Innate-like B-1 cells are developmentally and functionally distinct from B-2 cells. In Immunity, Weiss and colleagues demonstrate a unique role for the receptor-like tyrosine phosphatase CD148 in regulating the B cell antigen receptor (BCR) signaling cascade in B-1 cells. Mice lacking CD148 have defective antibody responses to polysaccharide antigens (T cell independent) commonly found in bacterial capsular coats. CD148-deficient B-1 cells have diminished activation of proximal BCR signaling components. In particular, the Src-family kinase Lyn is activated by CD148 after ligation of the BCR in B-1 cells and positively regulates their production of anti-polysaccharide immunoglobulin M, whereas Lyn negatively inhibits this response in follicular B-2 cells. These findings indicate that the CD148–Lyn axis is required specifically for the antibody responses of B-1 cells and that proximal BCR signaling differs in these two B cell subsets.

Immunity (15 November 2016) http://dx.doi.org/10.1016/j.immuni.2016.10.013