Resistance and susceptibility to infection in inbred murine strains. III. Effect of thymosin on cellular immune responses of alloxan diabetic mice.

Three parameters of cell-mediated immunity, namely, (a) resistance to infection with Candida albicans, (b) in vivo release of migration inhibitory factor (MIF) into the circulation and (c) delayed hypersensitivity were markedly reduced when mice of such normally resistant high responder strains as C57B1/10SNJ and C57B1/KsJ became hyperglycaemic after treatment with alloxan. When the alloxan diabetic mice were inoculated daily intraperitoneally with thymosin fraction 5, beginning 3 days before infection, resistance to infection was greatly enhanced. When the mice were administered 5 micrograms thymosin fraction 5 for 3 days before sensitization and for 3 days before challenge, the amount of MIF released in vivo into the circulation after the antigenic challenge was much greater. When the mice were treated daily with 5 micrograms thymosin fraction 5, beginning on the day of sensitization, the capacity to develop delayed footpad reactions was increased. Thus, the treatment of alloxan diabetic mice with thymosin fraction 5 enhanced the three parameters of cell-mediated immunity that were under investigation.