Functional aspects of cord blood lymphocytes response to polyclonal and allogeneic activation

With the purpose of contributing to a better knowledge of the phenotypic characteristics and functional activity of umbilical cord blood (UCB) lymphocytes, we have carried out extensive immunophenotyping of these cells, evaluated their immune response to polyclonal and allogeneic activation and then compared these results with those obtained with peripheral blood lymphocytes of healthy donors (PBHD). Our results showed, in CD4+ UCB lymphocytes, an increase of CD38 and CD45RA and a decrease of CD11a (S6F1), CD54 and HLA-DR double positive cells. An increase of CD38, CD45RA and CD56, and a decrease of CD28, CD57 and HLA-DR were observed in CD8+ UCB lymphocytes. Most natural killer UCB cells are CD16+, CD56+, CD57-, and among the UCB cells there is a lower number of CD8+ and TCRgammadelta+ (either CD8- or CD8+), and higher number of CD4+ lymphocytes. After allogeneic stimulus the majority of these phenotypic differences disappeared, which seems to be in agreement with the normal allogeneic response (assessed through MLR, frequency of CTL and helper T lymphocytes precursors) presented by UCB lymphocytes. Regarding the response to polyclonal activation, among the mitogens used, only PHA induced a different result: a lower IFNgamma production by UCB cells.