Regulation of thymocyte proliferation by alpha beta TcR+ CD3+ CD4- CD8- cloned natural suppressor (NS) cells

Prednisolone inhibits LPS-induced bone marrow suppressor cell activity in vitro but not in vivo

Glucocorticoids are used clinically to treat a variety of inflammatory diseases including endotoxemia. We hypothesized that injecting mice with the steroid prednisolone (pred) would mitigate the enhanced bone marrow (BM) natural suppressor (NS) cell activity that occurs in mice after receiving an injection of lipopolysaccharide (LPS). In vitro, prednisolone blocked the ability of NS cells to produce the immunosuppressive molecule nitric oxide (NO) and also the ability to suppress T cell proliferation. Prednisolone acted both indirectly, by blocking synthesis of cytokines necessary for NS cell activation, and also directly on NS cells, by blocking production of NO. In vivo, variable results were obtained. Prednisolone at 20 microg/gm did decrease NS activity when injected into normal mice. However, when mice were injected with both LPS and prednisolone (0.2 or 20 microg/gm), a large increase in BM NS activity was observed. The increase was evident in both the ability of the BM cells to suppress T cell proliferation and to produce NO. The data show that, in vivo, the steroid prednisolone in conjunction with the inflammatory compound LPS act to enhance BM NS activity.

Early appearance of T cell receptor alpha beta + CD4- CD8- T cells with a skewed variable region repertoire after infection with Listeria monocytogenes

We found that the number of T cell receptor (TCR) alpha beta + CD4- CD8- T cells increased in the peritoneal cavity on day 5 after an intraperitoneal infection with Listeria monocytogenes strain EGD together with TCR gamma delta + CD4- CD8- T cells. Thereafter, the TCR alpha beta + CD4- CD8- T cells decreased to a normal level by day 14. The TCR alpha beta + CD4- CD8- T cells showed an activated T cell phenotype (L-selectin CD44 +) and expressed CD45/B220 and interleukin-2 receptor beta, but did not express heat stable antigen, which is expressed by the immature CD4- CD8- thymocytes. Furthermore, 20-30% of the TCR alpha beta + CD4- CD8- T cells expressed the NK1.1 natural killer cell marker. Analysis of the TCR V region repertoire of the TCR alpha beta + CD4- CD8- T cells induced by L. monocytogenes infection showed that more than 80% of the TCR alpha beta + CD4- CD8- T cells expressed TCR V beta 8 detected by anti-TCR V beta 8.1 and 8.2 mAb, and a reverse transcription-polymerase chain reaction analysis of V alpha 14 relative to V alpha 11 expression revealed that the TCR alpha beta + CD4- CD8- T cells expressed a higher level of V alpha 14, which was reported to be preferentially expressed by TCR alpha beta + CD4- CD8- thymocytes rather than conventional CD4+ T cells. The TCR alpha beta + CD4- CD8-T cells showed a proliferative response to anti-TCR alpha beta mAb stimulation. In contrast, they showed no response to stimulation with either Listeria antigen or 65-kDa heat shock protein of Mycobacterium bovis, which do stimulate the Listeria-specific TCR alpha beta + CD4- CD8- T cells and the Listeria-induced TCR gamma delta + T cells, respectively. These results suggest that the TCR alpha beta + CD4- CD8- T cells may recognize a restricted set of self antigens induced by L. monocytogenes infection, and that they contribute to host protection at an early stage of infection.

Identification of a factor(s) from cloned murine natural suppressor cells that inhibits IL-2 secretion during antigen-driven T cell activation

Crude supernatants were obtained from cloned murine natural suppressor (NS) cells activated in vitro with phorbol-myristate-acetate (PMA) and calcium ionophore (A23187). Supernatants suppressed IL-2 production in the mixed leukocyte reaction (MLR) with BALB/c spleen cells, but no reduction was observed in the response to PHA, Con A, or anti-CD3 antibody. Suppressive activity was partially purified by DEAE ion exchange chromatography, and inhibited the antigen-presenting function of the macrophage line 1G18-LA in an assay system with the ovalbumin-specific T cell hybridoma, 3DO-18.3. In addition, the antigen-presenting function of the A20 B cell line was inhibited in an assay with a sperm whale myoglobin (SpWMb)-specific T cell hybridoma (8.2.1d.H1a). Results with blocking antibodies suggest that this factor appears to be a unique cytokine.