IL-4 enhances sIgM expression in B cells from healthy human donors. (A) Depicts the gating strategy for determining the naive and memory B cells from normal donors and described in detail in the supplemental methods. (B) PBMCs were extracted and treated with and without IL-4 (10 ng/mL) for 24 hours. Using the gating strategy in (A), sIgM levels were quantitated by flow cytometry in the naive and memory B cell. Statistical significance was determined by a paired Student t test where indicated (B).