FUNCTIONAL-ASPECTS OF CORD-BLOOD LYMPHOCYTES RESPONSE TO POLYCLONAL AND ALLOGENEIC ACTIVATION

With the purpose of contributing to a better knowledge of the phenotyp ic characteristics and functional activity of umbilical cord blood (UC B) lymphocytes, we have carried out extensive immunophenotyping of the se cells, evaluated their immune response to polyclonal and allogeneic activation and then compared these results with those obtained with p eripheral blood lymphocytes of healthy donors (PBHD), Our results show ed, in CD4(+) UCB lymphocytes, an increase of CD38 and CD45RA and a de crease of CD11a (S6F1), CD54 and HLA-DR double positive cells. An incr ease of CD38, CD45RA and CD56, and a decrease of CD28, CD57 and HLA-DW were observed in CD8(+) UCB lymphocytes. Most natural killer UCB cell s are CD16(+), CD56(+), CD57(-), and among the UCB cells there is a lo wer number of CD8+ and TCR gamma delta(+) (either CD8(-) or CD8(+)), a nd higher number of CD4(+) lymphocytes, After allogeneic stimulus the majority of these phenotypic differences disappeared, which seems to b e in agreement with the normal allogeneic response (assessed through M LR, frequency of CTL and helper T lymphocytes precursors) presented by UCB lymphocytes, Regarding the response to polyclonal activation, amo ng the mitogens used, only PHA induced a different result: a lower IFN gamma production by UCB cells.