Lymphocyte subtypes in experimentally induced early-stage bovine tuberculous lesions

The identity of the lymphocyte subtypes constituting the lymphocytic mantle within developing early-stage lesions of bovine tuberculosis was investigated immunohistochemically in calves inoculated intranasally with 2 x 10(7) colony-forming units of a field isolate of Mycobacterium bovis. Pulmonary lesions were examined 7, 14, 21, 28 and 42 days after inoculation, and bronchial lymph node lesions at 35 days. The immunolabelling results reported were obtained with monoclonal antibodies against two T-cell epitopes (WC1+ gamma delta and CD2+) and against B-cell epitopes. Large numbers of CD2+ T-lymphocytes were observed around developing areas of necrosis throughout the study; WC1+ gamma delta cells, however, were more numerous at these sites up to and including day 21. On the other hand, aggregates of B lymphocytes did not become prominent in areas adjacent to lesions until day 42. The results suggest that these lymphocyte phenotypes play a role in the pathogenesis of early-stage lesions.