay. In experiments using various analogs of NEM, we noted that the presence of a nonpolar N-linked side group was necessary for inhibitory activity. Pretreatment of PBMC with NEM decreased the total cellular thiols by 50% and blocked proliferation by 99%, whereas N-hydroxymaleimide decreased the total cellular thiols by 38% but had no effect on the proliferative response. The additional 12% of the cellular thiols that react with NEM, but not NHM, account for the inhibitory effect of NEM on lymphocyte proliferation. These findings suggest that selective cellular thiols are critical for T-cell activation.     

Effect of LDL-In, a normal immunoregulatory human serum low density lipoprotein, on the interaction of macrophages with lymphocytes proliferating in response to mitogen and allogeneic stimulation.

The immunoregulatory properties of LDL-In, a normal species of human serum low density lipoprotein which suppresses indictive events involved in triggering of lymphoid cells by lectins and antigens, were analyzed in order to distinguish between a primary effect on macrophages and lymphocytes. LDL-In was found to be equally effective in suppression of the response of human lymphocytes to tpha at concentrations of lectin demonstrated to impart apparent macrophage-independence or macrophage-dependence to the culture system. Exposure of only the macrophages to LDL-In was shown to be without effect on subsequent in vitro lymphocyte responses to either PHA or allogeneic cells, whereas exposure of only the lymphocytes to LDL-In was fully effective. The cellular locus was further identified by demonstrating that the responder lymphocytes, but not the stimulator lymphocytes, were the target of the suppressive activity in mixed lymphocyte reactions. These data considered in conjunction with previous studies suggest that the primary untriggered lymphocyte is the most probable cellular target for the bioregulatory effects of LDL-In.     

Purine nucleoside modulation of functions of human lymphocytes.

The accumulation of endogenous substrates in patients with adenosine deaminase deficiency or purine nucleoside phosphorylase deficiency is believed to be responsible for the immunodeficiency observed in these patients. To identify the lymphocyte populations that are most susceptible to these substrates, we investigated the effect of their nucleoside analogs on a number of T and B cell functions of human lymphocytes. We found that tubercidin (Tub), 2-chloro 2'deoxyadenosine (2CldA), 2-fluoro adenine arabinoside-5'phosphate (FaraAMP), and 9-beta-D-arabinosyl guanine (AraGua) inhibited the proliferative responses of human peripheral blood mononuclear cells (PBMC) to polyclonal activators (PHA, OKT3 mab) or to allogeneic PBMC in mixed lymphocyte cultures (MLC). Addition of recombinant IL-2 from the beginning of the culture did not alter the inhibition by Tub of the proliferative responses of PBMC. These purine nucleoside analogs also inhibited the proliferative responses of purified human peripheral blood CD4+ and CD8+ T cells to PHA and of purified B cells to SAC. The concentrations of these nucleosides required to achieve a given degree of inhibition of proliferative responses of T lymphocyte subpopulations or B cells was similar, suggesting that these analogs do not exhibit any selectivity for these purified lymphocyte populations. Tub and FaraAMP, respectively, inhibited and enhanced, at the effector phase, both NK cytotoxicity and specific T cell-mediated cytotoxicity. In contrast to these findings, LAK cytotoxicity at the effector phase was not significantly inhibited by Tub, and was not enhanced by FaraAMP. Both analogs inhibited rIL-2-induced proliferative responses of PBMC, but did not affect the generation of LAK cytotoxicity (induction phase) against the K562 targets when added at the beginning of the culture. This suggests that DNA synthesis is not required for LAK cell induction. Both Tub and FaraAMP inhibited immunoglobulin production (IgG and IgM) by PBMC in the PWM-induced system. These results demonstrate that purine nucleoside analogs significantly inhibited a number of functions of human lymphocytes. Although selectivity for T lymphocyte subpopulations and B cells was not observed, a differential effect of Tub and FaraAMP on LAK cytotoxicity versus NK cytotoxicity and specific T cell cytotoxicity was found.     

