Stat3^fl/flCD19^Cre/+ mice are able to form IgG⁺ memory B cells. (A) Splenocytes from Stat3^fl/flCD19^+/+ (Wt) and Stat3^fl/flCD19^Cre/+ (KO) mice immunized with PE in CFA or naive controls were analyzed at least 2 months after immunization by flow cytometry for B220⁺PE⁺ cells. (B) Percentage of PE⁺ cells in the various B220⁺Ig⁺ subsets was calculated based on flow cytometric results for both PE-immunized Wt (▪) and KO (□) mice. (C) The percentage of IgM⁺, IgG1⁺, IgG2a⁺, or IgG2b⁺ cells in the B220⁺PE⁺ subset was calculated for both Wt and KO mice. Error bars represent the SEM of at least 2 experiments.