Possible Role of Trichophytin Antigen in Inducing Impaired Immunological Clearance of Fungus in Onychomycosis.

The immunology of onychomycosis is poorly understood. Th1 and Th17 are the principal effector cells responsible for protective immunity against fungi, while it is assumed that Th2 responses are associated with deleterious effects. The study was conducted to appraise the role of interleukin-6 (IL-6), transforming growth factor β (TGF-β) and immunoglobulin E (IgE) in onychomycosis patients and to study skin reactivity to trichophytin antigen in them. Serum samples of 60 cases of chronic onychomycosis and 30 healthy controls were assayed for serum IgE, IL-6 and TGF-β levels using specific immunoassay kits; 0.01 ml of trichophytin antigen, Candida antigen and phosphate-buffered saline using separate syringes were injected intradermal at three independent sites of the forearm in cases and controls. Serum IL-6 levels were significantly lower in cases as compared to controls, while serum TGF-β levels in both cases and controls were comparable. Serum IgE levels in cases were significantly higher when compared with controls. Thirty-eight patients showed immediate hypersensitivity response to trichophytin antigen, while none showed delayed hypersensitivity reaction to trichophytin antigen. Constant fungal antigenic stimuli induce a state of anergy as indicated by low serum IL-6 levels and the absence of delayed hypersensitivity reaction to trichophytin antigen in cases, leading to chronicity of infection. High total IgE may indicate a high probability of prior fungal sensitization.