CAPRINE HAEMONCHOSIS - LYMPHOCYTE-RESPONSES TO PARASITE ANTIGEN AND MITOGENS

In vitro proliferative responses of blood lymphocytes to parasite antigen and to T cell (phytohaemagglutinin) and B cell (lipopolysaccharide) mitogens were measured as indicators of immune responsiveness in worm-free and trickle-infected goats challenged with Haemonchus contortus. Lymphocytes from worm-free goats displayed marked lymphocyte-responsiveness to parasite antigen indicating inherent ability of goat lymphocytes to recognise it. Pre-challenge stimulation indices of trickle-infected goats were higher than those of worm-free goats suggesting the presence of antigen-sensitive cells in the blood. Following challenge infection, lymphocytes from trickle-infected and worm-free goats showed enhanced responsiveness to H. contortus antigen on day 9. However, as infection progressed further, lymphocyte responses to parasite antigen became significantly (P < 0.05) suppressed in all groups and remained so until day 28. Interestingly, lymphoproliferative responses to T and B cell mitogens remained unaffected during infection and there was no significant difference in the stimulation indices between trickle-infected and worm-free goats. © 1991.