Immunology of interactions between ticks and hosts

Abstract

Abstract Infestation with ixodid tick stimulates the immune regulatory and effector pathways of the hosts involving antigen presenting cells, T‐lymphocytes, B‐lymphocytes, basophils, mast cells, eosinophils and a variety of bioactive molecules like cytokines, antibodies and complement. Tick‐mediated immunosuppression has been investigated using cells derived from infested animals and by exposing cells from uninfested animals to tick salivary gland molecules. Tick‐induced suppression of host immune defences is characterized by reduced ability of lymphocytes from infested animals to proliferate m vitro in the presence of concanavalin A (Con A), diminished primary antibody responses to T‐cell dependent antigen, and decreased elaboration of macrophage (IL‐1 and TNF‐α) and Th 1 ‐lymphocyte cytokines (IFN‐γ), whereas Th2 cytokines production (IL‐4, IL‐5 and IL‐10) isenhanced. It is known that IL‐10 inhibits Thl cell development and also reduces the in vitro T‐lymphocyte proliferative response to Con A stimulation. Proteins which inhibited T‐lymphocyte in vitro responsiveness to Con A were also isolated from tick salivary glands.