Autoantibody responses are equally strong in wild-type and AE^−/− NZB mice. Comparison of number of IgG molecules of each isotype present on RBCs from individual wild-type (n = 16) or AE^−/− (n = 6) NZB mice aged 20 weeks. The IgG levels were measured by DELAT. The background levels on the RBCs of healthy control mice are less than 380 molecules IgG₁, less than 250 molecules IgG_2a, less than 280 molecules IgG_2b, and less than 500 molecules IgG₃.