The generation of human dendritic and NK cells from hemopoietic progenitors induced by interleukin-15

Interleukin-15 (IL-15) is a pleiotropic cytokine that induces the generatio n and differentiation of lymphoid cells and shares many biological activiti es with IL-2, We have shown here the development of dendritic cells (DC) fi om human CD34(+) hemopoietic precursor cells cultured for 2-4 weeks with I L-15 alone. DC generated with IL-15 have typical morphological, immunocytoc hemical, phenotypic, and functional characteristics of mature DC, Dual flow cytometry analysis performed weekly demonstrated increasing co-expression of CD1a or CD83 with HLA-DR, CD80, CD86, IL-2R alpha, beta, and gamma, Two populations of cells were distinguished among CD34(+) progeny. Small and me dium-size cells were mainly natural killer (NK) cells (72.6-85.2% CD56(+)) and low numbers of DC (9.1-21.3% CD1a(+)). Large cells were mostly DC (75.4 -95.4% CD1a(+)), Isolated CD34(+) cells did not express IL-2R subunits but after 2-3 days in culture with IL-15, they were found to express IL-2R gamm a, Induced expression of IL-2R gamma on CD34(+) cells may explain the prima ry mechanism of IL-15-regulated differentiation of hemopoietic precursor ce lls. Thus, our data suggest that IL-15 stimulates CD34(+) cells to differen tiate into NIC and DC and may represent a new growth and survival factor fo r lymphoid DC.