INCREASED INTERLEUKIN-2 LEVELS DURING STANDARD TRH TEST IN MAN

Interleukin-2 (IL-2) is a pluripotential cytokine that, besides its role in the regulation of immunocompetent cells function, also stimulates hormone secretion. On the other hand, several factors, including cytokines (interleukin-1, IL-1; interleukin-6, IL-6) and pituitary hormones (thyrotropin, TSH; prolactin, PRL), exert stimulatory effects on T-cell connected IL-2 production. In order to evaluate the role of both pituitary hormones in the activation of the immune system, the following two standard diagnostic tests were performed: TRH test (0.2 mg) in 8 healthy human subjects (4F/4M) aged 18-50 years, and oral metoclopramide (MCP) test (10 mg) in 8 females with galactorrhea and regular menstruation aged 18-52 years. The mobilization (peak response) of PRL, TSH, triiodothyronine (T-3), thyroxin (T-4), IL-1 beta, IL-2, IL-6 in TRH test, and PRL, IL-1 beta, IL-2, IL-6 for MCP test were evaluated. The responses of TSH (2.0 +/- 0.3 vs 12.3 +/- 2.2 mu IU/ml, p < 0.01), PRL (15.3 +/- 2.3 vs 46.4 +/- 8.8 ng/ml, p < 0.01), T-3 (178.0 +/- 16.4 vs 248.7 +/- 21.1 ng/dl, p < 0.001), T-4 (7.9 +/- 0.4 vs 9.6 +/- 0.5 mu g/dl, p < 0.001), and IL-2 (45.6 +/- 7.8 vs 79.9 +/- 16.4 fmol/ml, p < 0.05) in TRH test were noted. The peak response of PRL (16.3 +/- 2.6 vs 107.7 +/- 22.4 ng/ml, p < 0.01) in MCP test was also observed, but without any changes in interleukin concentrations. The results suggest that TSH or TSH plus PRL exert a more pronounced immunostimulatory effect on IL-2 secretion than PRL itself, and that the standard TRH test appears to be a useful method of evaluation of the immune response in human subjects.