Immunohistochemical localization of langerhans cells as a tool of vitality in hanging mark wounds

The determination of vitality and wound age is one of the most challenging issues in forensic pathology, about which a large amount of scientific work has been submitted for many decades up until now. In the first minutes or hours, standard histological examination may not distinguish ante mortem wounds from post mortem damages. The immunohistochemical analyses of factors that mediate initial events of the inflammatory reaction are useful to distinguish vital from post-mortem injuries and to reduce the range of vitality estimation. Previous studies have substantially established that cytokines, tryptase and P-selectine are extremely early immunohistochemical markers of vitality in skin injuries. In addition, mast cells and dendritic cells were recently proposed as a tool to discriminate between vital and post mortem lesions. However, the uncertainty in the timing of wounds remains, especially when survival time was short and the standard histological or immunohistochemical examination may not determine whether the wound was inflicted in the pre- or post-mortem period, as well as in hanging death. Hanging death is common and characterized by a very short survival time of the victim and usually macroscopic and histological exams are not able to distinguish vital from post-mortal lesions. The study comprised skin specimens from the edge of vital wounds (with a survival time by 0 to 5 minutes), from ligature marks and from post mortem lesions, compared with control skin specimens taken at 5 or 20 cm from a wound. Cryosections were fixed in cold acetone, stained for hematoxylin eosin, fluorescent avidin, CD1a and MHC class II+ antigens and examined by light microscopy or fluorescence microscopy; digitized photomicrographs were used for image analysis. No differences were found for histological scores, fluorescent avidin, and MHC among controls, vital lesions and ligature marks, suggesting that such markers are stained with a 5 minutes minimum time interval for positivity. Differences were found about Langerhans cells density among vital lesions and ligature marks with the other specimens. The results may be useful in forensic practice when macroscopic and microscopic objective evidence of vitality is absent, and may support the hypothesis that the time of death in hanging is very close (< 5 min) and that, consequently, some of the immunohistochemical markers are not helpful in such cases.