Effect of in vivo injection of recombinant human Interleukin-2 on peritoneal macrophages from MRL-lprlpr mice

Different characteristics of peritoneal macrophages have been studied, to assess the role of macrophages in the pathogenesis of MRL-lprlpr mice which develop a lupus-like syndrome. Resident peritoneal macrophages from MRL-lprlpr mice (> 10 weeks old) displayed characteristics of activation, while thioglycollate-elicited or resident macrophages from normal mice (Balbc or MRL-+/+) did not. In addition to Ia antigens, macrophages spontaneously expressed Interleukin-2 receptors (IL2-R) whereas resident macrophages from normal mice did not. Injection of recombinant human Interleukin-2 (rHu-IL2) by the i.p. route to normal mice did not modify the cellular composition of the resident peritoneal population. On the contrary, rHu-IL2 treatment of MRL-lprlpr mice induced an enhancement in cell number in the peritoneal cavity. At the same time, macrophages harvested from treated MRL-lprlpr mice showed enhanced chemiluminescence triggered by phorbol-12-myristate-13-acetate (PMA) whereas peritoneal macrophages from treated normal mice did not. These results indicate that MRL-lprlpr peritoneal macrophages display features of selective ‘activation’ and suggest that the expression of IL2-R could be involved in the pathogenesis of inflammatory disorders seen in MRL-lprlpr autoimmunity.