IMMUNOLOGICAL ANALYSIS OF UMBILICAL-CORD BLOOD-CELLS

Umbilical cord blood can now be considered as an effective source of cells for hematopoietic reconstitution in HLA-identical situations. But it also seems important to evaluate the immune capacity of these cells as they need to have an antileukemic effect when transplanted for acute leukemia. We analyzed 51 umbilical cord blood samples from normal newborns (37-41 weeks old). Phenotypic analysis of cells with monoclonal antibodies and with the use of flow cytometry showed relative values of CD2, CD3, and CD8, identical to normal adult peripheral blood controls (CD2: 78.6+/-10%; CD3: 70+/-13.1%, CD8: 22.1+/-6.1%). We noted higher values of CD4+ cells: 52.7+/-9% (P<0.00001). Among these CD4+ cells 78.6+/-11.2% were of naive phenotype CD45RA+. B-cell levels identified by CD19 and CD20 were lower than in adult blood. The CD38 molecule was expressed on 84.5+/-7% cells but the other activation markers (CD25-DR) were absent. A normal response of mononuclear cord blood cells was observed in mixed lymphocyte culture but these cells showed weak stimulating capacity. No spontaneous NK and LAK activity was observed upon analysis with K562 or Daudi cells. However normal NK or LAK activity was restored after cell incubation with IL2. In conclusion our data confirm the immaturity of cord blood cells, and show their weak stimulating capacity but they also show that their NK and LAK cytotoxicity can be induced.