IL17A and oral lichen planus: Although no correlation between IL-23p19 staining scores and IL-17+ cell numbers was found in the total OLP group or erosive OLP subgroup, there were positive correlations between the expressions of IL-23 and IL-17 at both protein and mRNA levels in reticular OLP subgroup, indicating that the upregulation of IL-23 is associated with increased levels of IL-17 in the early stage of OLP lesion.