Studies on the specificity of in vitro-induced lymphocytotoxicity to methylcholanthrene-induced fibrosarcoma cell lines

Cytotoxic effector lymphocytes were induced by in vitro immunization of lymph node and spleen cells from CS7B16(H2^b) and Balb/c(H2^d) mice to syngeneic or allogeneic methylcholanthrene-induced fibrosarcoma (MCAF) cell lines. The T cell-dependent cytotoxicity was specific to target cell lines to which the lymphocytes were immunized in vitro. Normal fibroblasts as stimulator cells did not induce lymphocytotoxicity to syngeneic MCAF cells or to normal syngeneic fibroblasts. The results indicate that the in vitro-immunized lymphocytes recognize individual specific tumor-associated antigens of the MCAF cells. In experiments in which the lymphocytes were immunized in vitro to allogeneic MCAF cells, cytotoxic reactions to alloantigens, but not to tumor-associated antigens, were detected. Incubation with phytohemagglutinin (PHA) during the sensitization period modified the specificity of the cell-mediated lysis of MCAF cells: Allogeneic as well as syngeneic target cells were destroyed by these effector cells. PHA induced a nonspecific cytotoxic effect which increased the specific lysis of target cells. The cytotoxicity of the in vitro-immunized lymphocytes was inhibited by incubation with membrane protein preparations from the syngeneic MCAF cell lines. In contrast to the specificity of the cytotoxic effect to the different syngeneic cell lines, the membrane extract of one individual syngeneic MCAF cell line was able to inhibit the lymphocytotoxicity to all other syngeneic cell lines. Membrane protein preparations from allogeneic MCAF cells or from normal syngeneic fibroblasts were not inhibitory. The in vitro-immunized cytotoxic lymphocytes did not impair the tumor growth in vivo as could be demonstrated by passive transfer of the lymphocytes in a Winn assay.     

Abnormalities of T cells isolated from mediastinal lymph nodes and peripheral blood of patients with lung carcinoma: deficit in PHA-induced expression of HLA class II antigens and in autologous mixed lymphocyte reactions

Summary A reduced percentage of T cells isolated from mediastinal lymph nodes and peripheral blood of patients with lung carcinoma acquired HLA Class II antigens following in vitro stimulation with PHA. Furthermore T cells were functionally abnormal in autologous and allogeneic mixed lymphocyte reactions (MLR). The immunoregulatory properties of HLA Class II antigens and autologous MLRs suggest that these abnormalities may affect the interaction of the host's immune system with tumor cells.     

In vitro allogeneic cytotoxicity in the solitary urochordate Styela clava.

Hemocytes from the solitary urochordate Styela clava can effect allogeneic cytotoxicity in vitro. Spectrophotometric and microscopic quantification of eosin-y dye exclusion revealed significantly greater frequencies of cell death in allogeneic hemocyte cultures when compared to autogeneic controls. This cytotoxic response was characterized by 1) transient activity such that specific cytotoxicity could be detected for only 4 hours of culture though continued specific killing may have been obscured by spontaneous cell death; 2) a necessity for cellular interaction demonstrated by the elimination of allogeneic cytotoxicity in the absence of cell contact; 3) killing of multiple targets by effector cells due to high levels of response at low allogeneic ratios; 4) insensitivity to altered temperature; 5) increased cytotoxicity in the absence of autologous plasma; 6) an absence of xenogeneic reactivity; 7) the presence of three hierarchical levels (low, intermediate, and high) of response. These data reflect events involved in the recognition of allogeneic cellular determinants resulting in specific cytotoxicity effected by immunocompetent cells. Such in vitro recognition and cytotoxic recognition and cytotoxic reactivity may be responsible for adaptive reactions caused by histoincompatibility in solitary tunicates.     

Cytotoxic effector cell function in organized gut-associated lymphoid tissue (GALT).

