Morphological interactions of interdigitating dendritic cells with B and T cells in human mesenteric lymph nodes.

Interdigitating dendritic cells (IDC) of the human mesenteric lymph nodes (LN) were examined by two-color immunofluorescent microscopy and flow cytometry to clarify their exact localization, immunophenotype, and relationships with T and B cells. IDC were identified as HLA-DR(bright) large dendriform cells of the T cell areas co-expressing CD40, CD54 (ICAM-1), CD80 (B7/B7-1), CD83, and CD86 (B70/B7-2). The majority of IDC directly attached to a few IgD+ naive B cells as well as to numerous CD4+ T cells. When LN cells were singly suspended and briefly incubated in vitro, IDC formed clusters with IgD+ IgM+ naive B cells, but not with IgA+ or IgG+ B cells. When suspended LN cells were cultured, clustered B cells disappeared within 7 days, and on prolonged culture, some IDC developed into extensively dendriform cells forming stable complexes with several or sometimes numerous CD4+ IL-2R+ CD40L+ activated T cells. These findings indicate that resting naive B cells actually interact with IDC directly in T cell areas of human secondary lymphoid tissues. IDC have a non-antigen (Ag)-specific, strong affinity for resting naive B cells, but this affinity is transient and IDC cannot form stable complexes with B cells, although they can form stable complexes with activated T cells. It is suggested that the stable IDC/Ag-activated T cell complexes make it possible to capture and to stimulate rare Ag-specific resting naive B cells with high efficiency.

Malignant fibrous histiocytoma of the right ventricle of the heart.

Right-sided cardiac malignant fibrous histiocytoma (MFH) is extremely rare, and to the authors' knowledge only three cases have been reported. In this study, a case of MFH in the right ventricle, the septum, and the pulmonary valves and artery in a 47 year old male is described. The tumor showed typical pathological features of MFH, such as cellular pleomorphism, storiform pattern and abundant mitoses. Immunohistochemical and electron microscopical findings were compatible with MFH, and excluded the possibility of leiomyosarcoma and angiosarcoma. Whole body examination, including Gallium scintigram, localized the primary site to the heart. The details of this case are presented with a review of the reported cases of cardiac MFH.