Thymosin treatment: serum corticosterone and lymphocyte mitogenesis in moderately and severely protein-malnourished mice.

The present studies were performed to determine the levels of serum corticosterone (SC) and the proliferation of lymphocytes in response to phytohemagglutinin (PHA) in mice that were injected with thymosin fraction V and fed low protein diets. We found that protein-malnourished mice had consistently higher SC values than the control animals. This result confirms the existence of nutritional stress, which stimulates the adrenal glands increasing the release of corticosteroid hormones. No changes were observed in the SC level in controls whether or not thymosin was injected. However, in mice fed a protein-deficient diet, there was a significant decrease in SC levels after thymosin treatment, as compared to those of groups not treated with thymosin. Additionally, the thymosin effect on the SC levels was correlated with the cell-mediated immune changes. A significant increase in both PHA and lipopolysaccharide-induced lymphocyte transformation was observed in spleen cells from malnourished mice treated with thymosin fraction V. Thus, stress-induced glucocorticoid immunosuppression was demonstrated in malnourished mice. Our results suggest that components of thymosin fraction V may be involved in the mechanism of the restoration of lymphocyte transformation that was suppressed by glucocorticoid in protein-malnourished mice.