Baseline serum antibody levels are unperturbed in Stat3^fl/flCD19^Cre/+ mice. Preimmune serum was taken from Stat3^fl/flCD19^+/+ (Wt) and Stat3^fl/flCD19^Cre/+ (KO) mice and ELISAs were performed for baseline IgM, IgG1, IgG2a, IgG2b, and IgA secretion. • indicates Wt mice; ○, KO mice. Each circle represents one mouse.