ABSTRACT
<p><b>OBJECTIVE</b>To investigate the possible role and significance of soluble programmed death-1 (sPD-1)/soluble programmed death ligand 1 (sPD-L1) in the pathogenesis of oral lichen planus (OLP).</p><p><b>METHODS</b>Thirty-six patients with OLP (20 cases of reticular OLP and 16 cases of erosive OLP) were enrolled in this study, and 18 healthy people served as controls. Lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD19⁺, CD16⁺ + 56⁺) were examined by flow cytometric analysis and humoral immunity indexes (IgG, IgA, IgM, C3, C4) tested by nephelometry immunoassay. The levels of sPD-1 and sPD-L1 proteins in serum of patients with OLP were determined by enzyme-linked immunosorbent assay. The correlations between the level of sPD-1, sPD-L1 proteins and the immune status and clinical characteristics of patients with OLP were analyzed by SPSS 19.0.</p><p><b>RESULTS</b>CD3⁺, CD4⁺, CD8⁺, CD16⁺ + 56⁺ in patients with OLP were decreased compared with the normal value, while CD19⁺ in patients with OLP was increased compared with the normal value (P < 0.05). C3 and C4 in patients with OLP were decreased compared with the normal value, but IgM in patients with OLP was increased (P < 0.05). The levels of sPD-1 and sPD-L1 proteins in patients with OLP were significantly higher than that in control group [26.10(8.81, 40.00) ng/L vs 17.65(0.00, 26.10) ng/L, 29.53(21.47, 36.76) ng/L vs 22.79(1.19, 28.29) ng/L] (P < 0.05), but the expression of sPD-1 and sPD-L1 was not related with clinical characteristics of OLP. There were negative correlations between the levels of sPD-1 protein and CD4⁺ T cells or CD16⁺ + 56⁺ cells (r1 = -0.378, P1 = 0.007; r2 = -0.365, P2 = 0.009), while there was a positive correlation between the levels of sPD-1 and CD19⁺ B cells (r = 0.482, P = 0.000). There was a negative correlation between sPD-L1 expression level and CD4⁺ and a positive correlation between sPD-L1 expression level and IgG (r¹ = -0.286, P1 = 0.044; r² = 0.365, P₂= 0.029).</p><p><b>CONCLUSIONS</b>In patients with OLP, the cellular immune function is low with humoral immunity function disorder. PD-1/PD-L1 signaling pathway, which might be influenced by the involvement of sPD-1 and sPD-L1 proteins in a certain extent, may play an important role in the immune pathogenesis of OLP.</p>