Effects of cyclosporin A on humoral immunity to ticks and on cutaneous immediate and delayed hypersensitivity reactions to Ixodes ricinus L. salivary-gland antigens in re-infested rabbits.

When rabbits are repeatedly infested with Ixodes ricinus L. adults, they acquire resistance to these ticks. A humoral response occurs and the skin of the host becomes progressively sensitized to the saliva of the ectoparasites. The present study examined the effects of cyclosporin A on these two aspects of immunity in re-infested rabbits. Using the enzyme-linked immunosorbent assay (ELISA), moderate suppression of the secondary IgG response to bites of these ticks was observed in animals given this immunosuppressive drug. The agent blocked the immediate cutaneous (type I) reaction normally developed in response to the intradermal injection of I. ricinus salivary gland antigens, as detected by measuring the skinfold thickness. The same method revealed a decreased delayed (type IV) hypersensitivity to these antigens. The present experiments demonstrate the major role of cyclosporin A-sensitive cells (mostly T-lymphocytes, mast cells and basophils) involved in the complex phenomenon of resistance to ticks.