Quantitative analysis of Fas and bcl-2 expression in hematopoietic precursors

Background and Objectives. We investigated the expression of bcl-2 and CD95 (Apo1-/Fas) on CD34(+) cells obtained from bone marrow (BM), mobilized peripheral blood (MPB), and umbilical cord blood (UCB) samples. The expression of bcl-2 and Fas was then compared with that of other markers usually associated with immaturity; functional tests using the agonistic antibody anti-Fas CH11 were also carried out. Design and Methods. The analysis was performed by flow cytometry on purified CD34(+) cells in a three (CD95 PE, CD34 APC and CD71 FITC) and in a four (CD38 PE, HLA-DR PerCP, CD34 APC and bcl-2 FITC) fluorescence assay. Results, The results were expressed as mean fluorescence index (MFI); bcl-2 expression was significantly higher (p <0.001) in BM (3.73+/-0.63) than in MPB (2.47+/-0.39) and UCB (2.38+/00.58); Fas was significantly less expressed (p <0.001) in UCB (1.27+/-0.78) than in MBP (3.63+/-2.19) and BM (4.56+/-1.69). CD34 expression was significantly (p <0.001) brighter in UCB compared to in MBP and BM, while CD38 and CD71 were significantly (p =0.005 and p <0.001, respectively) more expressed in BM than in MPB and UCB, Fas values were directly correlated to CD38; both Fas and bcl-2 were directly related to CD71 and inversely to CD34, Culture assays showed that hematopoietic precursor cells from BM, WIPE and UCB had a low susceptibility to undergo Fas-mediated apoptosis. Interpretation and Conclusions. In conclusion, bcl-2 and Fas are less expressed in UCB than in MPB and BM; early hematopoietic precursor cells are relatively resistant to CD95-triggered apoptosis; the observed correlation between Fas/bcl-2 and markers of immaturity suggests that they may be determinants of commitment in early hematopoietic precursors. (C) 2001, Ferrata Storti Foundation.