NK recognition of cytomegalovirus-infected endothelial cells depends on viral replication and MHC class I expression.
Cytomegalovirus (CMV) infection has been associated with graft rejection in solid organ transplantation and with graft-versus-host disease in marrow transplantation. We hypothesized that CMV-infected endothelial cells play an important role in the rejection process, because of their strategic localization at the interface with the host immune system and their ability to modulate T cell function. To study the effect of CMV infection on cell-mediated cytotoxicity against endothelial cells, peripheral blood mononuclear cells (MNC) were incubated with CMV-infected umbilical vein endothelial cells (CMV-UVEC) or mock-infected controls (M-UVEC) and lysis measured by [3H]leucine release. MNC lysed only CMV-UVEC to a maximum of 23% at E:T 20:1. Lysis was not affected by CD3+ cell depletion, but was abolished by CD16+ cell depletion, indicating that NK cells were the effectors. The kinetics of the NK-mediated lysis of CMV-UVEC paralleled the time course of CMV antigen expression. Furthermore, ganciclovir treatment of CMV-UVEC cultures decreased both specific antigen synthesis and NK-mediated lysis. This indicated that NK might recognize either a viral antigen or a cellular antigen modulated by CMV infection. Treatment of CMV-UVEC with F(ab)2 fragments of human polyclonal anti-CMV antibodies failed to inhibit NK cytotoxicity. In contrast, F(ab)2 fragments of MB40.5, a murine MAb reactive with a conserved epitope on the human MHC class I, significantly decreased lysis, proving that NK lysis of CMV-UVEC is an MHC class I-dependent function. To determine whether CMV-UVEC lysis was dependent solely on upregulation of MHC class I, MNC were incubated with CMV-UVEC mixed with uninfected UVEC. There was no competition for NK-target recognition sites, indicating that NK lysis required an interaction with an MHC class I antigen modified by viral infection. Antibodies against IFN-alpha or -beta did not block NK cytotoxicity against CMV-UVEC. Our findings provide a working frame for further evaluation of cellular immune responses to CMV infection.
Weinberg
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Department of Pediatrics, University of Colorado School of Medicine, Denver 80262, USA.
Zhang
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Tuder
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RM
D000956:Antigens, Viral / Q000276:immunology; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000276:immunology* / Q000502:physiology; D003601:Cytotoxicity Tests, Immunologic; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D015774:Ganciclovir / Q000494:pharmacology; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000276:immunology; D016898:Interferon-alpha / Q000276:immunology; D016899:Interferon-beta / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D014779:Virus Replication
D000956:Antigens, Viral; D015395:Histocompatibility Antigens Class I; D017874:Immediate-Early Proteins; D016898:Interferon-alpha; C044582:immediate-early proteins, cytomegalovirus; D016899:Interferon-beta; D015774:Ganciclovir