Vdelta2 T-lymphocyte responses in cord blood samples from Italy and Côte d'Ivoire.

Cord blood T lymphocytes are immature and their functional defect partially reflects a suboptimal level of costimulatory signals provided by neonatal antigen-presenting cells. Neonatal Vdelta2 T lymphocytes, a small component of cellular immunity involved in the response against bacteria, protozoa, virus-infected cells and tumours, are also considered to be immature. Cord blood Vdelta2 T lymphocytes are mostly naïve, proliferate poorly and do not produce cytokines in response to the model phosphoantigen isopentenyl pyrophosphate. We cultured cord blood mononuclear cells with the aminobisphosphonate Pamidronate or with live bacille Calmette-Guérin, and showed that both elicit a strong cord blood Vdelta2 T-cell proliferative response, inducing the expression of activation markers and promoting the differentiation from naïve to memory cells. Our results suggest that cord blood Vdelta2 T cells are not inherently unresponsive and can mount strong responses to aminobisphosphonates and mycobacteria. Neonatal Vdelta2 T lymphocytes may be important participants in responses to microbial infections early in life.