Lymphocytes from the organized gut-associated lymphoid tissues (GALT) of adult guinea pigs were examined for surface markers characteristic of T and B lymphocytes and for their capacity to function as effector cells in mitogen-induced cellular cytotoxicity (MICC) and antibody-dependent cellular cytotoxicity (ADCC) reactions. GALT lymphocytes formed rosettes with rabbit erythrocytes, a T-cell marker, and underwent proliferative responses in vitro in the presence of phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM). GALT lymphocytes were cytotoxic in vitro for erythrocyte and DBA mastocytoma targets in the presence of PHA. A population of GALT lymphocytes bound aggregated γ-globulin; however, they functioned poorly in ADCC reactions. Thus, organized GALT in the guinea pig contains lymphocytes capable of functioning in T-cell-dependent MICC reactions but either lacks the effector cell population which mediates ADCC or contains an effector cell which functions poorly in ADCC.     

Cell-mediated destruction of human leukemic cells by MHC identical lymphocytes: requirement for a proliferative trigger in vitro.

These experiments have investigated cellular mechanisms involved in the generation of cellular immune responses to human acute leukemic blasts. Because normal human lymphocytes are not able to recognize immunologically, in vitro, lymphocytes from MHC identical siblings, the present studies have examined the in vitro proliferative and cytotoxic responses of normal lymphocytes to MHC identical AML and ALL blasts. In those cases where acute leukemic cells were unable to induce a proliferative response by MHC identical lymphocytes, the generation of effective anti-leukemic cytotoxicity required the addition of unrelated stimulating cells to the sensitization culture. In contrast, leukemic blasts that induced a proliferative response by MHC identical lymphocytes were also able to stimulate anti-leukemic cytotoxicity. This could be augmented by the addition of unrelated stimulating cells to the sensitization culture. The specificity of anti-leukemic cell cytotoxicity was demonstrated in all instances by simultaneous testing of putative killer cells on 51Cr leukemic blasts as well as 51Cr-labeled MHC identical phytohemagglutinin blasts or normal lymphocytes. Simultaneous sensitization to MHC identical leukemic blasts and unrelated stimulating lymphocytes did not invariably generate anti-leukemic cytotoxicity even when allogeneic cytotoxicity was observed; the absence of demonstrable suppressor activity in these nonreactive combinations suggested that some individuals may be specifically immunoincompetent, and thereby unable to generate effective anti-leukemic CML.     

PHA-T cells in systemic lupus erythematosus and in rheumatoid arthritis: abnormalities in HLA class II antigen induction and in autologous mixed lymphocyte reactions

Analysis of T cells from patients with systemic lupus erythematosus (SLE) and with rheumatoid arthritis (RA) identified a deficit in the induction of HLA Class II antigens by PHA although the proliferative response was normal and in the [3H]thymidine incorporation in autologous mixed lymphocyte reactions (MLR) with PHA-T cells as stimulators. In RA these abnormalities were more marked in patients with active disease than in those in clinical remission. The deficit of autologous MLR with PHA-T cells was more marked than that of autologous MLR with non-T cells and of allogeneic MLR. Serum from patients with SLE and with RA did not display any detectable inhibitory activity on the induction of HLA Class II antigens by PHA, on the proliferative response of lymphocytes to PHA, on autologous MLR with PHA-T cells and with non-T cells as stimulators and on allogeneic MLR. These results suggest that the abnormalities we have identified reflect an intrinsic defect of T cells.     

