Abstract
An important factor in shaping the T-cell receptor (TcR) repertoire during thymocyte development is the susceptibility of double-positive (CD4+ CD8+) thymocytes to induction of apoptosis (negative selection) when the TcR is engaged by 'self-antigens. Recent evidence has suggested that this susceptibility to apoptosis may be influenced by the expression of bcl-2, a proto-oncogene known to increase the resistance to apoptosis in various cell systems. Using a semi-quantitative polymerase chain reaction (PCR) technique in conjunction with staged embryonic material and purified thymocyte subpopulations we have investigated patterns of bcl-2 expression during normal T-cell development. Our results show that while bcl-2α gene expression is readily detectable in immature CD3- CD4- CD8- thymocytes and in mature single-positive TcR(hi) cells, it is drastically reduced in TcR negative double-positive (CD3- CD4- CD8+) cortical thymocytes of intermediate maturity. Careful mapping of bcl-2α re-expression in relation to the onset of TcR expression within the population of embryonic thymocytes indicates that bcl-2α is up-regulated as soon as TcR molecules are expressed on the surface of CD4+ CD8+ thymocytes. Therefore, thymocytes susceptible to apoptosis on TcR ligation express bcl-2α mRNA suggesting that changing levels of bcl-2 expression are unlikely to be the only determinant regulating susceptibility to apoptosis in the thymus. The possible implications of these changes in bcl-2 expression regarding other facets of thymocyte development will be discussed.
Original language | English |
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Pages (from-to) | 115-119 |
Number of pages | 5 |
Journal | Immunology |
Volume | 81 |
Issue number | 1 |
Publication status | Published - 1994 |
ASJC Scopus subject areas
- Immunology and Allergy
- Immunology