CD38⁺ GL7⁺ cells directly give rise to memory cells and GC cells. 4 d after injection with PE/CFA, total GL7⁺ cells from CD45.1⁺ animals were FACS purified and adoptively transferred into CD45.2⁺ recipients. (A) Representative flow cytometry plots showing the expression of CD38 and GL7 on PE-specific B cells at the time of adoptive transfer. (B) Representative flow cytometry analysis of CD38 and GL7 expression by the donor CD45.1⁺ PE-specific B cells 2 or 4 d after adoptive transfer into mice injected with PE and CFA or CFA alone at the same time as the donor animals. Data from two individual animals was concatenated for display. (C) Combined data from four experiments showing the total number of PE⁺ donor memory (CD38⁺ GL7⁻), GC (CD38⁻ GL7⁺), and CD38⁺ GL7⁺ cells 2 and 4 d after transfer into uninjected mice or those injected with PE/CFA or CFA alone. The mean and SEM (n = 3–7) are shown.