B1-like innate B cells are present in adult human organs in homeostasis.

The study identified B1-like cells in the IgM+ and IgA+ memory compartments across multiple adult human organs. Their transcriptional profile was closer to murine and human prenatal B1 cells than to MZ B cells. B1-like cells expressed markers such as AHNAK and spontaneously secreted IgM; BCR sequencing of paired kidney and spleen samples showed lower clonal diversity and mutation rates in kidney IgM/IgA clones, suggesting spleen-independent seeding.