Antigen stimulation alters the expression of S-100 protein in the giant macrophages and follicular dendritic cells of the guinea pig lymph nodes.

Injections of chick erythrocytes were employed to examine the relationship between expression of S-100 protein and antigen stimulation in the giant macrophages (GM) and follicular dendritic cells (FDC) of guinea pig lymph nodes by an immunocytochemical method. Popliteal lymph nodes were observed 1, 3, 6 and 12 h, then 1, 2 and 3 days, and finally 1, 2 and 4 weeks after injection of chick erythrocytes into hind foot pads. All GM in control lymph nodes were dendritic in shape at the cortical surface and strongly immunoreactive to S-100 protein. In lymph nodes of injected animals, three types of GM were observed at the cortical surface: cells were S-100-protein-positive/phagocytosis-positive, S-100-protein-positive/phagocytosis-negative and S-100-protein-negative/phagocytosis-positive. GM that were S-100-protein-negative/phagocytosis-positive appeared from 1 h onwards, reaching a maximum number at 6 h and then decreasing in number with time at the cortical surface. In the medulla, such cells were observed after 1 h, increasing to a maximal level at 6 h and, thereafter, gradually decreasing in number. These results indicate that expression of S-100 protein in GM is altered by antigen stimulation and that GM move in the lymph nodes. The same pattern of expression of S-100 protein was demonstrated in the FDC 1 week after injection.