develops from start stage end stage immature B cell CL:0000816 immature B lymphocyte zebrafish_anatomy An immature B cell is a precursor B cell that has the phenotype surface IgM-positive and surface IgD-negative, and have not undergone class immunoglobulin class switching or peripheral encounter with antigen and activation. immature B-lymphocyte immature B-cell ZFA:0009343 newly formed B Cell TAO:0009343 precursor B cell pro-B cell unknown adult