Contribution of the feline Langerhans cell to the FIV model

In order to identify an equivalent of Langerhans cells in cat stratified epithelia, we used a panel of monoclonal antibodies known to be reactive with membrane antigens present on human Langerhans cells. The labelling was carried out by immunoperoxidase staining, for examination by light microscope, and by immunogold labelling, for electron microscopy. Out of 18 antibodies tested, only one, MHM23 antibody, specific against CD18 antigen, presented reactivity with dendritic epithelial cells on either frozen sections, epidermal sheets or cell suspension cytospins. On the ultrastructural level, these clear, dendritic, CD18+ cells showed "zipper-like" shapes similar to Birbeck granules, which are characteristic ultrastructural markers of Langerhans cells. This observation favours the hypothesis that these CD18+ cells in cat stratified epithelia are the equivalent of human Langerhans cells. These labelled cells were found in all epidermal locations and in the mucous membranes (oral, vaginal, rectal and oesophageal membranes). As feline immunodeficiency virus (FIV) transmission may occur through these membranes, the involvement of these feline Langerhans cells was studied in cats seropositive for FIV.