title: Cutting edge: a crucial role for B7-CD28 in transmitting T help from APC to CTL.
abstract: Although APC activation via CD40-CD40L signaling plays a critical role in enabling CD4(+) T cells to provide the "help" necessary for cross-priming of naive CTL, it is unclear how this makes the APC competent for priming. We have investigated the roles of B7-1/B7-2 and their receptors [corrected] CD28/CTLA-4 in cross-priming of CD4-dependent CTL in vivo. We find that both CD28 and B7-1/B7-2 are required for CD40-activated APC to cross-prime CTL, and that priming by CD40-activated APC was prevented by blockade of CD28. Conversely, augmenting CD28 signals with an agonistic Ab bypassed the requirement for CD4(+) T help or CD40 activation. Interestingly, blockade of the negative regulatory B7 receptor CTLA-4 failed to prime CTL in the absence of T help. These results support a model in which activation-induced up-regulation of B7 molecules on APC leads to increased CD28 signaling and a commitment to cross-priming of CD4-dependent CTL.
authors.affiliation: Division of Immune Regulation, La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121, USA.
authors.forename: Kiley R
authors.initials: KR
authors.lastname: Prilliman
authors.forename: Edward E
authors.initials: EE
authors.lastname: Lemmens
authors.forename: Georgia
authors.initials: G
authors.lastname: Palioungas
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Wolfe
authors.forename: James P
authors.initials: JP
authors.lastname: Allison
authors.forename: Arlene H
authors.initials: AH
authors.lastname: Sharpe
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Schoenberger
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology*; D018122:B7-1 Antigen / Q000235:genetics / Q000502:physiology*; D051940:B7-2 Antigen; D018106:CD28 Antigens / Q000502:physiology*; D002460:Cell Line; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018106:CD28 Antigens; C497965:Cd86 protein, mouse; D008562:Membrane Glycoproteins