Role of the Popliteal Lymph Node in Infection with Mycobacterium marinum of the Hind Footpad of the Mouse, and Source of the Cells that Characterize the Process

We examined the possibility that the popliteal lymph node serves as the source of the lymphocytes that, together with macrophages, characterize Ihc lesion produced by infection with Mycobacterium marinum in the hind footpad of Ihc mouse. Naive mice were partially protected against challenge with M. marinum in the hind footpad by intravenous infusion of lymphoc) its harvested from the popliteal nodes of donor mice infected with M. marinum 7 days earlier. Lymphocytes harvested from the popliteal nodes of infected donors, labelled in vitro with ³H-uridine, and infused intravenously into naive mice that were immediately challenged in the hind footpads with M. marinum, localized in the popliteal nodes of the recipient mice but nol in the footpad lesions. Lymphocytes harvested from the spleens of naive donors and labelled in vitro appeared to home to the popliteal nude draining the M. marinum-infected footpad. Thus, the primary rule of the popliteal lymph node appeared to be passive trapping of the lymphocytes brought to it by the circulairon or afferent lymphatics. We then tried lo locate the sources of bolh lymphocytes and macrophages that characterize the lesion. Temporary occlusion of the abdominal aorta prevented labelling by intravenously infused ³H-thymidine (³H-TdR) of the mononuclear cells of both footpad lesion and popliteal node. Temporary occlusion of the left common iliac artery during ³H-TdR infusion prevented immediate labelling on the ipsilateral side. After 24 and 48 h, however, small numbers of labelled lymphocyles were found in the left hind footpad lesion. Amputation of the right leg at the hip joint, but run right poplitial lymphadenectomy, performed immediately after re-estublishment of patency of the left common iliac artery, prevented the late influx of labelled lymphocytes into the lesion of the left hind footpad. Thus, the chief source of both the lymphocytes and the macrophages of the footpad lesion appeared lo be the lesion ilself.