NKp44, a triggering receptor involved in tumor cell lysis by activated human natural killer cells, is a novel member of the immunoglobulin superfamily

Surface receptors involved in natural killer (NK) cell triggering during th e process of tumor cell lysis have recently been identified. Of these recep tors, NKp44 is selectively expressed by IL-2-activated NK cells and may con tribute to the increased efficiency of activated. NK cells to mediate tumor cell lysis, Here we describe the molecular cloning of NKp44. Analysis of t he cloned cDNA indicated that NKp44 is a novel transmembrane glycoprotein b elonging to the Immunoglobulin superfamily characterized by a single extrac ellular V-type domain. The charged amino acid lysine in the transmembrane r egion may be involved in the association of NKp44 with the signal transduci ng molecule killer activating receptor-associated polypeptide (KARAP)/DAP12 . These molecules were found to be crucial for the surface expression of NK p44. In agreement with data of NKp44 surface expression, the NKp44 transcri pts were strictly confined to activated NK cells and to a minor subset of T CR-gamma/delta(+) T lymphocytes. Unlike genes coding for other receptors in volved in NK cell triggering or inhibition, the NKp44 gene is on human chro mosome 6.