Model Dermatophytosis in Naturally Infected Subjects

Model infections with Trichophyton mentagrophytes var granulare were used to assay defenses to dermatophyte infection and to correlate defenses with immune mechanisms. Volunteers were immunologically classified as either experienced immune (El), if they manifested acquired resistance to clinical reinfection; or as chronically infected (CI), if they had evidence of long-standing tinea pedis, tinea corporis, or tinea cruris. The model partially confirmed the immunobiologic classification: the 9 El subjects were resistant to infection, while the 11 CI subjects who manifested type 1 humoral immunity (HI) with or without cell-mediated immunity (CMI), were susceptible to infection. A dichotomy in susceptibility to natural and model infections was noted in three CI subjects manifesting only CMI. It appears that deficient or compromised CMI is a correlate of susceptibility to both natural and model infections, whereas CMI alone correlates with resistance to glabrous skin infections. Individuals with apparently normal CMI may have inflammatory tinea pedis, which may relate to nonimmunologic factors peculiar to the feet.