RELATION OF FOLLICULAR DENDRITIC RETICULUM CELLS TO REED-STERNBERG CELLS OF HODGKINS-DISEASE WITH EMPHASIS ON THE EXPRESSION OF CD21 ANTIGEN

Based on observations of 66 cases, in which tissues were specially pro cessed to optimize the simultaneous preservation of cell membrane anti gens and morphology, we provide evidence in favor of a relationship be tween follicular dendritic reticulum cells (FDRC) and Reed-Sternberg ( RS) cells of Hodgkin's disease (HD) other than the lymphocyte predomin ance subtype. RS cells were intimately related to the FDRC network (75 % of cases), and the expression of CD21 antigen was frequent (41% of c ases). Exclusive expression of CD21 antigen was found in 11 cases of H D, while the expression of other B-cell-associated markers (CD19, CD20 , CD22) was both variable and inconsistent. The expression of T-cell a ntigens (CD3, CD4, CD8) was rare. Null phenotype of RS cells was obser ved in 27 of 66 cases (41%). Epstein-Barr virus (EBV) nucleic acids we re found in 34 of 66 (51.5%) cases. Double labeling techniques showed the presence of EBV-positive RS cells within the FDRC network A non-B- cell origin of RS cells was supported by the differential expression o f EBV latent antigens in HD (latent membrane protein+, EB nuclear anti gen 2-), which is unusual in EBV-driven lymphoblastoid cell lines and EBV-positive B-cell lymphomas. FDRC and RS cells are known to share mo rphological traits (binucleated cells), and both cell types possess Fc receptor for IgG. The hypothesis is further backed by the findings of CD15 antigen expression by occasional RS-like dysplastic FDRC in Cast leman's disease (five cases), which is characterized by hyperplasia of FDRC Whether FDRC might be the only cells involved in the conversion to RS cells by the loss or gain of antigens remains to be determined.