Enhancement of the immunocompetence in neonatal guinea pigs by a thymic factor (TS).

The immunocompetence of newborn guinea pigs was evaluated in comparison with that of adults. The capacity of spleen cells from neonatal guinea pigs to produce antibodies to SRBC was found to be reduced, while no differences were observed in the capacity of those cells to respond to mitogenic stimulation or to form E rosettes with rabbit red blood cells. The in vivo treatment of newborn animals with a thymic factor (TS) induced an increase in the number of antibody-producing cells and an increase in the response to mitogenic stimulation but no variation in the number of rosette-forming cells. The effect of TS on both responses to SRBC and to mitogenic stimulation, was dose dependent.