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 involved and uninvolved skin of patients with systemic sclerosis (SSc) and to find correlations between the cell infiltrate and the progression of skin involvement. Methods: Immunohistochemistry was carried out to identify CD68, CD3, CD20 and CD138-positive (+) cells in clinically involved and uninvolved skin of 28 SSc patients. 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 analysed biopsies showed a CD3+ and CD68+ cell infiltrate and the mean number of CD3+, as well as CD68+ cells, was higher in clinically involved skin (CD3+: 71.7±34.6 and CD68+: 26.3±8.4) than in clinically uninvolved skin (CD3+: 45.7±36.0; CD68+: 13.6±6.1), (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 involved (4.7±5.9) than in uninvolved skin (1.9±2.9), (p=0.04). Early SSc had a greater number of CD20+ cells compared with patients with long-standing disease. CD138+ cells were found in 100% of involved skin biopsies and in 89.3% of uninvolved skin samples. 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). Considering the 7 patients that experienced a worsening of skin score higher than 20% after 6-month of follow-up, all of them had presented a CD20+ skin infiltrate in the involved skin biopsy. Conclusions: Our results confirm that mononuclear cells are present in the skin of all SSc patients 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.