IMMUNOSUPPRESSION AND CYTOKINE PRODUCTION IN MICE INFESTED WITH IXODES-RICINUS TICKS - A POSSIBLE ROLE OF LAMININ AND INTERLEUKIN-10 ON THEIN-VITRO RESPONSIVENESS OF LYMPHOCYTES TO MITOGENS

T cells from BALB/c mice infested 9 days before with Ixodes ricinus ny mphs had a suppressed response to in vitro concanavalin A (Con A) stim ulation compared to cells from uninfested mice. When laminin (the main component of the extracellular matrix) was used as a coating agent, t he Con A response of naive mice was characterized by a decrease in cel l proliferation, whereas there was no significant effect on the mitoge n response of cells from infested mice. In contrast, an increased resp onse to lipopolysaccharide (LPS) was observed when assaying lymph node cells of infested mice, probably reflecting an increase in B-lymphocy te number or activity. LPS cell stimulation was not modified by lamini n. Supernatants of lymph node cells, taken 9 days after the first infe station of mice, stimulated with Con A in vitro, contained interleukin -10 (IL-10) but no significant levels of IL-5 as tested by enzyme-link ed immunosorbent assay. At this stage of the infestation all T cells r eactive with tick antigens generated in lymph nodes that drain the tic k fixation site, were CD4(+) cells, as determined by CD4(+) depletion. With cells taken 9 days after the third infestation an increase of IL -5 and IL-10 was observed. The IL-10 levels were higher than the IL-5. According to these observations, we conclude that the reduction of T- cell proliferation in response to Con A observed in lymph node cells f rom infested mice, may be due to the combined effect of laminin intera ction with T lymphocytes during migration and IL-10 production by thes e lymphocytes.