Induction of photoallergy in guinea-pigs by injection of photoallergen-protein conjugates.

Photoconjugates were prepared by ultraviolet irradiation of guinea-pig albumin (GPA) with the photoallergens tetrachlorosalicylanilide (T4CS) and fentichlor. Injections of T4CS-GPA induced photoallergy to T4CS in 11 of 12 guinea-pigs whereas injections of fentichlor-GPA induced photoallergy in 5 of 12 guinea-pigs. Thus the fentichlor-GPA photoconjugate, which contained a molar ratio of hapten to protein 3 times higher than the corresponding T4CS conjugate, produced a significantly lower response. The results demonstrate the importance of protein conjugate formation in the induction of photoallergy, i.e. the role of carrier protein in contact sensitivity. The high potency of the T4CS-GPA photoconjugate in inducing photoallergy suggests that albumin may have a special role as a carrier protein in T4CS photoallergy.