Abstract
A study was made of mycobacterial‐induced granulomas in guinea‐pig lymph nodes. Live BCG (Pasteur) induced a granuloma containing epithelioid cells while Cobalt irradiated Mycobacterium leprae induced a granuloma comprised of phagocytic macrophages. The granulomas were quantitated by measurement of lymph node weight and the areas of infiltration in histological sections. The time course of granuloma formation induced by Co‐irradiated M. leprae was very different from the time course of the granuloma formation induced by BCG. Collagen synthesis assessed by incorporation of ^14^C‐proline into collagenase sensitive protein was greater in lymph nodes draining the site of injection of Co‐irradiated BCG than those draining the site of injection of Co‐irradiated M. leprae during the first 10 weeks. Collagen synthesis was delayed in the nodes from animals injected with live BCG for at least 10 weeks. Single cell suspensions of draining lymph nodes containing granulomas consisted of lymphocytes and large cells (epithelioid cells and macrophages). A high proportion of the large cells were found to be non‐adherent in the live BCG‐induced epithelioid cell granuloma. In contrast, M. leprae‐induced granulomas contained a high percentage of adherent large cells. In both the granulomas, the majority of large cells were esterase positive and showed the presence of fibronectin. Most of the large cells in the granulomas did not carry receptors for the Fc component of IgG or the C3 component of complement and did not exhibit peroxidase activity.