Characterization of resident peritoneal cells in MRL mice

Detection of cell surface markers and cell surface receptors of resident peritoneal cells in MRL/Mp-1pr/1pr (MRL/1) and MRL/Mp-+/+ (MRL/n) mice was made by cytotoxic assay using anti-Thy1.2 and anti-IAk or anti-IE antibodies and rabbit anti-sheep red blood cell IgG coated sheep erythrocytes, respectively. MRL/1 mice showed a remarkable increase in the number of peritoneal cells, the main cells of which were not macrophages but T-cells. The cell surface Fc gamma-receptors on the peritoneal macrophages increased and their immune phagocytosis mediated by Fc gamma-receptors was enhanced. Ia expression of the macrophages showed a high value from in early life, but decreased at the end of life. On the contrary, MRL/n mice showed a low value in early life, which then increased after 15 weeks and continued at a high value until 25 weeks, the end of the experimental period. We described the characteristic increment of T-cells in the peritoneal cavity of MRL/1 mice and discussed the relationship between Ia expression and development of autoimmune symptoms in MRL/1 and MRL/n mice.