Adult female Rhipicephalus appendiculatus ticks were fed on rabbits immunized with either bovine serum albumin, solubilized tick midgut membrane proteins, a 50:50 mixture of bovine serum albumin and solubilized tick midgut membrane proteins or buffer. Haemolymph harvested from these ticks after they had fed to engorgement and sera from the immunized rabbits were assayed for the presence and quantity of both the total rabbit IgG and specific rabbit IgG raised against bovine serum albumin using the enzyme linked immunosorbent assay technique. The results obtained indicated that rabbit IgG was able to cross the midgut barrier of the tick into the haemolymph. Furthermore, the amounts of IgG crossing into the haemolymph were dependent on the antibody titres in the serum. The results also showed that feeding ticks on blood containing anti-tick midgut antibodies increased the passage of IgG into the haemolymph.
