Induction of focal hemopoiesis in adult rat liver by glucan, a macrophage activator. A cytochemical and ultrastructural study.

Multiple injections of glucan, a beta-1,3-polyglucose with a potent stimulating effect on the mono-nuclear phagocytes, induced hemopoiesis in adult rat liver. Hemopoietic islands were present in the connective tissue of the portal triads and in the perisinusoidal spaces. The use of peroxidase cytochemistry facilitated the detection of such islands at the light microscopic level and the identification of their cellular components at the ultrastructural level. The hemopoietic colonies consisted of erythroid and myeloid series. The erythropoietic cells comprised erythroblasts, normoblasts, and reticulocytes, all of which contained peroxidase reaction product diffusely in their cytoplasm. The granulopoietic series consisted of promyelocytes (peroxidase activity in nuclear envelope, endoplasmic reticulum, Golgi apparatus, and granules) and myelocytes (peroxidase only in granules). The hemopoietic islands were always associated with macrophages which exhibited peroxidase activity in NE and endoplasmic reticulum but not in the Golgi apparatus. This association between hemopoietic cells and "glucan-activated" macrophages shows the central role of macrophages in differentiation of hemopoietic stem cells and suggests that the macrophage-activating potency of glucan and its effect on hepatic hemopoiesis are interrelated.