Immunological effect of two synthetic peptides containing alanine or D-alanine instead of acetyl group of thymosin beta 4 after treatment of human serum.

Two analogs of thymosin beta 4 the N-terminal acetyl groups of which were substituted by Ala or D-Ala, were synthesized by the solution method and studied for their immunological effect on the impaired blastogenic response of T-lymphocytes isolated from uremic patients after treatment of human serum. One of the synthetic analogs, D-Ala-thymosin beta 4 demonstrated a restorative effect on these patients when incubated in human serum, but the other analog, Ala-thymosin beta 4, showed no restorative effect under the same conditions. These results seem to suggest that D-Ala-thymosin beta 4 increases resistance to proteolytic degradation by exopeptidases more than Ala-thymosin beta 4.