CD27 and infection: During acute infection S+ CD21–CD27+ Bm cells and CD21–CD27– Bm cells represented on average 48.1% and 16.4% of total S+ Bm cells, respectively, and they strongly declined at month 6 (6.3% and 5.3%) and month 12 (3.7% and 6.6%) post-infection (Fig. 2b).