TOPICAL APPLICATION OF T-2 TOXIN INHIBITS THE CONTACT HYPERSENSITIVITY RESPONSE IN BALB C MICE/

T-2 toxin, a trichothecene mycotoxin, has previously been shown to alt er immune functions and promote skin tumors. We demonstrate that topic ally applied T-2 toxin reduces the ear swelling response to oxazolone challenge in BALB/c mice. For this reduction in ear swelling to occur, toxin application must be at, or within, 1 h after challenge. Dose-re sponse studies showed a 44% reduction in ear swelling with 30 ng of T- 2 toxin as compared with a similar reduction with 300 ng of dexamethas one. T-2 toxin did not affect Ag transport from the challenge site to the draining lymph nodes as measured by FITC transport. However, T-2 t oxin significantly reduced both MHC class II (Ia) expression and Ag pr esentation at the same concentrations. Because T-2 toxin, a known prot ein synthesis inhibitor, was found to inhibit protein synthesis in epi dermal cell cultures as measured by [H-3]-leucine incorporation, cyclo heximide was also examined. Cycloheximide reduced both oxazolone-induc ed ear swelling and Ag presentation in a similar manner to T-2 toxin. One mechanism of action for T-2 toxin in reducing the contact hypersen sitivity response is via inhibition of protein synthesis and effective Ag presentation by epidermal Langerhans cells. This may involve alter ations in la Ag expression, although a role for class II in the induct ion phase of the contact hypersensitivity response has not been establ ished definitively.