Dendritic cells and IFN-α-producing cells are two functionally distinct non-B, non-monocytic HLA-DR+ cell subsets in human peripheral blood.

At least two distinct HLA-DR⁺ cell subsets lacking surface markers specific for B cells, monocytes or other known lineages are present in human peripheral blood. One subset is non-adherent to plastic, produces interferon-alpha (IFN-α) when incubated with cytomegalovirus-infected target cells and provides an accessory function requited for natural killer (NK) cell-mediated lysis of such cells. These non-adherent HLA-DR⁺ cells express the surface antigen recognized by antibody anti-D44 and do not stimulate mixed leucocyte reaction (MLR). The other HLA-DR⁺ cell subset is loosely adherent to plastic, produces only minimal levels of IFN-α when incubated with cytomegalovirus-infected target cells and does not provide the accessory function required for NK cell-mediated lysis of such cells. These HLA-DR⁺ cells stimulate a strong MLR, do not express D44 antigen and meet the criteria of dendritic cells (DC) morphologically and functionally. [ABSTRACT FROM AUTHOR]