The Plasticity of Newly Formed B Cells

Abstract

Newly formed B cells (NF–B cells) that emerge from the bone marrow to the periphery have often been referred to as immature or transitional B cells. However, NF–B cells have several striking characteristics, including a distinct BCR repertoire, high expression of AID, high sensitivity to PAMPs, and the ability to produce cytokines. A number of findings do not support their designation as immature because NF–B cells have the potential to become Ab-producing cells and to undergo class-switch recombination. In this review, we provide a fresh perspective on NF–B cell functions and describe some of the signals driving their activation. We summarize growing evidence supporting a role for NF–B cells in protection against infections and as a potential source of autoantibody-producing cells in autoimmune diseases such as systemic lupus erythematosus.