EM Liu, XQ Yang, CR Li, SX Wu

Apoptosis is a main form of physiological cell death. Bcl-2 protein encoded by the protooncogene bcl-2 inhibits apoptosis. In order to clarify temporary dysfunction of the T lymphocytes in neonates, the susceptibility of cord blood mononuclear cells to apoptosis was determined by calculating the percentage of apoptotic cells and analysing DNA fragmentation. In cord blood mononuclear cells, apoptosis was prone to be induced by anti-CD3 as well as spontaneously after 24h of culture, whereas adult peripheral blood mononuclear cells showed a tardive induction of apoptosis only after 72h of culture. The percentage of Bcl-2-positive cells was determined using flow cytometry. The positive rates in cord and adult peripheral blood mononuclear cells were 49.56% and 38.99%, respectively; these were not significantly different (P > 0.05). Apoptosis in cord blood cells could be corrected partly or completely using interleukin 2 (IL-2) but not IL-1 and IFN-γ. These findings suggest that enhanced susceptibility to apoptosis is an important characteristic of T lymphocyte dysfunction in neonates, and that apoptosis in cord blood mononuclear cells may be independent of Bcl-2. It is reasonable to assume that T lymphocytes in neonates might undergo apoptosis to finish the process of post-thymic selection.