Hepatic reticuloendothelial system activation in autoimmune mice: differences between (NZB X NZW)F1 and MRL-lpr/lpr strains.

5'-Nucleotidase (5'N) activity and Ia expression of hepatic nonparenchymal cells (NPCs) of the autoimmune (NZB X NZW)F1 and MRL-lpr/lpr and nonautoimmune C3H/FeJ, DBA/2J, and A/J strains were assayed to determine endogenous activation of the hepatic reticuloendothelial system (RES). Pretreatment of the nonautoimmune strains with Corynebacterium parvum resulted in decreases in Fc receptor expressor and 5'N and an increase in Ia expression of NPCs. Endogenous hepatic RES activation, as measured by low 5'N and high Ia expression, was observed in both the autoimmune MRL-lpr/lpr and (NZB X NZW)F1 strains even without C. parvum pretreatment. However, in the MRL-lpr/lpr strain, age is a dependent variable in activation and correlates with delayed clearance from the circulation of soluble IgG immune complexes. In the (NZB X NZW)F1 strain, the observation of decreased 5'-nucleotidase activity and increased percentage of Ia-positive cells at all ages suggests a primary abnormality. Therefore, different genetic or exogenous factors may be responsible for the activation of the hepatic RES in these autoimmune strains.