The role of self-Ia antigens in the murine mixed lymphocyte response

Production of IL2 and IL3 in syngeneic mixed lymphocyte reactions of BALB/c mice are elevated during a period of moderate dietary protein deficiency

The mixed lymphocyte reaction (MLR) is a model of T cell responsiveness to antigenic peptides complexed with major histocompatibility (MHC) proteins on antigen presenting cells (APC). Since dietary protein deficiencies alter T cell development, syngeneic and allogeneic MLR were investigated in mice fed a low protein 4% casein (4Ca) or control 20% casein (20Ca) diet. Proliferation of splenic lymphocyte populations from BALB/c mice fed 4Ca was increased during syngeneic and allogeneic MLR compared with lymphocytes from mice fed 20Ca. Increased proliferation was accompanied by significantly higher production of IL2 and IL3 during syngeneic, but not allogeneic MLR. To determine the influence of autologous B cells on IL2 and IL3 production during MLR, lymphocyte populations of mice fed 4Ca or 20Ca were depleted of B cells. Splenic lymphocyte populations of mice fed 4Ca that were depleted of B cells did not exhibit increased IL2 or IL3 production during syngeneic or allogeneic MLR. Splenic APc of mice given 4Ca caused greater proliferation during MLR. However, APC of 4Ca mice did not cause greater IL2 or IL3 production. Similarly neither IgM-B cells nor macrophage from mice fed 4Ca induced elevated IL2 or IL3 production during syngeneic or allogeneic MLR. A dichotomy appeared in that 4Ca-APC were able to induce higher T cell proliferation but not cytokine production compared with 20Ca-APC. The enhancement of T cell responsiveness to Class II MHC determinants on APC during moderate protein deficiency appears to require both T and B cells from mice fed the deficient diet.

T cell responses to ovarian tumor vaccines: identification and significance for future immunotherapy

The cellular immune responses to ovarian cancer patients treated with viral oncolysates (VO) ovarian tumor vaccines to vaccines are described. CD3+ cells proliferated after stimulation with the tumor vaccines in a dose-dependent manner. The proliferation of CD3+ cells stimulated with the tumor vaccine was blocked by anti-HLA-DR monoclonal antibody and anti-CD4 mAb indicating that CD3+ CD4+ cells from the blood of the patients treated with VO recognize tumor derived determinants in conjunction with MHC class II antigens. The regulatory activity of the T cells collected after VO treatment was assayed by co-cultivation with PBMC collected before VO treatment. These cells demonstrated increased helper activity for immunoglobin production by cells collected before vaccination and secreted IL-2 in response to stimulation by vaccine. Finally, when biochemical fractionation of the components of VO was attempted, PBMC from VO treated patients responded by proliferation to several fractions suggesting that they recognize multiple epitopes in the ovarian tumor vaccine. Therefore, these data provide novel evidence for the involvement of the T cells in response to ovarian tumor vaccines.

Enhancement of human T lymphocyte function by prothymosin alpha: increased production of interleukin-2 and expression of interleukin-2 receptors in normal human peripheral blood T lymphocytes

The in vitro incubation of phytohemagglutinin (PHA)- or alloantigen-stimulated peripheral blood T cells with prothymosin alpha (ProT alpha) resulted in a marked and reproducible increase in the production of interleukin-2 (IL-2). Incubation of T cells with ProT alpha, in the absence of PHA or alloantigen, failed to induce any production of IL-2. ProT alpha by itself did not exert any IL-2 activity. Finally, ProT alpha was shown to increase the expression of IL-2 receptors on phytohemagglutinin- or alloantigen-activated T cells. These data provide the basis for understanding the in vitro immunoenhancing effects of ProT alpha in cellular immune systems.

Peripheral but not thymic T cells participate in an autoreactive T cell network

Splenic T cells proliferate in response to the anti-I-Ab reactive T cell hybridoma T1.203 in an H-2-restricted but MHC antigen-independent manner. We propose that this anti-idiotypic response is mediated by "Type 2 autoreactive" T cells that are induced in peripheral lymphoid tissues following interaction with the particular idiotype expressed by the anti-self-I-A T cells. Thus, we define this phenomenon as an idiotype-restricted MHC-related cell interaction. To study the ontogeny of this response, we examined the distribution of Type 2 autoreactive cells. Spleen and lymph node but not thymic C57BL/6 T cells vigorously proliferate to T1.203. Mature (PNA-) as well as immature (PNA+) thymic T cells respond poorly. The frequency of cells responding to T1.203 is far greater in the spleen than in the thymus. The responding T cells were of both Lyt 1+ and Lyt 2+ T phenotype. The results suggest that Type 2 autoreactive cells are induced in peripheral lymphoid tissues following interaction with anti-I-A autoreactive T cells which escape from the thymus or develop in the periphery.

