To quantify the expression of CD44 and variant isoforms CD44v3 and CD44v6 on T cells from patients with systemic lupus erythematosus (SLE), and to assess correlations of the level of expression of these molecules with disease manifestations.

Information on clinical and demographic characteristics was collected, and blood samples were obtained from 72 patients with SLE and 32 healthy control subjects matched to the patients by sex, race, and age. Expression of CD44 and variants CD44v3 and v6 on T cell subsets was determined by flow cytometry, and Pearson's correlations of their expression levels with clinical variables, SLE Disease Activity Index (SLEDAI) scores, and presence of lupus nephritis were determined. Wilcoxon's rank sum tests and conditional multivariable regression analyses were applied to identify differences in the expression of CD44 between patients with SLE and healthy controls.

Expression of CD44 was higher on CD4+ and CD8+ T cells from SLE patients compared with controls (P ≤ 0.03). Expression of CD44v3 and CD44v6 was also higher on total T cells and CD4+ and CD8+ T cells from SLE patients compared with controls (P ≤ 0.03). Cell surface levels of CD44v3 on total T cells, CD4+ T cells, and CD8+ T cells as well as cell surface expression of CD44v6 on total T cells and CD4+ T cells were correlated with the SLEDAI score (P < 0.05). The presence of lupus nephritis was associated with the expression of CD44v6 on total T cells, CD4+ T cells, and CD4−CD8− T cells (P < 0.05). Positivity for anti–double‐stranded DNA antibodies was associated with the expression levels of CD44v6 on T cells (P < 0.05).

These results indicate that expression levels of CD44v3 and CD44v6 on T cells may represent useful biomarkers of SLE activity.