ALTERATIONS IN FASCIN-EXPRESSING GERMINAL CENTER DENDRITIC CELLS IN NEOPLASTIC FOLLICLES OF B-CELL LYMPHOMAS

Germinal center dendritic cells (GCDCs) have essential functions in re tention of immune complexes within secondary follicles, B-lymphocyte a ntigenic stimulation, B-cell activation, homing of B-cells via adhesio n molecules such as ICAM-1 and VCAM-1, and B-cell survival via apoptos is, The neoplastic cells of follicular lymphomas (FLs) are thought to derive from follicular B lymphocytes, but their relationship to GCDCs remains unclear, This study used immunohistochemical staining for fasc in, a 55-kDa actin-bundling protein strongly expressed in GCDCs and th eir processes, to evaluate their distribution in neoplastic follicles, Forty-two cases of B-cell FL were evaluated, and immunoreactive stain ing for fascin was compared with six cases of Castleman's disease (CD) and six cases of follicular hyperplasia. FLs generally revealed decre ased or absent fascin-staining GCDCs, suggesting loss of fascin expres sion by dendritic cells in neoplastic follicles compared with hyperpla stic follicular centers, In some follicles, there was partial retentio n of dendritic architecture with islands of residual syncytial network , Interdigitating reticulum cells in the parafollicular regions reveal ed normal fascin expression with intense staining of dendritic process es. In contrast with FLs, cases of follicular hyperplasia revealed nor mal or increased fascin-positive follicular dendritic cells, and in ca ses of hyaline vascular CD, follicular dendritic cells revealed tight syncytial networks, These results suggest that GCDCs are deficient in neoplastic follicles, compared with benign reactive or hyperplastic fo llicles. This alterations in the germinal center micro-environment mig ht explain the inability of FL cells to present antigen to T lymphocyt es and to mount an effective antitumor immune response.