The invention concerns a protein present at the surface of hematopoietic stem cells of the lymphoid cell line and mature NK cells, the corresponding isolated cDNA sequence and their uses as marker of said cells and for preparing antibodies directed against said protein. The invention also concerns the uses of said antibodies for selecting cells expressing at their surface said protein. Said isolated protein has a structure (a) comprising an extracellular domain located between positions 21 and 152, five transmembrane domains located between positions 153 and 295 and a cytoplasmic domain located between positions 296 and 350, with reference to the sequence SEQ ID NO:2; an apparent molecular weight of about 36 to 38 kDa, and its precursor, which comprises in N-terminal of structure (a), a signal sequence of 20 amino acids, is selected in the group consisting of the protein of SEQ ID NO:2, and the proteins having an amino acid sequence having at least 70% identity or at least 85% similarity and preferably at least 95% identity or at least 99% similarity with the sequence SEQ ID NO:2.