Examination of the effect of age and acquired immunity on the susceptibility of mice to infection with Aspergillus fumigatus.

Adult CBA mice showed considerably greater resistance to experimental infection with Aspergillus fumigatus than young animals of the same strain (P less than 0.01). Furthermore, in contrast with the young mice, the susceptibility of the adults was only moderately increased by treatment with cortico-steroids. On the other hand, immunosuppressive treatments producing severe depression of lymphocyte function greatly increased susceptibility to lethal infection and promoted fungal growth in a wide range of tissues. These observations suggested a role for specific acquired immunity in the relatively high resistance to experimental aspergillosis shown by older mice.