Mast cells in the inflammatory connective tissue diseases

Objective: To detect mast cells in normal human skin and mast cell infiltration in skin biopsies in patients with systemic sclerosis, systemic lupus erythematosus, Raynaud’s phenomenon, and persons not suffering from any systemic disease. Material and methods: Paraffin histological sections were stained with toluidine blue and by immunoperoxidase method for the von Willebrand factor. Results: In normal human skin mast cells were mostly distributed in the perivascular area of the upper dermis, the perifollicular area and sweat glands. Normal skin mast cell density varied from case to case. In the initial stage, SSc skin showed a significantly increased density of mast cell infiltration as compared with normal controls. Extensive deposition of granules was observed extracellularly around mast cells. There was a wide range of variation in degranulation among the specimens. In advanced stages, SSc was accompanied by flourishing vasculitis and in the most of specimens showed a significant decrease in the density of mast cells. In the late stage of SSc, in areas where extensive deposition of collagen fibers was present and a relatively severe sclerosis was noted, few or no mast cells were present. In SLE patients, the number of mast cells and their degranulation varied depending on the stage of the disease. In patients with Raynaud‘s phenomenon, mast cell infiltration usually did not differ from the patterns found in healthy controls. Expression of vWF factor was found predominantly in endothelial cells and reflected changes in the blood vessel density in different stages of the diseases under study. In edematic tissues, occasionally exravascular leakage of vWF was noted. In the late stage of SSc dominated small blood vessel occlusion, atresia and progressing of fibrosis tissues. No vWF leakage into the perivascular interstitial matrix was detectable in this stage, and the vWF staining was usually restricted to endothelial cells. No vWF leakage was found in healthy skin from control subjects. Conclusion: Skin mast cell density considerably varies among healthy persons. In the early stage of SSc, augmentation of mast cell number and activity of degranulation were found. In the late stages of SSc, the density and activity of degranulation of mast cells decrease. In SLE and Raynaud’s phenomenon patients, generally the population and activity of mast cells varied depending on the stage of disease and were lower than in SSc.