Clonal and frequency analyses of tumor-infiltrating T lymphocytes from human solid tumors

A limiting dilution analysis (LDA) was used to assess the functional profiles of tumor-infiltrating lymphocytes (TIL) recovered from 15 human solid tumors. The microculture system applied in this study has been shown to allow virtually all normal peripheral blood T lymphocytes (PBL-T) to undergo clonal proliferation and was applied to obtain estimates of the frequency of both proliferating and cytolytic cells among the TIL population. A total of 624 microcultures proliferating in the presence of irradiated allogeneic spleen cells and interleukin 2 (IL 2) were expanded for clonal analysis. These TIL microcultures were assessed for surface antigen phenotype, IL 2 production (helper function) and for their cytolytic capabilities against the human erythroleukemic line K562 (natural killer (NK)-like activity) and P815, a mouse mastocytoma line, in the presence of phytohemagglutinin (PHA), i.e., lectin-dependent cell cytotoxicity (LDCC) which allows the detection of cytolytic activity irrespective of the antigenic specificity of the effector cells. Whenever feasible, cytolytic activity against autologous and allogeneic tumor cells was tested. LDA first demonstrated that the proliferative potential was decreased in T lymphocytes infiltrating human solid tumors (approximately 1 in 50 to 1 in 2 proliferating T lymphocyte precursors (PTL-P) in this series) as compared to normal PBL-T (1 in 2 to 1 in 1 PTL-P). The growth pattern in the titration cultures showed a remarkable agreement with the single-hit Poisson model implying that third party cells are unlikely to be involved in the reduced proliferative potential. Quantitative estimates of functional precursors showed that, in spite of reduced proliferative potential, cytolytic T lymphocyte precursors (CTL-P) against unknown antigens (LDCC-reactive) accounted for a considerable part of the microcultures in many cases. The precursor frequency of T lymphocytes with NK-like activity was usually low in situ (with the exception of glioma), whereas it was in the normal range in the patient's autologous PBL-T. In four evaluable cases, quantitative assessment showed that 1 in 200 to 1 in 1000 T lymphocytes from TIL was cytolytic against allogeneic tumor cells, which is in the range of alloreactive cytolytic T lymphocytes (CTL) generated in the mixed lymphocyte culture from normal PBL. Cytolytic activity against autologous target cells could not be quantitatively estimated but out of 88 clones from 4 patients, 3 clones originating from 2 glioma patients showed high lytic values against autologous tumor.(ABSTRACT TRUNCATED AT 400 WORDS)     

Fluorescence-activated cell sorting of human T and B lymphocytes. II. Identification of the cell type responsible for interferon production and cell proliferation in response to mitogens

We have employed the fluorescence-activated cell sorter to separate pure viable preparations of human T and enriched B lymphocytes. Using such preparations, we have demonstrated that both human T and B cells can respond to PHA and PWM in vitro in the presence of macrophages with proliferation and the production of interferon, a mediator of cellular immunity. However, selective T cell interferon production and proliferative response can be assessed at 3 days in culture; B cell interferon production and proliferative response is delayed to 5 and 7 days. T cells or T cell products are ineffective in inducing or accelerating B cell interferon or proliferative response at 3 days. The use of 3-day T cell interferon production as a new technique for the assessment of T cell effector function and competence is suggested.     

Studies on the specificity of in vitro induced lymphocytotoxicity to SV40-transformed fibroblasts.

Cytotoxic effector lymphocytes were induced by in vitro immunization of lymph node and spleen cells from AKR-mice (H-2k) and from BALB/c-mice (H-2d) to syngeneic SV40-transformed fibroblasts. The T cell-dependent cytotoxicity was specific for target cells expressing the same H2-specificity as the immunizing cells. Nontransformed fibroblasts as stimulator cells did not induce efficient cytotoxicity to transformed or nontransformed target cells. Incubation with phytohemagglutinin during the sensitization period modified the specificity of the T cell-mediated lysis of syngeneic SV40-transformed fibroblasts: allogeneic as well as syngeneic target cells were destroyed by these effector cells. However, the polyclonal stimulant activates preferentially cytotoxicity to H2-matched target cells. The in vitro generation of cytotoxic effector cells was restricted to living SV40-transformed fibroblasts as immunizing cells; it was not possible to immunize lymphocytes in the presence of membrane proteins prepared from the SV40-transformed cells. The cytotoxicity of the in vitro immunized lymphocytes was inhibited by incubation with membrane protein preparations from syngeneic or allogeneic SV40-transformed fibroblasts.     

