Given that the intestinal IgA response was altered in Bank1-/- mice, yet the frequency of IgA-coated bacteria remained comparable between Bank1-/- and WT mice both in steady state and during lupus, we reasoned that the binding pattern of the gut-secreted IgA to fecal bacteria might diverge between Bank1-/- and WT mice. The gene discussed is BANK1; the disease is systemic lupus erythematosus.