(A) Activation of PYK2 in PBMCs from healthy donors (n = 24) and SLE patients with central nervous system (CNS) disease (n = 6), WHO class IV nephritis (n = 29), or nephritis other than WHO class IV (n = 19). Total proteins obtained from PBMCs lysates were examined by Western blotting analysis for p-PYK2 as indicated in patients and methods. Lane 1, healthy donors;Lane 2, SLE patients with central nervous system; Lane 3, lupus nephritis other than WHO class IV;Lane 4, lupus nephritis IV. (B) The ratio between the optical density of specific bands and β-actin of the same sample was calculated and expressed graphically. The experiments for each sample were repeated at least three times and bars represent the mean and standard deviation of three separate experiments. Statistical comparison of all groups was made with healthy donors. The significance level was set at* = P < 0.05. (C) Correlation between PYK2 activation in PBMCs and serum levels of CH50 in SLE patients (n = 36).