iPCs are transitional in IgG secretion and retain B-cell signatures. (A) IMF of intracellular IgG in sorted p18^+/+ and p18^−/− iPCs and PCs on day 7 after NP-CGG immunization. (B) Proportion of IgG- or IgM-expressing cells by IMF and (C) FACS analysis of cytoplasmic IgG, both in sorted p18^+/+ and p18^−/− populations. (D) Elispot analysis of cells secreting NP-specific IgG (ASC) in unsorted cells (Un) and sorted p18^+/+ and p18^−/− populations after coculturing with MC3T3 cells for 2 days; enzyme-linked immunosorbent assay of relative NP-specific IgG secreted into media. (E) FACS analysis of surface markers in p18^+/+ and p18^−/− populations; gray represents isotype control. (F) qPCR analysis of relative mRNA in sorted p18^+/+ and p18^−/− populations.