Inhibition of Btk limits increase of IgM isotype autoantibodies and results in decrease of IgG isotype autoantibodies in B6.Sle1.Sle3 mice. The indicated autoantibody ELISAs were performed on sera routinely isolated from mice either treated with PCI-32765 or vehicle. All values are the optical density (OD) readings at 405 nm wavelength. Thick grey dashed line indicates vehicle, black line indicates PCI-32765. Thin dashed line indicates serum antibodies in 2-month-old lupus-resistant B6 sample indicative of negative control. All data points represent the mean ± standard error of the mean. *P < 0.05. Samples were compared by two-tailed Student's t-test with Welch's correction. D0, day zero, D28, day 28; D56, day 56.