Macrophage lineage in the rat liver with special reference to Ia-antigen expression

Specific cellular subpopulations in the liver were stained with monoclonal antibodies that recognized monocytes/macrophages (EDI), tissue macrophages (ED2), MHC class II (Ia) antigen (MRC OX6), and dendritic cells/gamma,delta T-cells (MRC OX62). The majority of ED1+ cells and ED2+ cells were found in the hepatic lobule, whereas OX6+ cells and OX62+ cells were mon densely distributed within the Glisson's sheath than in the hepatic lobule. The distributional density of ED1+ cells, ED2+ cells, OX6+ cells, and OX62+ cells in the hepatic lobule was approximately 6 :4: 1:0.1 and that in the portal area was 5 :2 : 20 : 0.3. About 17% of ED1+ cells were immunostained for OX6 in the hepatic lobule and half of them were stained for OX6 within the Glisson's sheath, whereas ED2+OX6+ cells were scarcely detected. OX6+ cells were classified into two different types from their ultrastructures. The first type (type I) extended lone cytoplasmic processes and were endowed with well-developed lysosomal system. The other (type II) had characteristic short cytoplasmic processes, which was characterized by inconspicuous lysosomal system and frequent hyaloplasm. I hr after intravenous injection of latex particles, some of OX6+ cells (type I) ingested these particles, but the other (type IT) did not. OX62+ latex-laden cells were not detected at an ultrastructural level. These results indicate that the non-treated rat liver may contain several different populations of macrophages.