ResultsThe mean of sPD-1 level was increased (136pg/ml) among dcSSc patients in comparison to healthy controls. Comparison of sPD-1 levels in patients on DMARDs with those without treatment demonstrated significant effect of immunosuppressive therapies, with mean sPD-1 95.1 pg/ml among patients on DMARD compared to 216.7 pg/ml among those on no treatment (p=0.0178). There was association between sPD-1 and mRss (p=0.04) and FVC (p=0.04).
Mean sLAG-3 levels were significantly lower among dcSSc patients (394.6 pg/ml) vs healthy controls (740.8 pg/ml, p=0.0001). sLAG-3 was inversely associated with disease duration (p=0.04). There was a trend for association between sLAG-3 and mRss, with higher levels of sLAG-3 seen in patients with higher skin score (p=0.06),and between sLAG-3 levels and presence of tendon friction rubs (TFR) (mean sLAG-3 366.3 ng/ml among patient without TFR and 531.5 ng/ml among those with TFR, p=0.08). There was highly significant difference in the sTIM-3 levels between healthy controls (mean 4721.9 ng/ml) and dcSSc patients (8728.0 ng/ml, p<0.0001). There was a trend for association between anti-Scl70 (ATA) positivity and sTIM-3 levels (p=0.0944). Hb levels showed significant association with sTIM-3, with higher Hb levels associated with lower sTIM-3 levels (p=0.02).
Pilot flowcytometry studies showed that the proportion of CD4+ T cells expressing PD1 were markedly increased in SSc patients compared to healthy volunteers and Rheumatoid Arthritis patients. There was increased expression of both TIGIT and TIM3 in the CD4+ T cells. (Figure 1 ) Similarly, the co-expression of these receptors on the CD4+ T cell population was elevated compared to healthy volunteers. (figure 2)