PHOTOALLERGIC RESPONSES TO CHEMICALS

Abstract— –Photochemical and immunologic knowledge about photoallergy to chemicals is briefly summarized. Studies in in vitro systems have demonstrated that photoallergic compounds can covalently bond to proteins through a photochemical reaction. The immunologic nature of the photoallergic response is based mainly on clinical observations, induction of photoallergy in man and in guinea‐pigs and on results of in vitro immunologic tests. Studies of the photoreactions of the photoallergic compound, 3,3′,4′,5‐tetrachlorosalicylanilide (TCSA), with proteins are discussed. TCSA noncovalently bonds to human serum albumin prior to irradiation. Prior interaction is essential for formation of a photoaddition product indicating that a short‐lived reactive species derived from TCSA is involved in the photoaddition and limiting the number of skin proteins which can participate in antigen formation. By fragmentation of the TCSA‐albumin photoadduct with CNBr, it was determined that TCSA can bond to at least three sites on the albumin molecule. TCSA also can sensitize the photooxidation of histidine in albumin. Copyright © 1979, Wiley Blackwell. All rights reserved