Two areas of investigation are in progress. We have defined by isoelectric focusing a large array of IgG antibodies to ds DNA in the sera of murine models of SLE (NZB/NZW F1, MRL/l and BXSB strains). In contrast, renal eluates from these mice contain a restricted subpopulation of anti-DNA antibodies focusing at an alkaline pI. Similar monoclonal antibodies have been produced in murine hybridoma systems. We are attempting to produce anti-idiotypic antibodies to these monoclonal DNA antibodies; the anti-idiotypes will be used to suppress subpopulations in newborn syngeneic mice to determine pathogenicity of different subpopulations. In addition, serum factors from SLE patients which suppress the ability of normal circulating human monocytes to stimulate autologous T-cells in autologous MRL are being studied.