EPIDERMOTROPISM OF T-CELLS CORRELATES WITH INTERCELLULAR-ADHESION MOLECULE (ICAM1) EXPRESSION IN HUMAN PAPILLOMAVIRUS (HPV)-INDUCED LESIONS

Adhesion molecules play an important role in inflammatory reactions. Among them, ICAM1, a ligand for the lymphocyte function-associated antigen (FLA1) of leucocytes, may be expressed by antigen-presenting cells and keratinocytes in various inflammatory disorders. As cell-mediated immune responses play a great role in HPV infections, we investigated the expression of ICAM1 and correlated it with the presence of LFA1-positive cells by immunohistochemistry on serial frozen sections of a series of non-regressing cutaneous and mucosal HPV-induced lesions. ICAM1 expression by keratinocytes was observed only in intensely infiltrated lesions of condylomas and laryngeal papillomas. Its induction was usually correlated with the presence of LFA1-positive cells (mainly CD8-positive cells) which were in close apposition to ICAM1-positive proliferative epithelial cells expressing also, in some cases, HLA-DR antigen. ICAM1 was not correlated with the presence of HPV DNA or viral antigen. In moderately infiltrated lesions, keratinocytes did not express ICAM1, and LFA1-positive cells were not observed in the epidermis. In all lesions, ICAM1 was more intense on endothelial cells than in normal skin; infiltrating cells (lymphocytes and dendritic cells) may also express this antigen but intraepithelial Langerhans cells were devoid of any labelling. These studies provide further evidence that T-lymphocyte mechanisms are important in the host response to HPV-induced lesions. ICAM1 expression correlates with a lesional infiltrate but not with HPV infection and probably results in a more efficient initiation of the immune reaction.