Characterization of inflammatory cell infiltrate of scleroderma skin: B cells and skin score progression

Background: The purpose of this study was to investigate the frequency and the distribution of inflammatory cell infiltrate in two sets of cutaneous biopsies derived from clinically affected and unaffected skin in patients with systemic sclerosis (SSc) and to test correlation between the cell infiltrate and the progression of skin involvement. Methods: Skin was immunohistochemically assessed to identify CD68, CD3, CD20 and CD138-positive (+) cells in clinically affected and unaffected skin in 28 patients with SSc. Patients were followed for 6 months and the characteristics of the infiltrate were analyzed according to disease duration, clinical features and skin involvement progression. Results: In all SSc cutaneous specimens, cellular infiltrates were found in a perivascular location predominantly in the mid and deeper portions of the dermis. All the analyzed biopsies showed a CD3⁺ and CD68⁺ cell infiltrate and the mean number of CD3⁺ and of CD68⁺ cells was higher in clinically involved skin (CD3⁺, 71.7 ± 34.6 and CD68⁺, 26.3 ± 8.4, respectively) than in clinically uninvolved skin (CD3⁺, 45.7 ± 36.0 and CD68⁺, 13.6 ± 6.1, respectively) (p < 0.001 for both comparisons). CD20⁺ cells were found in 17 (60.7%) patients and in these patients the mean number of CD20⁺ cells was higher in clinically involved (4.7 ± 5.9) than in uninvolved skin (1.9 ± 2.9), (p = 0.04). There was a greater number of CD20⁺ cells in patients with early SSc compared with patients with long-standing disease. CD138⁺ cells were found in 100% of biopsies of clinically involved skin and in 89.3% of biopsies of uninvolved skin. The mean number of CD138⁺ cells was higher in clinically involved skin (3.6 ± 2.3) than in clinically uninvolved skin (1.9 ± 1.7), (p < 0.001). Seven patients experienced more than 20% worsening in the skin score after 6 months of follow up; all of them had a CD20⁺ skin infiltrate on biopsy of clinically involved skin. Conclusions: Our results confirm that mononuclear cells are present in the skin of all patients with SSc, underlining the role of inflammatory cell infiltrates in skin involvement in SSc. B cells in the skin seem to characterize patients with early diffuse skin disease and to correlate with skin progression.