Enhancement of human T lymphocyte functions by prothymosin alpha. I. Augmentation of mixed lymphocyte culture reactions and soluble protein-induced proliferative responses

Prothymosin alpha (ProT alpha), a 115-amino-acid thymic polypeptide, was tested for its effect on soluble antigen, allo- and auto-antigen-induced human T-cell proliferation. ProT alpha enhanced the secondary T-cell proliferative response to ovalbumin (OVA)- and keyhole limpet haemocyanin (KLH)-pulsed antigen-presenting cells (peripheral blood monocytes). Maximum enhancement (20-fold for OVA and 23-fold for KLH) occurred when suboptimal concentrations of either OVA or KLH were employed. Subset depletion experiments showed that the helper/inducer T-cell subpopulation was responsible for the observed enhancement. In the mixed lymphocyte reaction (MLR), ProT alpha enhanced autoantigen- (autoMLR; 9- to 14-fold) as well as the alloantigen- (alloMLR; 8- to 10-fold) induced T-cell proliferation when suboptimal ratios of the participating cells were used. Preincubation of the stimulating (autologous or allogeneic monocytes) with ProT alpha induced significantly higher T-cell proliferation in both primary and secondary MLR responses as compared to that induced by non-treated monocytes. In contrast, T lymphocytes pre-incubated with ProT alpha did not show enhanced proliferative activity when tested subsequently in the MLR. Suboptimal numbers of T cells exhibited high proliferative activity when pre-incubated with ProT alpha in the presence of autologous monocytes. These studies suggest that ProT alpha potentiates T-cell proliferative responses not directly, but via monocytes which are included in the cultures either as antigen-presenting cells or accessory and/or stimulator cells. The importance of ProT alpha in pathologically occurring defective cellular immune response systems discussed.

Xenogeneic recognition of soluble and cell surface HLA class II antigens by proliferative murine T cells

In order to characterize the murine anti-human xenogeneic mixed lymphocyte reactions (MLR), we studied T cell proliferative responses against various human lymphoid cells by immunization of mice either with cellular or purified HLA-DR antigens. Data presented here indicated that small amounts of soluble HLA-DR antigen were able to prime mice, and that the xenogeneic MLR depends on the expression of HLA class II antigens on the stimulating cells. Experiments using a mutant cell line clearly showed that HLA-DP molecules were also sufficient in eliciting a primary or a secondary xenogeneic MLR while no secondary proliferative response was obtained with cells expressing only HLA class I molecules. Using a large panel of human cells with various haplotypes, our results also showed that (a) nonpolymorphic determinants of HLA class II antigens trigger dominantly the murine T cells and (b) the xenogeneic response required I-E and L3T4 accessory molecules and was not inhibited with anti I-A and monomorphic anti-HLA class II antigen monoclonal antibodies. Altogether these results suggest that HLA class II antigens act as nominal antigens in triggering a murine anti-human proliferative response.

Immunoregulatory effects of fraction 5 thymus peptides. I. Thymosin alpha 1 enhances while thymosin beta 4 suppresses the human autologous and allogeneic mixed lymphocyte reaction

Thymosin alpha 1 and thymosin beta 4, two peptides isolated from preparations of calf thymus fraction 5, were tested in the human mixed lymphocyte reaction (MLR). Thymosin alpha 1 was found capable of enhancing both the allogeneic and autologous MLR. On the contrary, thymosin beta 4 suppressed MLR proliferative responses. Study of the responses of the T cell subpopulations revealed that T4+ (helper/inducer) cells but not T8+ (suppressor/cytotoxic) are responsible for the enhanced, proliferative response to allo- and autoantigens in the presence of thymosin alpha 1. Both the autologous and the allogeneic proliferative responses of either T4+ cells or T8+ cells were not influenced by the addition of thymosin beta 4 in the cultures. However, when T4+ and T8+ subsets were cocultured, thymosin beta 4 was capable of activating T8+ cells to suppress the allogeneic and the autologous proliferative response of T4+ cells. These studies show that thymosin fraction 5 peptides exert immunoregulatory effects on the human MLR proliferative responses in vitro.