Resistance and susceptibility to infection in inbred murine strains. I. Variations in the response to thymic hormones in mice infected with Candida albicans

Nine inbred murine strains were either highly resistant or highly susceptible to intravenous challenge with 4 X 10(4) to 1 X 10(5) cells of Candida albicans. The resistant strains had the capacity to develop delayed footpad reactions on appropriate sensitization and challenge; the susceptible strains did not have this innate capacity. Administration of thymosin fraction 5 beginning on the day of infection greatly increased the resistance of the susceptible strains to infection, but decreased the resistance of the resistant strains. In contrast, thymosin fraction 5 enhanced the delayed footpad responses of resistant-sensitized mice to specific antigen, but did not have a detectable effect on the delayed footpad reactions of the susceptible strains. Reinfection of the two types of strains had different effects, in that, depending on the strain, resistance could be increased, decreased, or not influenced at all.