Enriched Langerhans cells express more HLA-DR determinants than blood-derived adherent cells (monocytes and dendritic cells).

When used as antigen-presenting cells, enriched Langerhans cells (LC) are known to induce a stronger proliferative T-cell response towards antigens than blood-derived adherent cells (a mixture of monocytes and dendritic cells). To study the mechanism behind this difference in accessory cell function, we have compared the quantitative expression of HLA-DR molecules on LC and adherent cells (AdC), using a radioimmunoassay system. The amount of HLA-DR determinants was calculated to be 50-100 times higher on LC than on AdC.