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Tomayko MM , Punt JA , Bolcavage JM , Levy SL , Allman DM , Cancro MP
Expression of the Bcl-2 family member A1 is developmentally regulated in T cells
International Immunology. 1999 Nov;11(11) :1753-1761
PMID: ISI:000083797800004   
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During T cell development, cells that fail to meet stringent selection criteria undergo programmed cell death. Thymocyte and peripheral T cell susceptibility to apoptosis is influenced by expression of Bcl-2 family members, some of which are expressed in a developmentally patterned manner. We previously showed developmentally regulated expression of Al, an anti-apoptotic Bcl-2 family member, among B cell developmental subsets. Here we show that cells of the T lineage also express A1 in a developmentally regulated manner. Both A1 mRNA and A1 protein are readily detectable in the thymus, and while present among DN cells, A1 mRNA is up-regulated to very high levels among double-positive (DP) thymocytes. It is then down-regulated to moderate levels among single-positive (SP) thymocytes, and finally expressed at similar to 25-fold lower levels among mature SP CD4(+) and CD8(+) lymph node T cells than among DP thymocytes. Furthermore, we find that in vitro TCR ligation up- regulates A1 expression among both DP and SP thymocytes. Together, these data show that A1 expression is developmentally regulated in T lymphocytes and is responsive to TCR signaling, suggesting that A1 may play a role in maintaining the viability of DP thymocytes.
Times Cited: 3 English Article 257TL INT IMMUNOL