IHC staining and classical HSMI changes. Immunostaining with μ1c-antibodies of heart section from the cohabitant group 12 wpi. Characteristic histopathological changes of HSMI with epicarditis (arrow) and a major inflammatory response in the outer part of the compact layer. No positive immunostained cells observed within the inflammatory reaction. PRV antigen is detected outside the area of inflammation (arrowhead) in the inner part of the compactum, as well as in the spongy layer (lower left corner). Negative control presented in the top left corner.