Biology:Transitional B cell
Transitional B cells are B cells at an intermediate stage in their development between bone marrow immature cells and mature B cells in the spleen. Primary B cell development takes place in the bone marrow, where immature B cells must generate a functional B cell receptor (BCR) and overcome negative selection induced by reactivity with autoantigens.[1] Transitional cells can be found in the bone marrow, peripheral blood, and spleen, and only a fraction of the immature B cells that survive after the transitional stage become mature B cells in secondary lymphoid organs such as the spleen.
Characteristic of transitional cells
The term "transitional B cell" was first used in 1995 for cells that are developmentally intermediate between immature bone marrow B lineage cells and fully mature naïve B cells in the peripheral blood and secondary lymphoid tissues, found in mice. In humans, it is postulated that the transitional cells, after leaving the bone marrow, are subjected to peripheral checks to prevent the production of autoantibodies.[2] Transitional B cells that survive selection against autoreactivity develop eventually into naive B cells.[3] Given the fact that only a small fraction of immature B cells survive the transition to the mature naive stage, the transitional B cell compartment is widely believed to represent a key negative selection checkpoint for autoreactive B cells.[4][5] All transitional B cells are high in heat-stable antigen (HSA, CD24) relative to their mature counterparts and express the phenotypic surface markers AA4.[6]
T1 and T2
There are two transitional stages for the B cells in mouse, T1 and T2, with the T1 stage occurring from its migration from the bone marrow to its entry into the spleen, and the T2 stage occurring within the spleen where they developed into mature B cells.[7] As in the mouse, human transitional cells can be found in the bone marrow, peripheral blood, and spleen. However, in contrast to the nuanced models proposed in the mouse, thus far human studies have, by and large, described a rather homogeneous population of transitional B cells (T1/T2) defined by the expression of high levels of CD24, CD38 and CD10.[1][8]
Overall there is general agreement on the markers used to separate the subpopulations, although some differences exist in the number of subgroups and in the functional characteristics of the T2 population. T1 B cells are distinguished from the other subsets by the following surface marker characteristics: they are IgMhiIgD−CD21−CD23−, whereas T2 B cells retain high levels of surface IgM but are also IgD+CD21+ and CD23+.[8] Differences in functional characteristics of the T2 subpopulation reported by different laboratories are unexplained, although they might be due to differences in isolation strategies. In any case, there is consensus that T2 B cells clearly differ functionally from T1 B cells.[9]
See also
References
- ↑ 1.0 1.1 "Identification and characterization of circulating human transitional B cells". Blood 105 (11): 4390–8. 1 June 2005. doi:10.1182/blood-2004-11-4284. PMID 15701725.
- ↑ "Predominant autoantibody production by early human B cell precursors". Science 301 (5638): 1374–1377. 2003. doi:10.1126/science.1086907. PMID 12920303. Bibcode: 2003Sci...301.1374W.
- ↑ "Differential expression of CD21 identifies developmentally and functionally distinct subsets of human transitional B cells". Blood 115 (3): 519–529. 2010. doi:10.1182/blood-2009-07-234799. PMID 19965666.
- ↑ "Transitional B cells are the target of negative selection in the B cell compartment". J Exp Med 181 (6): 2129–40. 1 June 1995. doi:10.1084/jem.181.6.2129. PMID 7760002.
- ↑ "B cell development in the spleen takes place in discrete steps and is determined by the quality of B cell receptor-derived signals". J Exp Med 190 (1): 75–89. 5 July 1999. doi:10.1084/jem.190.1.75. PMID 10429672.
- ↑ "Commitment to the B lymphoid lineage occurs before DH–JH recombination". J. Exp. Med. 189 (4): 735–740. 1999. doi:10.1084/jem.189.4.735. PMID 9989989.
- ↑ James B. Petro; Rachel M. Gerstein; John Lowe; Robert S. Carter; Nicholas Shinners; Wasif N. Khan (December 2002). "Transitional Type 1 and 2 B Lymphocyte Subsets Are Differentially Responsive to Antigen Receptor Signaling". J. Biol. Chem. 277 (50): 48009–19. doi:10.1074/jbc.M200305200. PMID 12356763. http://www.jbc.org/content/277/50/48009.full.
- ↑ 8.0 8.1 "Expansion of functionally immature transitional B cells is associated with human-immunodeficient states characterized by impaired humoral immunity". J. Immunol. 176 (3): 1506–16. 1 February 2006. doi:10.4049/jimmunol.176.3.1506. PMID 16424179. http://www.jimmunol.org/content/176/3/1506.long.
- ↑ "CD23 defines two distinct subsets of immature B cells which differ in their responses to T cell help signals". Int. Immunol. 14 (2): 157–166. 2002. doi:10.1093/intimm/14.2.157. PMID 11809735.
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