Immunoelectron Microscopic Investigation of HLA-DR-Positive Dendritic Cells at the Dermo-Epidermal Junction in Skin Disorders Associated with the Deposition of Immune Complexes

HLA-DR-positive dendritic cells present at the dermo-epidermal junction in skin disorders associated with the deposition of immunoglobulins and/or complement factors in the skin biopsy are investigated ultrastructurally. They demonstrate long, slender cytoplasmic processes, an indented nucleus, and strikingly dilated cisternae of the endoplasmic reticulum. HLA-DR antigen is present on the plasma membrane and within some of the dilated cisternae. These findings further support our previously formulated hypothesis that these cells represent a functionally active stage of antigen-presenting cells.