Morphological and Functional Differences Between HLA-DR+ Peripheral Blood Dendritic Cells and HLA-DR+ FN-Alpha Producing Cells

Abstract

Several cell types, including B cells, NK cells, and monocytes have been proposed to be the cells responsible for IFN-α production in-vitro in response to herpesviruses and other viruses. When Perussia et al¹ described IFN-α producing cells as HLA-DR+ nonadherent, non-monocyte, non-B peripheral blood cells, dendritic cells (DC) became an attractive candidate cells for this function. Subsequently, Bandyopadhyay et al^2,3 showed that the major leukocyte subset in human peripheral blood responsible for IFN-α production upon culture with herpesvirus-infected target cells consists of nonadherent HLA-DR+ cells, which bear no surface markers of B, or T cells, monocytes or NK cells and that these cells also serve as accessory cells for NK cell-mediated lysis of the herpesvirus and HIV-infected targets. Later, Chehimi et al⁴ reported that human peripheral blood mononuclear cells contain at least two distinct HLA-DR+ cell subsets, both of which lack any B and T cell, monocyte and NK cell surface markers. One HLA-DR+ cell subset is plastic nonadherent, produces IFN-α in response to herpesvirus and HIV and provides accessory help to NK cells for lysis of virus-infected targets, but does not induce mixed leukocyte reaction (MLR). The other population has the morphology of dendritic cells (DC), is loosely adherent to plastic, stimulates T cells in the MLR, but neither produces IFN-α when exposed to virus-infected targets nor provides accessory help to NK cells. In this report, we show for the first time morphological, as well as new functional differences, between HLA-DR+ IFN-α producing cells (IPC) and HLA-DR+ DC.