EM Liu, CR Li, XQ Yang, SX Wu

We measured the intracellular calcium concentration, protein kinase A (PKA) activity, and the effect of PMA, which is an activator of protein kinase C, in cord blood mononuclear cells in which apoptosis was induced by stimulation with anti-CD3. We looked at 19 cases of neonatal cord blood and 14 cases of normal adult peripheral blood mononuclear cells (PBMC). In the resting situation, the calcium concentration of the cord blood cells was 88.59 nM and that of PBMC was 107.96 nM. When the cells were stimulated with anti-CD3 for 5 or 10 minutes, the calcium concentration increased in both groups of cells. There were no differences in calcium concentration between cord and peripheral blood cells before or after stimulation. PMA completely corrected apoptosis induced by anti-CD3 in cord blood mononuclear cells. Spontaneous PKA activity in these cells after two hours culture in the absence of mitogen increased from 1.99 to 2.37 (P < 0.01); in PBMC it decreased from 2.15 to 1.83 (P < 0.05). Our results suggest that an imbalance of intracellular signal transduction, especially insufficient PKC activation or translocation to the nucleus, might be the main cause of apoptosis induced by anti-CD3 in cord blood mononuclear cells. But spontaneous apoptosis in cord blood cells may be affected by higher PKA activities in the resting situation.