EFFECTS OF HUMAN RECOMBINANT INTERLEUKIN-2 ON RESISTANCE, AND ON THE HUMORAL AND CELLULAR-RESPONSE OF RABBITS INFESTED WITH ADULT IXODES-RICINUS TICKS

Rabbits were treated with subcutaneous injections of ten doses of 5 X 10(3) units of human recombinant interleukin-2 (IL-2) during a first i nfestation with five adult pairs Ixodes ricinus per rabbit, while untr eated controls were infested by either five (direct control) or 25 pai rs (resistant control) per rabbit. During the second infestation with 25 pairs per rabbit in each group, rabbits treated with IL-2 became mo re resistant than the rabbits in the two untreated control groups. Str onger resistance was manifested by lower engorgement and egg laying we ights, and by smaller numbers of normally fed or ovipositioning ticks. IL-2 treatment had no significant effects on the rabbit anti-tick ant ibody production and the lymphocyte proliferation to a salivary gland extract (SGE). By contrast, the highest cutaneous responses to SGE wer e observed in the IL-2 treated group. IL-2 may increase rabbit cell-me diated immunity, and stimulate an increase in the production of memory cells during the induction phase of the immune response (first infest ation), allowing the development of a strong resistance in lightly inf ested rabbits.