Experimental murine leprosy. 6. Cellular reactions in the draining lymph node after injection of Mycobacterium lepraemurium into the foot-pads of mice.

The reaction patterns of the draining lymph nodes were studied in C3H and C57/BL mice after foot-pad inoculation of Mycobacterium lepraemurium (MLM). Bacilli were found in the lymph nodes of both strains already a few days after inoculation, but any marked reaction did not occur until approximately 3 weeks later and then only in the lymph nodes of C57/BL mice. The reaction involved enlargement, epithelioid cell granuloma formation and proliferation of pyroninophilic blast cells in the T-cell area. The lymph nodes in these animals remained large and showed a reactive pattern for up to 230 days. At this stage, bacilli were relatively few. In C3H mice, no reactive changes developed and it was not until much later that they became significantly enlarged. In the advanced stage, normal lymph node structures were replaced completely by giant macrophages loaded with acid-fast bacilli. C3H and C57/BL mice are polar as regards the lymph node reaction against MLM; in C3H mice it resembles the advances stages of human leprosy while it in C57/BL mice mimics the situation in the BT-TT region. Immunofluorescence studies did not reveal any early proliferation of Ig-containing cells and the lack of cellular immune reaction against MLM in C3H mice cannot be explained as an early B-cell reaction to interfere with the development of cell mediated immunity.