The cellular composition of granulomas in mesenteric lymph nodes from patients with Crohn's disease.

The immunohistochemical findings in granulomatous lymphadenitis in patients with Crohn's disease are presented and compared with conventional light microscopic findings. The cellular composition of the granulomas in mesenteric lymph nodes was examined with a broad panel of monoclonal and polyclonal antibodies directed to B-cells, T-cells, monocytes/macrophages, dendritic reticulum cells, HLA-DR antigens and the transferrin receptor. The centre of the granulomas contains OKIa+, OKM1+, OKT9+, DRC-, To5- epithelioid cells and giant cells and OKT3+ lymphocytes. In general, the majority of the small lymphocytes within the granulomas expresses the OKT3+, OKT4+ Leu 3a+ phenotype which points toward T-helper cells. Fewer OKT3+ OKT8+ T suppressor/cytotoxic cells are observed. At the periphery of the granulomas a lymphocytic corona composed of BA1+, B1+ B lymphocytes may be present. From these findings it can be concluded that the granulomas in mesenteric lymph nodes from patients with Crohn's disease are composed of centrally located T-lymphocytes and of epithelioid cells which are of monocyte/macrophage origin and have the characteristics of antigen-presenting cells.