Effect of giant hepatomas on lymphocyte production and secretion of apoptosis-related proteins in the rat spleen

The effect of extremely large hepatomas on splenic lymphoid elements and ap optosis-related proteins in rats were studied. Hepatoma cells were inoculat ed subcutaneously into 6-week-old rats, and 4 months later the quantities o f T and B cells, macrophages, and cells positive for Fas, Fas ligand (FasL) and interleukin-2 (IL-2) were immunohistochemically evaluated in spleens. Grafting of hepatoma cells caused hyperplasia of the spleen and development of giant tumors that could reach one-third of the rat's body weight. A 7-f old increase in the weight of the spleen was mainly due to proliferation of B lymphocytes and macrophages in the red pulp, while the relative quantity of CD4(+) and CD8(+) T cells decreased. Extremely small amount of Fas(+) a nd FasL(+) lymphocytes were present in the marginal zone, the follicles, re d pulp, and occasionally in the PALS. All the splenic zones were abundant w ith IL-2(+) cells, while macrophages and siderophages were present mainly i n the red gulp and in the marginal zone of the white pulp. We suggest that all these changes are compensatory processes of the host's lymphatic system .