Macrophages migrate from the marginal zone into the germinal centre of the rodent spleen.

In the first experiment, histological observation of the mouse spleen was carried out after intravenous carbon injection. Large carbon-laden macrophages were found in the marginal zone soon after injection and then they appeared to migrate into the white or red pulp. Macrophages migrating deeply into the white pulp came together favorably around the germinal centre and entered the majority of the germinal centres by 10 days. In the second and third experiments, syngeneic transfer of rat peritoneal macrophages labeled with carbon were performed. They were injected either retrograde via hepatic artery or directly into the splenic artery. Carbon-laden macrophages were found in the germinal centres in the spleen 12 to 24 hours after injection though in a limited number. Possible migration of intrinsic as well as extrinsic macrophage from the marginal zone into the germinal centre was demonstrated.