Partial purification and characterization of systemic lupus erythematosus derived factors that suppress production of interleukin-2.

We report here on interleukin-2 (IL-2) suppressive factors, synovial fluid (SF) peripheral blood mononuclear cells (PBM), derived from short term cultures of unstimulated PBM of patients with systemic lupus erythematosus (SLE). SF PBM suppressed production of IL-2, but not proliferative responses to this lymphokine. It was sensitive to acid (pH 2.6), heat (56 degrees C), and tryptic digestion. It retained activity in the presence of 2-mercaptoethanol (2-ME), had no interferon activity and no non-specific cytotoxicity. Although crude SF PBM contained IgG and PGE2, these were not associated with its 2 active fractions. SF PBM was partially purified on a G-200 Sephadex column. IL-2 suppressive activity was detected in 2 fractions of molecular weights corresponding to greater than 150 kD and 40-60 kD, the latter acting only in the presence of monocytes. SF PBM appear to affect directly the IL-2 producer cell, since it suppressed IL-2 production by (1) mitogen stimulated PBM depleted of CD8+ suppressor cells and by (2) mitogen induced Jurkat cells. These "spontaneous" suppressive factors were ubiquitous in SLE, and may be important tools for studying the defective IL-2 production in SLE and its significance in the development of the disease.