Immunosuppressive activity of T cell clones generated from human T cells stimulated with autologous TPHA cells

T cell clones were generated from human T cells stimulated with autologous phytohemagglutinin (PHA)-activated T (TPHA) cells. Characterization of three T cell clones originated from donor SF and one from donor JM showed that they proliferated when stimulated with autologous TPHA cells, non-T cells, and peripheral blood mononuclear cells, but did not proliferate when stimulated with allogeneic TPHA cells, non-T cells, and mononuclear cells, with autologous and allogeneic resting T cells, and with PHA. These results in conjunction with the blocking of the proliferation by anti-histocompatibility leukocyte antigen class II monoclonal antibodies indicate that these class II antigens are involved in the proliferation of T cell clones stimulated with autologous lymphoid cells. The four T cell clones are cytotoxic neither to autologous lymphoid cells nor to a panel of cultured human cell lines. The four T cell clones display immunosuppressive activity, since they inhibit the proliferation of autologous and allogeneic cells stimulated with antigens and mitogens and the secretion of immunoglobulin by B cells stimulated with pokeweed mitogen in presence of T cells. Furthermore, the four T cell clones display differential inhibitory activity on the proliferation of cultured human cell lines. The immunosuppressive activity is species-specific, since the T cell clones do not inhibit the proliferation of murine cells. The suppression is mediated by a factor(s) with an apparent m.w. of 13,000 to 16,000. The suppressor activity is labile at alkaline pH and is lost following incubation with pronase (100 U/ml) for 30 min at 37 degrees C.     

Immunomodulation of human leukocytes by staphylococcal enterotoxin A: augmentation of natural killer cells and induction of suppressor cells

Staphylococcal enterotoxin A (SEA), a protein isolated from culture supernatants of Staphylococcus aureus, is a potent T-cell mitogen and an inducer of interferon-gamma (IFN-gamma). We report here that SEA exhibits a number of significant in vitro immunomodulatory functions. In vitro treatment of human peripheral blood monocyte-depleted lymphocytes with SEA resulted in significant augmentation of their natural killer cytotoxicity against target cells from hemopoietic (K562, Daudi) or solid (melanoma, lung, colon) human tumor cell lines. SEA was found to be more effective than interferons-alpha (natural or Escherichia coli-derived) in augmenting natural killer (NK) cytotoxicity of peripheral blood lymphocytes. Studies on the kinetics of the augmentation revealed a significant increase of NK within 3 hr of in vitro treatment with SEA at 37 degrees C. A neutralizing monoclonal antibody specific for human IFN-gamma did not affect the augmentation of natural killer cytotoxicity by SEA, suggesting that SEA augmented natural killer cytotoxicity primarily by a mechanism not involving induction of interferon-gamma. Furthermore, in vitro treatment with SEA resulted in significant augmentation of antibody-dependent cell-mediated cytotoxicity and of natural killer-like cytotoxicity, generated in mixed lymphocyte culture, against the K562 targets. Induction of suppressor cells to proliferative responses of autologous or allogeneic mononuclear cells to phytohemagglutinin (PHA) or to allogeneic cells in mixed lymphocyte culture was observed after in vitro treatment of peripheral blood mononuclear leukocytes with SEA for 24 or 48 hr at 37 degrees C. In addition, the presence of SEA in mixed lymphocyte cultures (MLC) resulted in significant inhibition of the generation of specific T-cell-mediated cytotoxicity in MLC. These results suggest that SEA, which may be involved in S. aureus infections and in treatment with extracorporeal perfusion systems over S. aureus columns, can regulate a number of significant lymphoid functions.     

Inhibitory activity of medium-dialyzed transfer factor on lymphocyte blastogenesis.

