No abstract

No abstract

Treatment of lymphocytes with inducers of interferon a (IFN-a) results in the production of corticotropin (ACTH) and endorphin-like activities. The pro-opiomelanocortinderived hormones ACTH and a-, (-, and y-endorphin and the structurally related hormones [Leu]-and [Metlenkephalin were therefore tested for their effects on the in vitro antibody response ofmouse spleen cells. ACTH and a-endorphin were potent inhibitors (.80% suppression) of the antibody response to the T-celldependent antigen sheep erythrocytes at a concentration of 0.5 p.M.[Met]-and [Leu]enkephalin were moderate inhibitors (approximately 60% suppression) at 0.2-2 FM, and (-and y-endorphin were minimal inhibitors (approximately 20% suppression) at 5-6 pAM. At higher concentrations ACTH also inhibited the antibody response to the T-cell-independent antigen dinitrophenylFicoll, suggesting that T-cell function was more sensitive to blockage by these hormones than was B-cell function. ACTH and IFN had similar suppression properties; thus, the hormone-like activities associated with IFN-a may play a role in IFN-induced immunosuppression. a-Endorphin immunosuppression was blocked by naloxone, which suggested that a-endorphin exerted its effects through binding to opiate-like receptors on the spleen cells. The failure of (3-endorphin to suppress the immune response significandy was not due to its failure to bind to the opiate-like receptors because it blocked a-endorphin-induced suppression. Direct evidence for both opiate and ACTH receptors on the spleen cells was obtained in binding studies with labeled enkephalin and ACTH. Such studies revealed the presence of both high-and low-affminty receptors. The data show that neuroendocrine polypeptide hormones can regulate the immune response.It has been shown recently that interferons (IFNs) have hormonal or hormone-like activities and share common pathways of cell activation with polypeptide hormones (1-3). Additionally, based on biological, biochemical, and antigenic characterization, we have shown that human lymphocytes stimulated with IFN-a inducers produce corticotropin (ACTH) and endorphin-like substances (4-6). The findings support a regulatory circuit between the immune and neuroendocrine systems which operates by known hormones that are common to both systems. RESULTS AND DISCUSSIONACTH suppressed the C57BL/6 mouse spleen cell PFC response to both SRBC (T-cell-dependent antigen) and DNP-Ficoll (T-cell-independent antigen) as shown in the dose-response curves (Fig. 1). The slopes for ACTH suppression of the antibody response to the two antigens were essentially the same, but the anti-SRBC response was more sensitive to suppression. Approximately 80% of the anti-SRBC PFC response was suppressed with 0.5 AM ACTH, whereas 2 A.M was required for comparable suppression of the anti-DNP-Ficoll response. Treatment of spleen cells with anti-Thy 1.2 antibody in order to remove T cells did not alter ACTH suppression of the anti-DNP-Ficoll PFC response (data not shown). Thus, ACTH suppressed the antibo...

Glioblastoma is a highly aggressive form of brain cancer characterized by uncontrolled cell growth resulting from a loss of cell cycle regulation. In this study we determined the antiproliferative eects of interferon gamma (IFNg) on the glioblastoma cell lines T98G, SNB-19 and U-373, focusing on the ability of IFNg to increase levels of p21, an important negative regulator of cell cycle events. IFNg was found to inhibit the growth of all cell lines, with inhibition ranging from 82.2% to 45.4%. Flow cytometry analysis showed that IFNg treatment caused a cell cycle delay in the G 1 or S phases. The strength of this delay varied, correlating with the degree by which IFNg inhibited proliferation of each cell line. IFNg treatment increased the production of the cyclin dependent kinase inhibitor (CKI) p21 /cyclin-dependent kinase 2 (cdk2)/cyclin showed that the amount of p21 WAF1/CIP1 in the complexes and the inhibition of cdk2-cyclin kinase activity correlated with the level of p21 WAF1/CIP1 produced in the cells by IFNg. These results show that IFNg has signi®cant antiproliferative eects on the glioblastoma cell lines and suggest that p21 WAF1/CIP1 plays a role in mediating these eects.

We have previously identified a nuclear localization sequence (NLS) in interferon-gamma (IFN-gamma). This NLS functions intracellularly by forming a complex with its transcription factor Stat1alpha and the nuclear importer of Stat1alpha, the importin-alpha analog NPI-1. The stability of this complex and the subsequent nuclear translocation of the complexed Stat1alpha are dependent on the integrity of this NLS, showing that Stat1alpha nuclear import is mediated by the IFN-gamma NLS. In this study, to directly evaluate the intrinsic requirement of nuclear IFN-gamma toward its biologic activities, we engineered a chimeric in which the IFN-gamma NLS has been substituted by a heterologous NLS, namely, the prototypical NLS of the SV40 large T antigen, which would drive nuclear translocation of IFN-gamma in a sequence-nonspecific manner. The chimeric, IFN-gamma-SV, was equally active in antiviral and antiproliferative assays as the wild-type IFN-gamma. Interestingly, IFN-gamma-SV was also translocated to the nucleus and was also recovered intracellularly as a complex with the Stat1alpha importer NPI-1, like wild-type IFN-gamma. Comparison with an NLS deletion mutant showed that deletion or changes within the NLS motif of IFN-gamma were inconsequential to the high-affinity extracellular binding to the IFN-gamma receptor complex, yet the presence of an NLS was critical to the expression of the biologic activities of IFN-gamma and its NPI-1 complexation ability. Our data conclusively demonstrate that nuclear translocation of IFN-gamma is an intrinsic requirement for the full expression of the biologic activities of IFN-gamma and strengthen the conclusion that nuclear chaperoning of Stat1alpha is the primary role of IFN-gamma nuclear translocation. This type of ligand imprinting by sequestering of activated Stat may contribute to the specificity of Stat nuclear transcription.