Elevated serum L-selectin levels and decreased L-selectin expression on CD8(+) lymphocytes in systemic sclerosis

Abstract

L-selectin is expressed on most circulating leucocytes and mediates leucocyte rolling on endothelium at sites of inflammation. Following rolling or activation of leucocytes, cell surface L-selectin is released as soluble L-selectin (sL-selectin). In the present study, we assessed serum levels of sL-selectin by ELISA and blood leucocyte L-selectin expression by flow cytometry in patients with systemic sclerosis (SSc). Serum levels of sL-selectin in patients with SSc (n = 51) were significantly higher than in normal controls (n = 30) while sL-selectin levels were similar for systemic lupus erythematosus patients (n = 20) and normal controls. Furthermore, SSc patients with elevated sL-selectin levels had inflammatory joint involvement, pitting scar/ulcers, and diffuse pigmentation more frequently than those with normal sL-selectin levels. The frequency of L-selectin(+) population among CD8(+) T cells was significantly decreased in SSc patients (n = 30) compared with normal controls (n = 20), while that among CD4(+) T cells, B cells, monocytes, and neutrophils was similar for SSc patients and normal controls. These suggest that elevated sL-selectin levels and decreased frequency of L-selectin+ CD8(+) T cells in SSc patients may be involved in inflammation associated with SSc.

Figures

Fig. 1

Serum levels of sL-selectin in patients with SSc and controls (CTL). sL-selectin levels were determined by ELISA. N.S. = not significantly different.

Fig. 2

Flow cytometry analysis on peripheral blood lymphocytes from patients with SSc and normal controls. Expression of CD8 by L-selectin+ (a) and expression of CD4 by L-selectin+ (b). All samples were stained in parallel and analysed sequentially by flow cytometry with identical instrumental settings. These results are representative of those obtained with 30 patients with SSc and 23 normal controls.

Fig. 3

The frequencies of L-selectin+ leucocyte subpopulations from patients with SSc. a, CD4+ T cell; b, CD8+ T cell; c, CD16+NK cell; d, CD14+ monocyte. The frequencies of L-selectin+ lymphocytes were determined by two-colour immunofluorescence staining with flow cytometric analysis. All samples were stained and analysed sequentially by flow cytometry in parallel using identical instrument settings.

Fig. 4

The frequencies of HLA-DR-expressing CD8+ T cell subpopulations from patients with SSc. The frequencies of HLA-DR+ lymphocytes were determined by two-colour immunofluorescence staining with flow cytometric analysis. All samples were stained and analysed sequentially by flow cytometry in parallel using identical instrument settings.