Ikappa B kinase 2 but not NF-kappa B-inducing kinase is essential for effective DC antigen presentation in the allogeneic mixed lymphocyte reaction.
Although dendritic cells (DCs) are the most potent antigen-presenting cells involved in numerous physiologic and pathologic processes, little is known about the signaling pathways that regulate DC activation and antigen-presenting function. Recently, we demonstrated that nuclear factor (NF)-kappaB activation is central to that process, as overexpression of IkappaBalpha blocks the allogeneic mixed lymphocyte reaction (MLR), an in vitro model of T-cell activation. In this study, we investigated the role of 2 putative NF-kappaB-inducing components, NF-kappaB-inducing kinase (NIK), and IkappaB kinase 2 (IKK2). Using an adenoviral gene transfer method to efficiently express dominant-negative (dn) forms of these molecules in monocyte-derived DCs, we found that IKK2dn but not NIKdn inhibited the allogeneic MLR. When DCs were fixed, this inhibitory effect of IKK2dn was lost, suggesting that IKK2 is involved in T-cell-derived signals that enhance DC antigen presentation during the allogeneic MLR period and does not have an effect on viability or differentiation state of DCs prior to coculture with T cells. One such signal is likely to be CD40 ligand (CD40L), as IKK2dn blocked CD40L but not lipopolysaccharide (LPS)-induced NF-kappaB activation, cytokine production, and up-regulation of costimulatory molecules and HLA-DR in DCs. In summary, our results demonstrate that IKK2 is essential for DC activation induced by CD40L or contact with allogeneic T cells, but not by LPS, whereas NIK is not required for any of these signals. In addition, our results support IKK2 as a potential therapeutic target for the down-regulation of unwanted immune responses that may occur during transplantation or autoimmunity.
Andreakos
Evangelos
E
Kennedy Institute of Rheumatology Division, Faculty of Medicine, Imperial College of Science, Technology and Medicine, London, United Kingdom.
Smith
Clive
C
Monaco
Claudia
C
Brennan
Fionula M
FM
Foxwell
Brian M
BM
Feldmann
Marc
M
D000256:Adenoviridae; D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects*; D023201:CD40 Ligand / Q000494:pharmacology; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase; D007165:Immunosuppression Therapy / Q000379:methods; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013601:T-Lymphocytes; D014161:Transduction, Genetic; D000097782:NF-kappaB-Inducing Kinase
D023201:CD40 Ligand; D051550:I-kappa B Kinase; D008070:Lipopolysaccharides; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D000097782:NF-kappaB-Inducing Kinase; C496559:CHUK protein, human; C496564:Chuk protein, mouse; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse