THE ROLE OF FOLLICULAR AND INTERDIGITATING DENDRITIC CELLS IN HIV-RELATED LYMPHOID HYPERPLASIA - LOCALIZATION OF FASCIN

Fascin is a 55-kDa, actin-bundling protein expressed in follicular and interdigitating dendritic cells (DCs). Because these cells play a piv otal role in the pathogenesis of human immunodeficiency virus-related lymphoid hyperplasias (HLP), we evaluated them in 49 cases by immunohi stochemical localization of fascin, and we related the findings to the histologic stage of disease, Fifteen cases of early HLP revealed stro ng localization of fascin within DCs of hyperplastic follicles and int ense staining in interdigitating DCs and their processes in the interf ollicular zones. Some follicles revealed focal disruption of the fasci n-positive dendritic framework. DCs were also aligned beneath the peri pheral sinuses of the node, In 15 cases of progressive HLP with partia l follicular involution, 3 cases revealed findings similar to those de scribed above, Twelve cases revealed loss of follicular dendritic stai ning, which was moderate in five cases and marked in seven. Residual c lusters of DCs remained after partial dissolution, Interfollicular den dritic staining was reduced in 13 cases, and perisinusoidal staining w as reduced in 7. In late-stage HLP, staining of both follicular and in terdigitating DCs was reduced or absent, Nine cases of diffuse immunob lastic or angioimmunoblastic lymphadenopathy-like proliferation had ma rkedly reduced or absent follicular DCs, but prominent staining was pr esent in interfollicular DCs, which formed a meshwork throughout the n ode in eight cases. Two cases of hyaline-vascular lymphoid hyperplasia had increased follicular DCs forming a tight syncytial network, In mo st cases, there was reduction of dendritic fascin-expressing cells wit h advanced disease and destruction of the dendritic framework of the n ode. Diffuse hyperplasia of fascin-positive interdigitating cells occu rred in cases with angioimmunoblastic morphologic features, and cases of hyaline-vascular lymphoid hyperplasia had increased follicular dend ritic histiocytes forming a tight syncytial network. Destruction of DC s and, in some cases, interdigitating cell hyperplasia might be associ ated with the variable clinical course of HLP.