Effect of thymopoietin pentapeptide (TP5) on autoimmunity. I. TP5 suppression of induced erythrocyte autoantibodies in C3H mice.

C3H mice (young and old), when immunized with the cross-reacting rat erythrocytes, produced erythrocyte autoantibodies that usually persisted for more than 10 weeks. I.P. injection of thymopoietin pentapeptide (TP5) once or thrice weekly accelerated the loss of erythrocyte autoantibodies 7 weeks after immunization; 10 ng of TP5 was the optimal dose. The rat agglutinin responses of these immunized mice were unaffected by TP5 during the whole period of study. Spleen cells from rat erythrocyte-immunized mice, when transferred to syngeneic recipients undergoing similar immunization schedules, delayed the appearance of erythrocyte autoantibodies in the recipients. A greater delay was observed when spleen cells were taken from mice that had also received TP5 treatment.