Influenza-specific IgG memory B-cell response is present among CD27⁻ B cells. B cells were isolated from the PBMCs of 6 HDs and fractionated by CD27 using magnetic bead-based positive and negative selection. The fractions were cultured for 4 days, and IgG-ASCs were measured for each fraction as follows: (A) total, (B) seasonal influenza-specific, and (C) seasonal influenza-specific as a fraction of total. Horizontal bars represent medians.