Umbilical cord blood T lymphocytes are induced to apoptosis after being allo-primed in vitro
In this study, the immunity of umbilical cord blood (UCB) T lymphocytes against allo-antigens was investigated by a standard MLC. No significant difference, between the UCB T cells or peripheral blood (PB) mature T cells, was observed in the primary responses (stimulation index (SI), 51.8 ± 14.8 and 46.5 ± 15.0, respectively). In contrast, in the secondary response, the SI obtained with the CD4 T cells from UCB decreased dramatically (16.3 ± 6.4), while it increased with the CD4 T cells from PB (118.5 ± 21.7), UCB (CD4 and CD8) T cells separately showed much higher frequencies of apoptosis after a primary allo-priming, compared with PB CD4 and CD8 T cells (CD4, UCB 30.5% vs PB 0.8%; CD8, UCB 32% vs PB 1.3%). The higher apoptotic level of the UCB CD4 T cells was confirmed by a second, ELISA-based, Tunel assay (OD values, UCB CD4 1.93 ± 0.31 vs PB CD4 0.59 0.9; P < 0.01). Those apoptotic steps were not attributed to the amount of cytokine (IL-2, 4 and IFN-gamma) production, which was found to be similar in both cases. In conclusion, UCB lymphocytes are much more likely to be induced to apoptosis by allo-priming than adult lymphocytes. This supports their possible, successful engraftment across barriers of HLA incompatibility.
Hagihara, M; Chargui, J; Gansuvd, B; Tsuchida, F; Sato, T; Hotta, T; Kato, S
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