Quantification of IL-17 Expression in PsA

Quantification of IL-17A-, IL-17F-, IL17RA- and IL-17RC-expressing cells in PsA skin and synovial tissues was performed by computer-assisted image analysis, as previously described [29 (link)]. Briefly, after immunohistochemical staining, all coded sections (one section per patient per time-point) were randomly analyzed (18 high-power fields from different parts of the section were analyzed; the mean of the 18 high-power fields was calculated). The images of the high-power fields were analyzed using the Qwin analysis system (Leica, Cambridge, UK). The expression of stained proteins was calculated for each section as the median integrated optical density (IOD)/mm² [33 (link)].