Cutaneous basophil responses and immune resistance of guinea pigs to ticks: passive transfer with peritoneal exudate cells or serum.

Abstract Resistance to infestation by larval Amblyomma americanum or Rhipicephalus sanguineus ticks was transferred to naive guinea pigs with peritoneal exudate cells (PEC) or serum from donors immunized by prior infestation with homologous tick larvae. In the A. americanum system, PEC transfer induced 87% tick rejection, which was similar to the level of resistance in actively sensitized hosts. In the R. sanguineus system, PEC conferred resistance (39% rejection) that was weaker than in actively sensitized hosts (57% rejection). In both systems, immune serum conferred significant but weaker resistance (20 to 29% rejection). In actively sensitized hosts, resistance to each tick species was specific, but there was considerable cross-reactive resistance. Basophils dominated the 24-hr challenge feeding sites of A. americanum ticks in actively sensitized hosts (69% of the infiltrate) and recipients of sensitized PEC (69%). Mononuclear cells were dominant (69% of the infiltrate) in the challenged tissues of immune serum recipients that had a significant but weaker cutaneous basophil response (24%). Mononuclear cells also dominated (58% of the infiltrate) the 24-hr challenge feeding sites of R. sanguineus ticks in actively sensitized hosts, but there were also 24% basophils. These studies demonstrate that immune resistance to tick is dependent on sensitized lymphoid cells or serum components, and that sensitized cells or serum can transfer a cutaneous basophil response that is associated with immune resistance. Rejection of ticks is usually associated with large basophil infiltrates, but sometimes mononuclear cells are dominant. Thus, immune resistance of guinea pigs to ticks is a heterogeneous response in which immune cells and serum probably act to recruit diverse effector leukocytes to mediate rejection that is specific but significantly cross-reactive.