Abstract
A study of acquired resistance in rabbits to larvae and nymphs of Rhipicephalus appendiculatus Neumann showed a positive correlation between the levels of γ globulin in the serum and the resistance developed by the host. A negative correlation between the weight of engorged ticks and γ globulin levels was also demonstrated during this study. Repeated infestations with ticks evoked a typical antibody response to antigenic challenge. The levels of γ globulin stabilized after three infestations and no further decrease in the weight of ticks was observed. The mechanism of the acquisition of resistance by the rabbits, the production of antibodies and the involvement of complement are discussed.