Effects of ultraviolet irradiation on the acquisition and expression of tick resistance in guinea-pigs.

In guinea-pigs it has been shown that resistance to ticks is an acquired, immunologically mediated phenomenon. It has been suggested recently that epidermal Langerhans cells (LC) may play roles in the mechanisms of resistance to ticks. The ATPase-positive epidermal LC of guinea-pigs have been shown to be depleted for a period of several days following u.v. irradiations. In this study, u.v. treatment of guinea-pigs' ears before primary tick infestations resulted in a significant reduction of acquired resistance to ticks. When u.v. treatments were applied to resistant animals prior to the challenge infestations, a marked reduction in expression of resistance to ticks was demonstrated. These results can be interpreted to imply that functional LC in the epidermis are required for both the normal acquisition and the expression of the guinea-pig's immune responses to D. andersoni infestations.