Impaired T-cell activation in patients with systemic lupus erythematosus

Interleukin-2 (IL-2) production was studied in T lymphocytes from 32 patients with systemic lupus erythematosus (SLE) and 27 healthy volunteers. The IL-2 production by phytohemagglutinin (PHA)-stimulated cells from SLE patients was significantly depressed compared to control values, with a correlation between degree of depression and disease activity. The depressed IL-2 production by SLE T cells are largely reversed by the addition of either phorbol ester (PMA) or partially by a calcium ionophore. SLE T cells had significantly lower peak increases in intracellular free calcium ([Ca²⁺]_i) than controls after stimulation by PHA or by a monoclonal antibody against the CD3 antigen. This abnormality was found even in T cells from patients with mild disease activity or in those whose T cells produced normal amounts of IL-2. Calcium ionophore produced similar increases in [Ca²⁺]_i in SLE patients as in normals. These results suggest that a major component of the defect responsible for decreased IL-2 production by SLE lymphocytes is proximal to protein kinase C activation and may involve impaired signal transduction after activation of the antigen receptor complex.