Responsiveness of human T-lymphocyte subpopulations in autologous mixed-lymphocyte reaction using xenoprotein-free separated cells: autologous reactivity lies chiefly in a low density T-cell fraction

Interferon gamma modulates the ability of autologous non-T cells to stimulate T cells to produce and respond to interleukin 2

The interactions of T-cell receptor with self-Ia antigen on non-T cells induced IL-2 production and IL-2 receptors on the cell surface and thus responsiveness to IL-2 of T cells in autologous mixed-lymphocyte reaction (AMLR). Four-day-cultured autologous non-T cells lost their ability to stimulate T cells to produce and respond to IL-2 with concurrent decrease of HLA-DR and HLA-DQ antigen expressed on the cell surface. Culturing of non-T cells with 500 U/ml of recombinant interferon gamma (IFN-gamma) maintained their stimulating ability which was otherwise lost. Treatment of non-T cells with monoclonal anti-HLA-DR or anti-HLA-DQ antibody before mixture with T cells abrogated their ability to induce IL-2 production and IL-2 responsiveness of T cells. The combined data suggested that Ia antigen expressed on non-T cells is modulated by IFN-gamma, which increases the ability of non-T cells to stimulate autologous T cells to produce and respond to IL-2.

Improvement of decreased interleukin 2 (IL-2) responsiveness and IL-2 production in autologous mixed-lymphocyte reaction of cord blood lymphocytes by interferon-gamma and IL-2 and the role of HLA-DQ antigen

Cord blood T cells did not produce interleukin 2 (IL-2) nor acquire responsiveness to it in autologous mixed-lymphocyte reaction (AMLR) as they do when activated by phytohemagglutinin (PHA). The ability of the cells to respond to IL-2 was restored either by the addition of recombinant IL-2 to the AMLR culture or by the preculture of non-T stimulator cells with recombinant interferon-gamma (IFN-gamma). IL-2 production was also induced when the T cells were added with recombinant IL-2 at the initiation of the AMLR culture, preceded by the treatment of non-T cells with recombinant IFN-gamma. IL-2-producing cells of cord blood induced in the above-mentioned condition were defined to be OKT4+ T cells, because the deletion of OKT4+ T cells from T-cell population abrogated the reaction, while that of OKT8+ T cells did not. Acquisition of IL-2 responsiveness and IL-2 production of T cells seemed to be mediated by HLA-DR and HLA-DQ molecules of non-T cells because these reactions were blocked by the treatment of non-T cells either with monoclonal anti-HLA-DR or with anti-HLA-DQ antibody. The HLA-DR and HLA-DQ densities of cord blood non-T cells were low as compared with those of adult, but the expression of HLA-DQ was remarkably improved by IFN-gamma treatment. In regard to IL-2, both IFN-gamma and IL-2 were needed to enable the lymphocytes to produce. This may suggest that some functional maturation by IL-2 of responder T cells is further required. These combined data suggested that cord blood non-T cells are defective as a stimulator in AMLR and this could be corrected by enhancing the expression of HLA-DQ antigen.

The role of xenoantigen in the human autologous mixed lymphocyte reaction: ability to respond in the absence of exposure to xenoantigen depends on the method of T-cell preparation

Recent reports have suggested that the autologous mixed lymphocyte reaction (AMLR) is attributable to contaminating xenoantigen. T-cell populations separated from peripheral blood mononuclear cells (PBM) over Percoll fail to produce an AMLR in the absence of xenoantigen. However, T-cell populations that do not adhere to plastic and to nylon wool will in the absence of added xenoantigen produce an AMLR comparable to that obtained with E-rosetted populations. In the nonadherent cells separated sequentially by passage through nylon wool and Percoll, the presence of two lymphocyte subpopulations was demonstrated. One is xenoantigen dependent, the other xenoantigen independent in the AMLR. Further, the xenoantigen-independent population may provide help to the dependent population. In the previous reports with Percoll-separated cells that attributed the AMLR to contaminating xenoantigen, the xenoantigen-independent T-cell population was excluded from the responding fraction.