Marginal zone B-cell

Marginal zone B cells are noncirculating mature B cells that segregate anatomically into the marginal zone (MZ) of the spleen.^[1] This region contains multiple subtypes of macrophages, dendritic cells, and the MZ B cells; it is not fully formed until 2 to 3 weeks after birth in rodents and 1 to 2 years in humans.^[2] The MZ B cells within this region typically express high levels of sIgM, CD21, CD1, CD9 with low to negligible levels of sIgD, CD23, CD5, and CD11b that help to distinguish them phenotypically from FO B cells and B1 B cells.

Similar to B1 B cells, MZ B cells can be rapidly recruited into the early adaptive immune responses in a T cell independent manner.^[3] The MZ B cells are especially well positioned as a first line of defense against systemic blood-borne antigens that enter the circulation and become trapped in the spleen.^[4] It is believed they are especially reactive to bacterial cell wall components and self-antigens which are the products of aging.^[3] MZ B cells also display a lower activation threshold than their FO B cell counterparts with heightened propensity for PC differentiation that contributes further to the accelerated primary antibody response.^[5]

In specimens where the tyrosine kinase for Pyk-2 has been knocked-out, marginal zone B-cells will fail to develop while B-1 cells will still be present.^[3]

MZ B-cells are the only B-cells dependent on NOTCH2 signaling for proliferation.^[3]

References

1. ^ Martin F, Kearney JF. Marginal-zone B cells. Nat Rev Immunol. 2002;2(5):323–335.
2. ^ MacLennan IC, Bazin H, Chassoux D, et al. Comparative analysis of the development of B cells in marginal zones and follicles. Adv Exp Med Biol. 1985;186:139–144.
3. ^ ^{a b c d} Hardy, Richard (2008). "Chapter 7: B Lymphocyte Development and Biology". In Paul, William (Book). Fundamental Immunology (6th ed.). Philidelphia, PA: Lippincott Williams & Wilkins. pp. 237–269. ISBN 0-7817-6519-6. 
4. ^ Balazs M, Martin F, Zhou T, et al. Blood dendritic cells interact with splenic marginal zone B cells to initiate T-independent immune responses. Immunity. 2002;17(3):341–352.
5. ^ Lopes-Carvalho T, Foote J, Kearney JF. Marginal zone B cells in lymphocyte activation and regulation. Curr Opin Immunol. 2005; 17(3):244–250