Over the past several decades, significant progress has been made in understanding the roles of B cells in immunity and autoimmunity. B-cell development, occurring in the bone marrow, is a complex dynamic process involved in immunoglobulin (Ig) gene rearrangement and B-cell receptor (BCR) expression. Early progenitor B (pro-B) cells initiate DNA rearrangement at their Ig heavy chain loci, resulting in the synthesis of m-chains in the cytoplasm and the assembly of the precursor B-cell receptor (pre-BCR). Following the successful rearrangement of light chain genes, these precursor B (pre-B) cells differentiate into immature B cells when whole IgM molecules are expressed as functional BCR on the cell surface. The newly formed immature B cells then leave the bone marrow and become mature B lymphocytes in the peripheral lymphoid organs.
