Regulation of immune complexes during infection of mice with lactate dehydrogenase-elevating virus: Studies with interferon-gamma gene knockout and tolerant mice

Mice persistently infected with lactate dehydrogenase-elevating virus (LDV) develop circulating IgG-containing hydrophobic immune complexes, with a mo lecular mass of 150 to 300 kd, which bind to the surfaces of high-capacity enzyme-linked immunosorbent assay (ELISA) plates. LDV infection also stimul ates polyclonal B-cell activation and autoimmunity. For this study, interfe ron-gamma gene knockout (GKO) mice were utilized to study circulating immun e complexes and other parameters of LDV infection. The kinetics of LDV vire mia, formation of plasma IgG anti-LDV antibodies, and LDV replication in th e spleen and liver were essentially normal in GKO mice. Polyclonal activati on of B cells, as reflected by increased total plasma IgG concentration dur ing LDV infection, was found to be intact in GKO mice, although at a lower magnitude than in control mice. The plasma concentration of IgG-containing hydrophobic immune complexes was reduced about 75% in LDV-infected GKO mice relative to normal LDV-infected controls. Allogeneic tissue responses were also found to be reduced in LDV-infected GKO mice relative to those in nor mal LDV-infected controls. These results dissociate specific anti-LDV immun ity from formation of hydrophobic immune complexes, show that the IgG anti- LDV response as well as LDV replication in the spleen and liver are insensi tive to physiological levels of interferon (IFN)-gamma, and suggest that Ig G-containing immune complexes stimulated by LDV infection are a marker for autoimmunity.