Origins and functions of B-1 cells with notes on the role of CD5

Annu Rev Immunol. 2002;20:253-300. doi: 10.1146/annurev.immunol.20.100301.064833. Epub 2001 Oct 4.


Whether B-1a (CD5+) cells are a distinct lineage derived from committed fetal/neonatal precursors or arise from follicular B-2 cells in response to BCR ligation and other, unknown signals remains controversial. Recent evidence indicates that B-1a cells can derive from adult precursors expressing an appropriate specificity when the (self-) antigen is present. Antibody specificity determines whether a B cell expressing immunoglobulin transgenes has a B-2, B-1a or marginal zone (MZ) phenotype. MZ cells share many phenotypic characteristics of B-1 cells and, like them, appear to develop in response to T independent type 2 antigens. Because fetal-derived B cell progenitors fail to express terminal deoxynucleotidyl transferase (TdT) and for other reasons, they are likely to express a repertoire that allows selection into the B-1a population. As it is selected by self-antigen, the B-1 repertoire tends to be autoreactive. This potentially dangerous repertoire is also useful, as B-1 cells are essential for resistance to several pathogens and they play an important role in mucosal immunity. The CD5 molecule can function as a negative regulator of BCR signaling that may help prevent inappropriate activation of autoreactive B-1a cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Autoimmunity
  • B-Lymphocyte Subsets / cytology
  • B-Lymphocyte Subsets / immunology*
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / immunology
  • CD5 Antigens / chemistry
  • CD5 Antigens / genetics
  • CD5 Antigens / metabolism*
  • Cell Differentiation
  • Fetus / cytology
  • Fetus / immunology
  • Humans
  • Immunity, Mucosal
  • Immunoglobulin A / biosynthesis
  • Immunoglobulin M / blood
  • Lymphocyte Activation
  • Mice
  • Phenotype
  • Receptors, Antigen, B-Cell / metabolism
  • Signal Transduction


  • CD5 Antigens
  • Immunoglobulin A
  • Immunoglobulin M
  • Receptors, Antigen, B-Cell