IST1 structures are present in migratory adhering cell types. (A and B) Immunohistochemistry (IHC) and immunofluorescence (IF) micrographs of temporal artery biopsies of four donors (A) and IHC of appendix and tonsil tissue of one donor (B). IHC sections are labeled for IST1, except for the right image of the second donor of the temporal artery tissue; here an adjacent section was labeled for the fibroblast-marker vimentin. The IF images show the area indicated with a black rectangle in an adjacent section labeled for DAPI (blue), IST1 (magenta), macrophage-marker CD68 (cyan), and vimentin (yellow). The zoomed images show the area indicated with the white rectangle. Arrows indicate IST1-positive cells also positive for CD68 (yellow) or vimentin (orange). As a control for a specific binding of the IST1 antibody, an isotype control staining using a mouse IgG2a antibody was performed. In giant cell arteritis, macrophages infiltrate the adventitia of the vessel wall (black arrows). An inflammatory infiltrate breaking through the internal elastic lamina is labeled with an asterisk. Endothelial cells (e.g., of the vasa vasorum) are positive for IST1, too. The appendix shows the lamina propria (white arrow) in which macrophages and mostly plasma cells are positive for IST1. A lymphatic nodule is indicated with a yellow arrow. In the tonsil, stromal cells are positive for IST1. In the germinal centers (white arrow), plasma cells are positive for IST1 where macrophages are not. This might be explained by the low level of migration of macrophages in the germinal center. In the mantle zones (yellow arrow), macrophages are positive for IST1.