Surface morphology of the central macrophages of erythroblastic islets in the spleen of aged and pregnant mice: an immunohistochemical light microscopic study.

This study used 100-mum thick paraffin sections stained by the ER-HR3 antibody to examine the three-dimensional surface morphology of the central macrophages of erythroblastic islets in the splenic red pulp of aged and pregnant mice. The ER-HR3-positive cells were the macrophages located at the center of the erythroblastic islets, and the number per unit of splenic area was almost constant until 30 days of age, thereafter showing a marked decrease. In pregnant females, the ER-HR3-positive macrophage number significantly increased and became approximately eight times higher than the control value. In aged virgin females, the islet macrophages were generally ovoid in cell profile, and shallow cup-shaped dents were formed on their cell surface. However, in pregnant females, the macrophages became larger in size, and cell socket structures, formed by long finger-like cytoplasmic processes, became prominent on their cell surface. The 3-D images, obtained from 100-mum thick paraffin sections, provided the clear morphological evidence of the activity of the islet macrophages in spleen erythropoiesis.