In the absence of MZMs systemic autoimmunity is accelerated in SLE-prone mice. Four-week-old female lupus-prone B6.fcgr2b^−/− mice were injected with the indicated amounts of CLs in a final volume of 200 μL once a week for a period of 2 months. At the experimental end point sera was collected and assessed for the spontaneous development of serum ANA reactivity (A) or IgG autoantibodies against dsDNA (B) as described in “Autoantibody detection.” (C) Kidney from female B6.fcgr2b^−/− mice treated as in panel A with 167 μg of CLs or an equivalent amount of PBSLs were snap-frozen, and 5-μm sections were stained with anti–mouse IgG FITC to determine the extent of IgG immune complex deposition. Image magnification 20×. (D) Four-week-old female B6 and B6.fcgr2b^−/− mice were intravenously administered 167 μg of CLs or equivalent PBSLs once a week for a period of 6 months. Sera were collected at the indicated time points and assessed for anti-dsDNA IgG reactivity as described. For all experiments, n = 5 mice/group; *P < .05 and **P < .01 as determined by the unpaired Student t test. These experiments were repeated at least twice with similar results.