Human transfer factor was prepared from normal donors with marked skin reactivity against common microbial antigens by dialysis of lymphocyte extracts versus tissue culture medium (TFmd). Several batches of TFmd were tested for their ability to specifically increase the DNA synthesis of unsensitized lymphocytes in vitro in the presence of the corresponding antigens (PPD, SKSD, Candida, Thistoplasmin). No transfer or immunologic reactivity by TFmd was observed. There was, however, a significant unspecific inhibition by TFmd of lymphocyte cultures stimulated by antigens, PHA or allogeneic cells.     

Cyclosporine-induced tolerance in experimental organ transplantation. Evidence of diminished donor-specific cytotoxicity relative to donor-specific proliferative response

Alloreactivity of intragraft and peripheral blood lymphocytes from tolerant canine lung allograft recipients was examined. Tolerance was induced by variable periods of treatment with cyclosporine. Analysis of effector cells from lung allografts (obtained by bronchoalveolar lavage) revealed the absence of specific cytolytic T lymphocyte (CTL) activity and the presence of a low level of cytolytic activity detected in a lectin-dependent cell-mediated cytotoxicity assay. In contrast, high levels of specific CTL activity and lectin-dependent activity were detected in cell preparations from lung allografts undergoing rejection. Tolerant recipients retained normal ability to generate specific CTL activity to third party alloantigens in mixed lymphocyte cultures (MLC) but had diminished ability to generate CTL to donor alloantigens in recipient X donor MLC. Addition of exogenous interleukin 2 to these MLC was unable to restore donor-specific CTL activity. Lymphocytes from tolerant recipients were, however, capable of generating proliferative responses and lectin-dependent cytotoxicity on exposure to donor alloantigens in MLC. Evidence presented in this report suggests that the lectin-dependent cytolytic activity generated in these MLC is mediated by lymphokine-activated killer cells. Such cells are likely to be activated by interleukin 2 released in the proliferative response. The results support the proposal that the cyclosporine-induced tolerant state is characterized by the relative inability to respond against major histocompatibility complex class I antigens in contrast to class II antigens and/or minor histocompatibility antigens since MLC-induced CTL are directed, for the most part, against class I molecules.     

Cell-mediated immune response in human hepatic echinococcosis. Analysis of antigen-induced lymphoproliferation and NK activity

In vitro cellular immune responsiveness was studied in 25 patients undergoing surgery for hepatic hydatid disease and in 22 matched healthy controls. Proliferation of peripheral blood mononuclear cells (PBMC) induced by phytohaemagglutinin (PHA) was not statistically different in the two groups, while proliferation induced by antigenic preparations obtained from the human commensal microorganism Candida albicans was depressed in patients as compared to healthy subjects. Confirming previous data, antigen specific proliferative response to hydatid cyst fluids was greatly enhanced in patients as compared to controls (P less than 0.01). On the other hand, natural killer (NK) activity was significantly reduced (P less than 0.005). Both impairment of NK activity and lymphoproliferation induced by commensal microorganisms suggest that patients following the parasitic infection present a condition of relevant hyporesponsiveness in cell-mediated defence.     

Mixed lymphocyte reaction in mice genetically selected for high (Hi/PHA) or low (Lo/PHA) responsiveness to phytohemagglutinin.

Lymph node cells from Hi/PHA and Lo/PHA mice were evaluated for proliferative response after stimulation by allogeneic lymphocytes (MLR) originating from four inbred strains of different H-2 haplotype (C57B1/6, DBA/2, CBA, A). Reactivity to MLR and PHA were compared in these two lines and in the four inbred strains. The high and low responder status of Hi/PHA and Lo/PHA, as determined by T mitogens lymphocyte responsiveness, was also observed when one measured T responsiveness after MLR. Values obtained with the four inbred strains are included in the range of those measured in Hi/PHA and Lo/PHA cells when stimulated by PHA as well as by allogeneic cells. In contrast, when used as stimulator cells, Hi/PHA or Lo/PHA lymphocytes induce an equivalent proliferative response versus every responder inbred strain studied. These experiments support the hypothesis of a common genetic control of proliferative response following PHA or MLR stimulation. The genes implicated would be different from those coding for I region associated antigens.