Macrophage subtyping in the determination of age of injection sites.

Determination of the age of injection marks in skin may be of particular interest in the investigation of drug abuse-related fatalities. The aim of our study was to assess the value of macrophage subtyping by antibody-based markers in the determination of the age of injection marks. Immunohistochemical investigations were performed with the antibodies Ki-M1P, 27E10, MRP14, MRP8 and 25F9. Monocytes/macrophages in acute lesions (several hours to 2 days old) expressed proteins detectable with the antibodies 27E10 and MRP14 and showed acute erythrophagia. An additional reaction with the antibody MRP8 was seen in lesions a few days old. An antigen recognized by the antibody 25F9 was found in tissue macrophages, multinucleated giant cells of active granulomas and siderophages. The expression of the 25F9 detectable antigen was absent in inactive granulomas and siderophages, whereas the macrophages were always detectable with the pan-macrophage marker Ki-M1P.