COMPARISON OF LOCAL AND SYSTEMIC RESPONSIVENESS OF LYMPHOCYTES IN-VITRO TO BOVICOLA OVIS ANTIGEN AND CONCANAVALIN-A IN B-OVIS-INFESTED AND NAIVE LAMBS

The in vitro proliferation assay was used to determine lymphocyte resp onsiveness to soluble antigen of B. ovis and to Concanavalin A (Con A) in peripheral blood, spleen and various lymph nodes from B. ovis-infe sted and naive lambs. From March to July, an assay of monthly blood sa mples showed generally higher proliferative responses to antigen and C on A in B. ovis-infested than naive-lambs. The proliferative response of cells from the skin-draining prescapular lymph nodes to B. ovis ant igen was significantly higher in B. ovis-infested than naive lambs. Re sponses of cells from the medial iliac, mediastinal and mesenteric lym ph nodes (which do not receive lymph from the skin) and spleen showed no significant differences between groups. Within the B. ovis-infested lambs, the response of cells from the prescapular lymph node was sign ificantly higher than that from any other lymphoid organ examined. Res ponsiveness of the prescapular, medial iliac and mesenteric lymph node and spleen cells to Con A was not significantly different between gro ups, while mediastinal lymph node cells showed a significantly higher response in B. ovis-infested lambs. The data indicate that the antigen -specific cellular immune response is operating mainly locally, at the level of the skin and draining lymph nodes. Responses to the T cell m itogen Con A did not support non-specific immunodepression as reported in other ectoparasite/host systems.