Circulating HLA-DR+ natural killer cells have potent lytic ability and weak antigen-presenting cell function

Whether a freshly isolated immune cell can be equipped with both natural killing and antigen-presenting cell (APC) function has recently become controversial in mice. We sought to probe the existence of a candidate human cell with these properties by searching for cells in healthy subjects that co-express APC surface molecules and NK cell receptors. We have found that CD3(-)CD14(-)CD19(-) mononuclear cells of human blood, spleen, liver, and lymph nodes contain two distinct populations of cells that co-express HLA-DR (DR) and CD56. Circulating CD56(+) cells expressing high levels of DR were phenotypically and functionally similar to conventional CD56-dendritic cells (DC). Furthermore, we demonstrate here that a separate cohort of CD56(+) cells that express low levels of DR are NK cells that possess dual function as potent killers endowed with weak APC function. (C) 2008 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.