Loss of epidermal Langerhans' cells and endothelial cell HLA-DR antigens in the skin in progressive systemic sclerosis.

Skin biopsies from the volar aspect of the forearm were studied in 26 patients with progressive systemic sclerosis (PSS) (16 diffuse, 10 CREST) and 4 controls using monoclonal antibodies against Langerhans' cells, T lymphocytes, macrophages, B lymphocytes, NK/K cells and HLA-DR antigen(s). Langerhans' cells were reduced or absent (anti-T6, anti-HLA-DR) in 19 of 20 clinically involved and in all 6 uninvolved PSS skin biopsies. Electron microscopic studies of 3 PSS patients indicated a reduction in the number of Langerhans' cells, with normal morphology of the remaining. HLA-DR antigen(s) on dermal endothelial cells were absent or reduced in 8 of 20 involved and 5 of 6 uninvolved PSS skin biopsies, but were present on the surface of dermal mononuclear cells presumably representing activated T lymphocytes. Increased numbers of dermal macrophages were found in 19% of PSS biopsies compared with controls. Absence of Langerhans' cells appears to represent the most widespread immunopathological feature of PSS. It is also associated with absent endothelial HLA DR surface antigens and activated T lymphocytes within the dermis.