IGKV1D-22 and rheumatoid arthritis: S100A8/A9 expression by sublining macrophages, particularly by perivascular macrophages thought to represent newly infiltrated macrophages, is attributable to selective infiltration of S100A8/A9+ monocytes and their endothelium-dependent induction of S100A8/A9 proteins, because the inflamed tissue of RA is characterized by increased vascularity and endothelial cell activation [34].