Dual immunostaining for TWEAK and cell lineage markers and cells expressing Fn14. Dual immunostaining for TWEAK (red) and CD68 (blue) in inflamed synovial tissue from a patient with active RA (A). Dual immunostaining for TWEAK (red) with CD38 (blue) with co-expression of TWEAK and CD38 (purple) indicated by arrow (B). C) and D) Dual immunostaining for TWEAK (red) with CD22 (blue). E) TWEAK expression (red) in multinucleated cells (indicated by arrows), and F) by plasma cells in tonsil tissue. Expression of Fn14 (brown) in multinucleated cells (G), and blood vessels of the synovial tissue (H), indicated by arrows. Sections shown in E, F, G, and H were counterstained with haematoxylin. Images shown in B and C were obtained with obj ×10; image shown in A obtained with obj ×20, D, F, G, H with obj ×40 and E with obj ×60.