PRE-KUPFFER LIKE CD4/CD8 DOUBLE-POSITIVE MONONUCLEAR-CELLS PRESENT IN RAT-LIVER

Nonparenchymal cells isolated from Fischer rat liver were separated into subpopulations by passage through a nylon wool column and/or culturing in a plastic plate. Besides typical Kupffer cells, we detected a unique population of cells (called PKu cells) which were plastic adherent but did not spread on a short term culture, were nonadherent on nylon wool, and were nonphagocytic, as opposed to Kupffer cells. Both Kupffer cells and PKu cells expressed CD4 (recognized with W3/25 mAb), CD8 (OX-8), a NK cell antigen (3.2.3), and a monocyte antigen (OX-41), as assessed by dow cytofluorometry. However, the proportion of cells bearing high densities of CD8 and 3.2.3 antigens was much larger for PKu cells than for Kupffer cells. Reverse transcriptase-PCR analysis of CD8 mRNA revealed that PKu cells expressed the CD8 alpha chain but not the beta chain. When PKu cells were treated with phorbol 12-myristate 13-acetate (PMA), they exhibited spreading and phagocytic activities, and showed a similar morphology to Kupffer cells in the spread form. Moreover, PMA treatment decreased the high density of CD8 antigen on PKu cells. These findings indicated that PKu cells present in normal rat liver are precursors of Kupffer cells.