title: CTLA-4 engagement regulates NF-kappaB activation in vivo.
abstract: CTLA-4 engagement inhibits TCR-dependent functions and CTLA-4(-/-) mice develop a lymphoproliferative disorder leading to early lethality. In vitro, ligation of CTLA-4 reduces TCR-mediated activation of NF-kappaB, a transcription factor implicated in promoting T cell survival and cytokine production. However, whether NF-kappaB inhibition downstream of CTLA-4 is necessary for down-regulation of T cell responses is not known. We hypothesized that signaling pathways that are antagonized when CTLA-4 is engaged should be augmented when CTLA-4 is absent and found thatspontaneous NF-kappaB activity was increased in T cells from CTLA-4(-/-) mice. To determine the importance of NF-kappaB inhibition upon CTLA-4 engagement in vivo, CTLA-4(-/-) mice were interbred with mice expressing a transdominant IkappaBalpha mutant under the control of the Lck promoter. The resulting mice had reduced spontaneous NF-kappaB activity in T cells,delayed mortality, and reduced leukocytic accumulation in spleen, lymph nodes, and exocrine pancreas as compared with CTLA-4(-/-) littermates. However, impaired NF-kappaB activation in T cells did not prevent the up-regulation of activation markers on T cells or the acquisition of effector cytokine production. Thus, impaired NF-kappaB activity in T cells prevents specific aspects of the CTLA-4(-/-) phenotype, suggesting that inhibition of NF-kappaB activation is one of the key biochemical events regulated by CTLA-4 ligation in vivo.
authors.affiliation: Department of Medicine, Section of Rheumatology, The University of Chicago, Chicago, Ill 60637 USA.
authors.forename: Helena
authors.initials: H
authors.lastname: Harlin
authors.forename: Kwang Woo
authors.initials: KW
authors.lastname: Hwang
authors.forename: David A
authors.initials: DA
authors.lastname: Palucki
authors.forename: Oliver
authors.initials: O
authors.lastname: Kim
authors.forename: Craig B
authors.initials: CB
authors.lastname: Thompson
authors.forename: Mark
authors.initials: M
authors.lastname: Boothby
authors.forename: Maria-Luisa
authors.initials: ML
authors.lastname: Alegre
mesh_terms: D000069594:Abatacept; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000502:physiology*; D060908:CTLA-4 Antigen; D004268:DNA-Binding Proteins / Q000235:genetics; D020672:I-kappa B Proteins; D018796:Immunoconjugates; D007376:Interleukin-2 / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010179:Pancreas / Q000473:pathology; D013601:T-Lymphocytes / Q000378:metabolism; D019076:Transgenes
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D018796:Immunoconjugates; D007376:Interleukin-2; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D000072000:NF-KappaB Inhibitor alpha; D000069594:Abatacept