Retention of acquired resistance to C. albicans by mice during short term immunosuppression

Forty inbred BALB/c mice (experimental mice) were exposed to C. albicans (5 x 10(6)cfu/ml) for a period of three days via their drinking water on two consecutive occasions. This was followed by an intraperitoneal injection of cyclophosphamide (250 mg/kg). Thirty control mice which had not been in contact with C. albicans received a similar dosage of cyclophosphamide. Three days later both groups were inoculated with C. albicans as described above. Groups of mice were randomly selected 2 and 18 days after the Candida exposure, cultures taken from their mouths and faeces, killed and their oral cavities examined for candidal lesions. In addition the faeces of mice were also examined ten days after the exposure to Candida. The experimental mice developed significantly smaller and fewer oral lesions and yielded less candidal growth than control mice. This pattern indicates that mice, which had been infected with C. albicans prior to immunosuppression, could retain some resistance to C. albicans during the suppressed phase. It is proposed that such a resistance is an acquired humoral immune response, most likely due to secretory IgA antibodies, which will protect the mucous membranes from severe infestation by Candida. In addition the histology of the candidal lesions indicates that histiocytes in the lamina propria, albeit scanty, may play an active role in the limitation of candidal infestation of the mouth.