Dermacentor andersoni: effects of repeated infestations on lymphocyte proliferation, cytokine production, and adhesion-molecule expression by BALB/c mice

The effects of repeated infestations with Dermacentor andersoni nymphs on t he lymphocyte functions of BALB/c mice were investigated. The in-vitro prol iferation responses to concanavalin-A or salivary-gland molecules, the prod uction of cytokines, and the expression of two adhesion molecules-leucocyte function-associated antigen-1 (LFA-1) and very late activation-4 (VLA-4) - were all studied. In addition, the ability of salivary-gland extract or sal iva from D. andersoni to modulate expression of lymphocyte adhesion molecul es in vitro was determined. The proliferative responses of T-lymphocytes to concanavalin-A were signifi cantly suppressed after first and second infestations, and significant incr eases in lymphocyte proliferation in the presence of tick salivary-gland an tigen were observed in infested mice. After two infestations, production of interleukin-2 was significantly decreased but that of interferon-gamma rem ained unchanged. Production of interleukin-4 and interleukin-10 was signifi cantly enhanced in infested mice after both the first and second infestatio ns. Expression of LFA-1 and VLA-4 by lymphocytes from infested mice was sup pressed. Furthermore, both a salivary-gland extract and the saliva of D. an dersoni reduced the in-vitro expression of both of these adhesion molecules by lymphocytes from tick-naive mice.