Thymulin modulates cytokine release by peripheral blood mononuclear cells: a comparison between healthy volunteers and patients with systemic lupus erythematosus.

Thymulin is a nonapeptide hormone isolated from the thymus gland. It has immunomodulatory effects which have not yet been well defined. Its major actions have been shown to be on T-cells and their immature precursors. In this study, thymulin was tested in vitro for its effect on the release of IL-1 alpha, IL-2, IL-6 and TNF alpha from peripheral blood mononuclear cells (PBMC) obtained from normal volunteers and patients with active systemic lupus erythematosus (SLE). In our experiments, PBMC (stimulated with LPS or PHA) were cultured for 24 h in the presence of 1,100 or 1,000 ng/ml of thymulin. Supernatants were subsequently assayed for cytokine activities using commercially available ELISA (IL-2, IL-6 and TNF alpha) and RIA (IL-1 alpha) kits. Thymulin (1 ng/ml) resulted in a significant (p < 0.01) increase in IL-1 alpha in the volunteers and a significant (p < 0.05) inhibition of this cytokine at all dose levels tested in SLE patients, whose basal levels of IL-1 alpha were significantly (p < 0.05) higher. Thymulin significantly (p < 0.05) inhibited IL-2 only in SLE patients at 1,000 ng/ml. At all dose levels tested, thymulin significantly (p < 0.01) inhibited IL-6 in volunteers, and, only at 1,000 ng/ml, it significantly (p < 0.05) inhibited it in patients with SLE. At the 1,000 ng/ml dose level, TNF alpha was significantly (p < 0.05) inhibited in both volunteers and SLE patients, whose basal levels of this cytokine were significantly (p < 0.05) higher.(ABSTRACT TRUNCATED AT 250 WORDS)