LINEAGE COMMITMENT OF HLA-DR CD38-DEFINED PROGENITOR-CELL SUBPOPULATIONS IN BONE-MARROW AND MOBILIZED PERIPHERAL-BLOOD ASSESSED BY 4-COLOR IMMUNOFLUORESCENCE/

We used four-color fluorescence analysis to compare lineage antigen ex pression in relationship to CD38 and HLA-DR on CD34+ progenitor cells in adult human bone marrow and mobilized peripheral blood. Each of fou r progenitor cell subpopulations defined by HLA-DR and CD38 intensity (CD38-/HLA-DR-, CD38-/HLA-DR+, CD38+/HLA-DR+, and CD38+/HLA-DR-) were present in both progenitor cell sources in similar ratios. The most pr evalent subpopulation consisted of cells that expressed both CD38 and HLA-DR. Virtually ail progenitor cells that lacked CD38 also lacked li neage antigens regardless of their HLA-DR expression. In contrast, the majority of the cells within both CD38+ progenitor cell subpopulation s possessed either lineage antigens or the proliferation-associated an tigen, CD71. Furthermore, CD71 was expressed on three times the number of CD38(+)/HLA-DR- cells when compared with the CD38-/HLA-DR- subpopu lation. Within CD34+ progenitor cell subpopulations defined by the exp ression of CD38 and HLA-DR, the CD38+/HLA-DR- component appears to be the most mature, based on the expression of CD71 and various lineage-a ssociated antigens, including representative markers characterizing ea rly lymphoid, myeloid, and erythroid precursors. Thus, selection of th e most immature CD34+ progenitor cells based solely on the lack of HLA -DR expression results in isolation of two distinct cell populations w ith markedly different maturation status and resultant growth characte ristics.