We could demonstrate the presence of anti-dsDNA IgE in the Lyn−/−, FcγRIIb−/− and FcγRIIb−/− × Yaa lupus-like mouse models as well as in a cohort of 42 SLE patients where their levels were associated with disease activity and especially with active lupus nephritis (Table 1) [6,32]. The gene discussed is FCGR2B; the disease is systemic lupus erythematosus.