Thyroid epithelial cell-specific CD4+ and CD8+ T cell lines were isolated from thyroid infiltrates of mice undergoing experimental-induced autoimmune thyroiditis. Thyroid-specific cell lines and clones proliferated and generated IL-2 in response to thyroid antigens and exhibited cytotoxic T lymphocyte (CTL) activity that is thyroid-specific and H-2 class I self restricted. These cells are TCR alpha-beta+ and exhibit a broad spectrum of Vbeta usage. Patients with systemic lupus erythematosus (SLE) exhibited both T helper cell (Th) and antigen presenting cell (APC) defects. The Th defects were complex in that different patients were identified whose peripheral blood leukocytes (PBL) were: 1) functionally intact; 2) unresponsive to recall antigens but responsive to HLA alloantigens but responsive to HLA alloantigens (ALLO) and phytohemagglutinin (PHA); 3) unresponsive to recall antigens and ALLO, but responsive to PHA; and d) unresponsive to all of these stimulus. Approximately 80% of SLE patients also exhibit a defect in APC function. The Th defects were associated with a decrease in IL-2 production, but an increase in IL-4 production, and in some patients, an increase in IL-10 production.