Do developing B cells need antigen?

Abstract

Just as potentially useful T cells are positively selected by MHC-peptide complexes in the thymus, it has been proposed that self or commensal bacterial epitopes might select B cell populations with the capacity to recognize polysaccharide or protein structures on pathogens. Recent studies indicate that the repertoire of B cells entering the periphery is not shaped by specific stimuli, but that mature B cell subsets may be under different selective pressures.

Figure 1.

Different modes of BCR signaling are referred to as positive selection. (A) A constitutive tonic signal through the BCR and the Igα–Igβ complex. (B) An authentic antigen binding site–specific signal. (C) A superantigen-like signal that acts through binding of framework residues in the V regions. Examples of B cell subsets in which such type of positive selection takes place are shown.