Bovine homocytotropic antibody in the sera of cattle resistant to infestation with Rhipicephalus appendiculatus.

The homologous skin sensitizing activity of serum from tick-naive cattle (Bos taurus) and from cattle resistant to the tick Rhipicephalus appendiculatus was tested by attempting to induce passive cutaneous anaphylaxis (PCA) in tick-naive calves. The serum from tick-resistant cattle induced PCA, whereas that from tick-naive cattle failed to do so. The PCA was more marked at 72 hours than at 24 hours after administration of the serum. Treatment of the serum by heat at 56 degrees C for 2 hours or by adding 0.1 M 2-mercaptoethanol to it reduced its ability to sensitize. Serum from tick-resistant cattle did not sensitize the skin of heterologous species, namely rabbits, guinea-pigs and rats.