B-1 Cells Carry the Memory of Neonatal Immune Imprinting.

Group A Streptococcus is a common pathogen that elicits a protective humoral response against the cell wall component GlcNAc. In this issue of Immunity, New et al. demonstrate the ability of long-lived B-1 cells to be programmed by microbial colonization and early life immunization to uniquely incorporate GlcNAc reactivity in mice, establishing their critical role in mediating neonatal immune imprinting.