Immunologic dysfunction in scleroderma: evidence for increased mast cell releasability and HLA-DR positivity in the dermis.

To investigate the role of mast cells and cell-mediated immunity in the pathogenesis of scleroderma, we studied wheal size after skin testing with compound 48/80, a liberator of mast cell histamine, and demonstrated increased mast cell releasability in skin that appeared normal, adjacent to involved skin. Immunofluorescent staining for HLA-DR showed dermal positivity in 12 of 13 involved- and 9 of 13 uninvolved-skin biopsy specimens from scleroderma patients, compared with only 1 of 10 controls. By immunoperoxidase staining, most of the DR positivity was found in fibroblast-like cells. These findings further support the notion of immunologic dysfunction in scleroderma.