ORIGIN OF MACROPHAGES IN CENTRAL NERVOUS-TISSUE - A STUDY USING INTRAPERITONEAL TRANSPLANTS CONTAINED IN MILLIPORE DIFFUSION-CHAMBERS

Abstract

In order to determine the origin of brain phagocytes brain slices and optic nerve segments from adult Lewis rats were transplanted into the peritoneal cavity of syngenic recipients. The specimens were contained in Millipore(R) diffusion chambers fitted with membranes of either 0.22 or 5.0 mum pore size. This either blocked or allowed the access of non-resident cells. Each recipient rat recieved both a 0.22 and 5.0 mum pore chamber. Later (3-16 days) the specimens were recovered and analyzed by monoclonal antibody techniques and electron-microscopy. Endothelia, GFAP+ astrocytes, ED1-/ED2+/RCA-1+/OX-6- perivascular cells and ED1-/ED2-/RCA-1+/lysozyme - microglia were found to have survived the procedure. Cells of the macrophage phenotype (ED1+/ED2+/RCA-1+/lysozyme+/vimentin+ with phagocytic vacuoles), however, were only found in large numbers in specimens kept within 5.0 mum pore size chambers, giving access to non-resident cells, and were exceedingly rare in specimens from 0.22-mum pore chambers. It has been concluded that the majority of brain phagocytes found after lesions do not originate from microglia or perivascular monocytic cells, but rather from invading cells.