Studies reported during the past year have added new knowledge to our understanding of the pathogenesis of systemic lupus erythematosus. A study of sibpairs with lupus revealed a strong linkage of a region located at chromosome 1q41-42 that crossed ethnic barriers. B-cell receptor-initiated signaling events, such as tyrosine protein phosphorylation and intracellular calcium concentrations, were found to be increased in patients with lupus in a disease- and clinical activity-independent manner. T cells from patients with lupus express increased amounts of the CD40 ligand, which is functional because it helps B cells to produce anti-DNA antibodies and express more CD80 (B7-1) on their surface. Only occasionally do lupus patients display structural defects of either Fas antigen or ligand molecules, and although spontaneous apoptosis is increased in lupus cells (as well as in other systemic autoimmune disorders), the activation-induced T-cell death is defective.