Defective expression of p70/75 interleukin 2 receptor in T cells from patients with systemic lupus erythematosus: a possible defect in the process of increased intracellular calcium leading to p70/75 expression.

Phytohemagglutinin (PHA) stimulated T cells from patients with systemic lupus erythematosus (SLE) showed hyporesponsiveness to interleukin 2 (IL-2) and expressed less p70/75 IL-2R than healthy controls. Ionomycine (IM, calcium ionophore) which selectively upregulated p70/75 expression, induced less p70/75 in patients with SLE than in healthy controls. However, intracellular calcium levels of T cells from patients with SLE increased as much as those from healthy controls, when T cells were stimulated by IM or PHA. Our results suggest that an impaired expression of p70/75 IL-2R in T cells from patients with SLE is not due to a defective calcium influx but to the events after the rise of calcium levels.