Effects of thymosin and insulin on suppressor T cell in type 1 diabetes.

In most studies the activity of suppressor T cells and the percentage of suppressor/cytotoxic T-lymphocyte subsets in type 1 diabetes have been found to be altered. To determine whether thymosin and insulin in vitro have a role in improving or normalizing these abnormalities, PBMC from 28 patients with type 1 diabetes of various durations were treated with thymosin or insulin and the activity and the percentage of suppressor T cells were detected by using the method of ConA-induced suppressor T cells and WuT8 (suppressor/cytotoxic) monoclonal antibody respectively. Both thymosin and insulin were found to have ability to improve and normalize the ConA-induced suppressor cell activity and the percentage of WuT8 cells in diabetic patients. Data have shown that the lower the activity and the percentage of suppressor T cells, the more intense the effects of both compounds. The strongest effects were found at the concentrations of 10 micrograms/ml thymosin and 10 ng/ml insulin. Thymosin was more effective than insulin. This experiment also suggested that the activated lymphocytes stimulated by mitogens (PHA or ConA) were required when insulin exerted a significant effect on suppressor T cells. We conclude that thymosin and insulin in vitro can exert immuno-regulatory or immunostimulating effects on suppressor T cells.