Immunohistological study in the distribution and function of follicular dendritic cell(FDC) in follicular lymphoma.

Follicular dendritic cell (FDC) is an unique cell type locating in normal or reactive lymph follicle and forming a reticular framework by their dendritic cytoplasmic processes. FDC has a special ability to capture and retain antigens in the form of immune complexes on their surface and it is believed that it may play important roles in immune response. Recent papers have indicated that FDCs are also present in the neoplastic follicles of follicular lymphomas. Their features, however, are still unclear. In the present study, the immunohistochemical and electron microscopic examinations of FDCs in the neoplastic follicles of 11 cases of follicular lymphoma were performed to elucidate their functional significance in this kind of neoplasia. These results were also compared with FDCs in the reactive (non-neoplastic) follicles and the stromal cells in diffuse follicular center cell lymphomas including the cases which were diagnosed as follicular lymphoma previously or pseudo-nodular lymphoblastic lymphoma.The findings obtained from this study are summarised as following: 1) FDCs in follicular lymphoma revealed almost the same ultrastructual features and antigenic phenotypes as those in reactive follicle, 2) some of them appeared to have the immune complex trapping ability, 3) DRC-1+stromal cells were present focally or vestigially in diffuse lymphoma but no distinct immune complex trapping ability was defined on these cells, even in the case developing from follicular lymphoma, and 4) no DRC-1+ cells were detected in the pseudonodular lymphoblastic lymphoma. These findings suggested that the presence of FDC or related cells might be related to B-cell growth and functional FDC might be changing the form and functional properties during the progression from follicular lymphoma to diffuse lymphoma.