cAMP differentially regulates expression of mRNA encoding IL-1 alpha and IL-1 beta in murine peritoneal macrophages.

The influence of PGE2 and the consequent rise in intracellular cAMP on LPS-induced IL-1 alpha and IL-1 beta mRNA levels has been examined in murine peritoneal macrophages. As has been previously reported, neither PGE2 nor dibutyryl cAMP modulated the levels of LPS-induced IL-1 alpha mRNA. In contrast, the levels of IL-1 beta mRNA were markedly potentiated (greater than 10 fold) under the same experimental conditions. This effect was due to elevation of intracellular cAMP because other agents known to elevate cAMP levels (e.g., cholera toxin, forskolin, 1-isomethyl-3-isobutylxanthine) had the same selective effect on IL-1 beta mRNA levels. PGE2 and dBcAMP not only potentiated LPS-induced IL-1 beta mRNA levels but were also able to stimulate modest accumulation of IL-1 beta mRNA in the absence of LPS. Although measurement of IL-1 activity by bioassay suggested that dBcAMP and PGE2 could suppress LPS-induced IL-1 expression, levels of IL-1 protein, determined by radioreceptor assay, were markedly elevated. cAMP did not appreciably alter the stability of either IL-1 alpha or IL-1 beta mRNA. Instead dBcAMP independently stimulated the transcriptional activity of the IL-1 beta gene. In concert the results demonstrate that cAMP can modulate the response of mononuclear phagocytes to LPS in a complex pattern; gene expression may be unaltered, suppressed, or potentiated and will thereby affect both the quality and magnitude of the ensuing inflammatory response.

OKT4+ cytotoxic T cells can lyse targets via class I molecules and can be blocked by monoclonal antibody against T4 molecules.

Human cytotoxic T lymphocytes (CTL) have been shown to recognize either class I or class II major histocompatibility (MHC) products. This recognition has been correlated with the expression of OKT antigens on the surface of the CTL. Thus, OKT4+ CTL have been shown to be reactive with class II products, whereas OKT8+ effectors recognize class I molecules. In this study, responder cells were separated according to their OKT4 or OKT8 cell surface phenotype on a fluorescence-activated cell sorter (FACS). The OKT4+ subsets were stimulated with an LCL mutant that did not express DR and MB/MT but did express SB and class I antigens. After 7 days in culture, the activated subsets were tested on a panel of class I matched or mismatched targets. The cytotoxicity observed could be correlated with the presence of matched class I antigens. In addition, monoclonal antibody (MCA) W6/32, directed at a monomorphic determinant on HLA-A and -B molecules, blocked lysis. Furthermore, six OKT4+ CTL clones were derived from the OKT4+ bulk cultures; three clones were found to be directed at class I molecules whereas the other three recognized class II determinants. The ability of these clones to lyse their relevant targets was blocked by OKT4 MCA, raising questions as to the role of the T4 molecule in antigen class-specific CTL recognition.

Genetic regulation of delayed-type hypersensitivity responses to poly (Tyr,Glu)-poly(DLAla)--poly(Lys): expression of the genetic defect in the induction and manifestation phases in H-2s and H-2f mice.

The genetic defect of H-2s and H-2s non-responder mouse strains in both the induction and manifestation phases of delayed-type hypersensitivity (DTH) responses to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L] was analysed. Utilizing an in vitro system to activate DTH effector T cells, we observed that non-adherent T cells of (H-2f X H-2b) F1 or (H-2s X H-2b)F1 responder mice, could not be activated on antigen bearing adherent cells of H-2f or H-2s haplotypes. On the other hand, these T cells were effectively sensitized on adherent cells derived from either F1 or parental (H-2b) responder mice. These results indicate that in these mouse strains the genetic defect, in the induction phase of DTH, is expressed at the level of the antigen presenting cell. In subsequent experiments, we were able to "correct' the non-responsiveness of H-2s recipients by transfer of educated and irradiated (H-2s X H-2b)F1 T cells together with normal F1 adherent cells. Normal non-adherent and nylon wool enriched T cells failed to restore these responses. Similarly, antigen-pulsed F1 irradiated peritoneal exudate cells could stimulate DTH responses in SJL recipients of (SJL X C57BL/6)F1 (T,G)-A--L educated cells. The genetic defect of H-2s mice in the manifestation phase of the DTH reaction is thus also expressed on the antigen presenting cell.