Targeted disruption of the transforming growth factor-beta 1 (TGF-beta 1) gene in mice results in the development of a massive multifocal inflammatory disease in many tissues. Because no detectable pathogen was identified, we examined whether autoimmune mechanisms played a role in initiating or maintaining the inflammatory disease. The serum of TGF- beta 1 knockout mice contained elevated titers of antibodies to nuclear antigens (ssDNA, dsDNA, Sm, and RNP) as well as reactivity against the 16/6 idiotype (16/6 Id). In addition, Ig deposits were detected in renal glomeruli of TGF- beta 1 knockout mice. Transplantation of TGF- beta 1 knockout hematopoietic cells into normal irradiated recipients resulted in a similar profile of autoantibody production as well as in the induction of inflammatory lesions. Our results describe autoimmune activity that ensues when the TGF-beta 1 cytokine is absent.

Summary I nihis paper, the relative efficacy of macrophages, B cells and splenic dendritic cells (SDC) in presenting West Nile virus (WNV) antigens to WNV memory CD4"'' T cells is examined. The results indicate that, under appropriate conditions, all these ceil types can function as antigen-presenting cells (APC). Li.sicria-mduccii peritoneal macrophages induced higher proliferativc responses than SDC or B cells derived from naive or 14 day WNV-primcd mice. The ability of Z.mma-induced macrophage populations to present antigen was specifically inhibited by anti-Class II major histocompatibility complex (MHC) antibodies. On a cell population basis. B cells obtained from mice primed with WNV 14 days previously evoked higher responses than resting B cells. B eells from mice receiving weekly injections ofWNV over a period of4 weeks elicited optimal responses with lowerdoses of antigen than naive or 14 day WNV-primed B cells. When macrophages were used as APC. addition of specific antibodies to WNV resulted in increased eHicieney of presentation, probably due to increased uptake of antigen by opsonization. In contrast, addition of anti-WNV antibodies to hyperimmune B cells reduced their clficacy presumably by rcdueing uptake of antigen by B eell surface immunoglobulin. When SDC from C57BL/6 mice were used as APC. WN'V-specificproliferative responses were directly related to the number of stimulator cells used, and the background proliferation with moek antigen was two-to five-fold lower than specific responses. Higher levels of background proliferation were stimulated by SDC from CBA/H mice so that the antigen-specific responses were always less than two-fold higher than background.

West Nile virus (WNV)-specific murine T-cell proliferation in vitro was investigated in terms of conditions that optimize antigen-specific responses and reduce background proliferation. The responder populations consisted of splenocytes from WNV-primed mice enriched for L3T4+ T cells. Ia+ antigen-presenting cells (APC) were derived from splenocytes of WNV-primed or naive mice. Antigen was a lysate prepared from WNV-infected Vero cells at 12 h postinfection. Strong virus-specific proliferative responses were observed when antigen-pulsed APC were cocultured with responders at a 1:1 ratio. Substantial nonspecific proliferation occurred when culture medium supplemented with 5% fetal bovine serum (FBS) was used, whereas with 1% normal mouse serum a higher degree of antigen specificity was evident, although the magnitude of the responses was lower. The best separation between antigen-specific and background proliferation was obtained by using an exogenous source of T-cell growth factors to amplify for 2 days the proliferation of L3T4+ cells triggered by an initial 3 days of culture with antigen-pulsed APC. This investigation has defined optimal conditions for investigating the stimulation of WNV-primed L3T4+ T-cell proliferation in response to the presentation of viral gene products by Ia+ APC. This assay should permit detailed analysis of the efficiency of various APC populations and identification of viral antigens that stimulate the proliferation of Class II MHC-restricted T cells.