The Allograft Inflammatory Factor-1 (AIF-1) homologous in Hirudo medicinalis (medicinal leech) is involved in immune response during wound healing and graft rejection processes

Allograft inflammatory factor-1 (AIF-1) is a 17 kDa cytokine-inducible calcium-binding protein that in Vertebrates plays an important role in allografts immune response. Since its expression is mainly limited to the monocyte/macrophage lineage, it was recently suggested that it could play a key role during inflammatory responses, allograft rejection, as well as in the activation of macrophages. To clarify this point we have focused our research on the possible role of AIF-1 during the inflammatory response after injury in the leech Hirudo medicinalis (Annelida, Hirudinea). This invertebrate is an excellent animal model since the responses evoked during inflammation and tissue repair are clear and easily detectable and have a striking similarity with vertebrate responses. Moreover the analysis of an EST library from H. medicinalis CNS, revealed the presence of a gene, named Hmaif-1/alias Hmiba1, showing a high homology with vertebrate aif-1. Our data show that the related protein, named HmAIF-1, is constitutively expressed in unlesioned leeches and that dramatically increases 48 h after wounds and tissue transplants. Immunohistochemistry experiments, using a specific anti HmAIF-1 polyclonal antibody, shows that this factor is present in spread, CD68+ /CD45+ macrophage-like cells. A few days after experimental wounding of the body wall, the amount of these immunopositive cells increases at the lesion site. In conclusion here we propose that in leech HmAIF-1 factor is involved in inflammation events like its vertebrate counterparts.