Role of HLA-G versus HLA-E on NK function: HLA-G is able to inhibit NK cytolysis by itself

Recent studies have shown that endogenous HLA-E molecules are stabilized on the cell surface upon the expression of HLA-G which contains within its le ader sequence, a nonapeptide capable of binding with the HLA-E/beta 2m comp lex. Since HLA-E was found to be the major ligand for the CD94/NKG2A inhibi tory receptor, we determined the role of HLA-G versus HLA-E on NK lysis inh ibition. We showed that K562 cells transfected with HLA-G1 cDNA are protect ed from NK lysis by direct interaction between HLA-GI and killing inhibitor y receptor(s). This NK lysis inhibition is not dependent on HLA-E expressio n, since no HLA-E protein was detected on K562 cells; HLA-G1 is therefore a ble to inhibit NK lysis by itself. (C) 1999 Elsevier Science Ireland Ltd. A ll rights reserved.