NK CELLS DIFFERENTIATED FROM BONE-MARROW, CORD-BLOOD AND PERIPHERAL-BLOOD STEM-CELLS EXHIBIT SIMILAR PHENOTYPE AND FUNCTIONS

In the present study, we investigated the differentiation of human NK cells from bone marrow, cord blood and mobilized peripheral blood puri fied CD34(+) stem cells using a potent culture system. Elutriated CD34 (+) stem cells were grown for several weeks in medium supplemented wit h stem cell factor (SCF) and IL-15 in the presence or absence of a mur ine stromal cell line (MS-5). Our data indicate that IL-15 induced the proliferation and maturation of highly positive CD56(+) NK cells in b oth types of culture, although murine stromal cells slightly increased the proliferation of NK cells. NK cells differentiated in the presenc e of MS-5 were mostly CD56(+) CD7(-) and a small subset expressed CD16 . These in vitro differentiated CD56(+) NK cells displayed cytolytic a ctivity against the HLA class I- target K562. The CD56(+) CD16(+) subs et also lysed NK-resistant Daudi cells. Neither of these NK subsets we re shown to express Fas ligand. Total CD56(+) cells expressed high amo unts of transforming growth factor-beta and granulocyte-macrophage col ony-stimulating factor, but no IFN-gamma. Investigation of NK receptor expression showed that most CD56(+) cells expressed membrane CD94 and NKG2-A mRNA. PCR analysis revealed that p58 was also expressed in the se cells. The role of CD94 in NK cell-mediated cytotoxicity was assess ed on human HLA-B7-transfected murine L cells. While a low cytotoxic a ctivity towards HLA-B7 cells was observed, the HLA-DR4 control cells w ere killed with high efficiency. These studies demonstrate that cytoly tic and cytokine-producing NK cells may be derived from adult and feta l precursors by IL-15 and that these cells express a CD94 receptor whi ch may influence their lytic potential.