title: In vitro induction of endothelial HLA class II antigen expression by cytomegalovirus-activated CD4+ T cells.
abstract: CMV has been associated with allograft rejection and transplantation-associated arteriosclerosis. CMV infects endothelium, the interface between allograft tissue and the host immune system. Although endothelial HLA class II expression is a hallmark of vascular rejection, CMV does not directly induce these antigens on infected endothelial cells (EC) and, indeed, renders them refractory to HLA DR induction by IFN-gamma. Our earlier studies have demonstrated, however, that CMV-infected EC are capable of eliciting vigorous activation responses by allogeneic, CMV-seropositive donor-derived CD4+ T cells. We now show that T cells thus activated can induce HLA DR expression on noninfected EC. Human umbilical vein endothelial cells (HUVEC) were inoculated at low titer with CMV strain VHL/E, cocultured with allogeneic, CMV-seropositive or CMV-seronegative donor-derived CD4+ T cells, then dual immunohistochemically stained for CMV antigen and HLA DR, or assayed for HLA DR expression by fluorescence flow cytometry. Results demonstrated that HLA DR was induced in 20-70% of HUVEC in monolayers containing less than 0.5% CMV-infected EC after coculture with CMV-seropositive donor-derived T cells. No such induction was observed in experiments employing T cells isolated from CMV-seronegative individuals. Expression of this antigen was strictly limited to noninfected cells. Rare HLA DR induction was observed in virus-free cocultures. To determine whether endothelial HLA DR was induced by a soluble factor(s) elaborated by activated T cells, noninfected HUVEC monolayers were treated for 72 hr with cell-free supernatant from CMV-infected or noninfected HUVEC/T cell cocultures and assayed as above. Again, HLA DR expression was induced by supernatant from CMV-positive cocultures (only when cocultured T cells were isolated from CMV-seropositive donors), but not by supernatant from CMV-negative cocultures or from T cells cultured alone. The soluble factor was identified as IFN-gamma by the complete attenuation of HLA DR induction by anti-IFN-gamma mAb. These findings suggest that allograft endothelium harboring low level CMV may be capable of eliciting host CD4+ T cell activation, and that consequent release of IFN-gamma is capable of inducing endothelial HLA class II expression, as observed in vascular rejection and transplantation-associated arteriosclerosis. Results of these studies thus provide insight into mechanisms that may help elucidate the association between CMV and rejection-related immune events in the allograft.
authors.affiliation: Department of Pathology, Ohio State University College of Medicine, Columbus 43210-1238.
authors.forename: W J
authors.initials: WJ
authors.lastname: Waldman
authors.forename: D A
authors.initials: DA
authors.lastname: Knight
authors.forename: P W
authors.initials: PW
authors.lastname: Adams
authors.forename: C G
authors.initials: CG
authors.lastname: Orosz
authors.forename: D D
authors.initials: DD
authors.lastname: Sedmak
mesh_terms: D000911:Antibodies, Monoclonal; D000956:Antigens, Viral / Q000378:metabolism; D001161:Arteriosclerosis / Q000209:etiology; D001667:Binding, Competitive; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000276:immunology*; D003586:Cytomegalovirus Infections / Q000150:complications / Q000276:immunology; D004730:Endothelium, Vascular / Q000276:immunology* / Q000382:microbiology; D006084:Graft Rejection / Q000209:etiology; D006684:HLA-DR Antigens / Q000096:biosynthesis*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008213:Lymphocyte Activation
chemical_list: D000911:Antibodies, Monoclonal; D000956:Antigens, Viral; D006684:HLA-DR Antigens; D017874:Immediate-Early Proteins; C044582:immediate-early proteins, cytomegalovirus