Expression of Fas and Fas ligand in Hodgkin's disease.

Fas and Fas ligand expression were investigated in twenty two cases of classical Hodgkin's disease (HD) by immunohistochemistry. While Reed-Sternberg (RS) cells in 7/22 (32%) cases expressed Fas ligand, reactive lymphoid cells expressed Fas ligand in only 2 (9%) cases. In 20/22 (91%) cases, the RS cells expressed Fas. A higher proportion of RS cells in the nodular sclerosis subtype expressed Fas as compared to the mixed cellularity subtype. In 18/22 (82%) cases, Fas expression was also noted in the reactive lymphoid cells. In eight cases, the reactive lymphoid cells were also analyzed by flow cytometry and a majority of them were CD4+CD45RO+. Most of these activated T-cells expressed Fas but were negative for Fas Ligand. To investigate the co-expression of Fas and Fas Ligand in the RS cells, six cases were subjected to Fas and Fas ligand immunostaining on consecutive sections. The co-expression was documented in the RS cells in four of six cases. These six cases with expression of both Fas and Fas ligand were investigated for the incidence of apoptosis. There was no statistically significant relationship between expression of Fas on reactive cells, expression of FasL on RS cells and the proportion of apoptotic reactive cells. In all these cases apoptosis was not observed in the RS cells. Thus Fas - FasL interactions may not lead to apoptosis of the RS cells.