Figure 2.
Normal B cell homing, yet impaired formation of organized follicles in lymph nodes of mice lacking either TNF or the p55TNF-R. Cryostat sections of inguinal lymph nodes from wild-type, TNF knockout, and p55TNF-R knockout mice were analyzed by immunoperoxidase staining, developed with diaminobenzidine, and counterstained with hematoxylin. Staining with antibody to IgM shows a normal localization of B cells in the outer cortex of lymph nodes from TNF or p55TNF-R knockout mice (arrowheads); however, in contrast to wild-type mice, they are not organized into follicles but form a thin layer covering the cortex area. A similar distribution of B cells was observed by staining with anti-B220 or anti-IgD antibodies (not shown). FDC networks identified here with the FDC-M2 mAb are observed to form within follicles in wild-type but not in TNF- or p55-deficient lymph nodes. Additional staining with FDC-M1 failed to detect any FDC networks in lymph nodes from TNF or p55 knockout mice (not shown). In contrast, T cells visualized here with anti-CD3 mAb and N418+ DC (arrows) appear to develop normally in lymph nodes from these mice. Similar results were observed in mesenteric lymph nodes. F, B cell follicles; T, T cell-rich areas. (×20; ×100 for N418 staining).