[Effect of CD28 costimulator on T cell receptor(TCR)-induced apoptosis of thymocytes]

To analyze apoptosis and its degree of thymocytes at early and intermediate phases induced by anti-TCRalphabeta mAb or anti-TCRalphabeta mAb+anti-CD28 mAb stimuli, and to analyze the influence of CD28 costimulator on TCR-induced apoptosis of thymocyte subsets.

Thymocytes were freshly prepared and were cultured for 20 h in the presence of anti-TCRalphabeta mAb+anti-CD28 mAb or anti-TCRalphabeta mAb along, The cultured cells were stained with fluorescein labelled Annexin V, PI, anti-CD4 mAb and anti-CD8 mAb, then color reagents. The apoptotic cells were analyzed by FACS.

Compared with the spontaneous apoptosis of thymocytes cultured in medium alone, CD28 costimulator markedly enhanced the number of thymocyte apoptosis at early and intermediate phases; under the action of double signaling stimulators, the apoptosis of CD4(+) CD8(+)(DP) thymocytes were substantially increased, and the expression of CD28 were also upregulated on these apoptotic DP cells.

Influence of CD28 costimulator on TCR-induced apoptosis of thymocyte subsets might be related to thymocyte's mature degree. Double signaling may induce apoptosis of DP thymocytes.