Immune serum transfer of cutaneous basophil-associated resistance to ticks: mediation by 7SIgG1 antibodies.

Abstract Guinea pigs acquired resistance to Amblyomma americanum larval ticks after one infestation, resulting in 46% tick rejection when challenged. Intravenous transfer of immune serum from twice-infested hosts to naive animals conferred a significant level of immunity resulting in 18 to 30% tick rejection. The minimum effective dose of serum was 3 ml per recipient, and heating the serum at 56 degrees C for 4 hr had no effect on serum activity. Fractionation of whole immune serum by gel filtration chromatography (Sephadex G-200) and ion -exchange chromatography (DEAE) demonstrated resistance activity to be in the IgG- and IgG1-containing fractions, respectively. Passage of whole immune serum through a heavy chain-specific rabbit anti-guinea pig IgG1 affinity column removed anti-tick activity and decreased the cutaneous basophil response to tick feeding by 70% in recipients. The ability to transfer both resistance to tick feeding and a significant cutaneous basophil response was eluted from the affinity column with 0.2 M Na2CO3, pH 11.5. In addition, immune serum raised against larval Ixodes dammini ticks, but not larval Rhipicephalus sanguineus ticks, was also effective at reducing feeding by larval Amblyomma americanum ticks, indicating that antibodies mediating resistance can be cross-reactive with antigens of different tick species and genera. This study demonstrates that IgG1 antibodies are responsible for the ability of immune serum to transfer cutaneous basophil-associated immune resistance against tick feeding in guinea pigs.