title: Role of alpha3 domain of class I MHC molecules in the activation of high- and low-avidity CD8+ CTLs.
abstract: CD8 can serve as a co-receptor or accessory molecule on the surface of CTL. As a co-receptor, CD8 can bind to the alpha3 domain of the same MHC class I molecules as the TCR to facilitate TCR signaling. To evaluate the role of the MHC class I molecule alpha3 domain in the activation of CD8(+) CTL, we have produced a soluble 227 mutant of H-2D(d), with a point mutation in the alpha3 domain (Glu227 --> Lys). 227 mutant class I-peptide complexes were not able to effectively activate H-2D(d)-restricted CD8 T cells in vitro, as measured by IFN-gamma production by an epitope-specific CD8(+) CTL line. However, the 227 mutant class I-peptide complexes in the presence of another MHC class I molecule (H-2K(b)) (that cannot present the peptide) with a normal alpha3 domain can induce the activation of CD8(+) CTL. Therefore, in order to activate CD8(+) CTL, the alpha3 domain of MHC class I does not have to be located on the same molecule with the alpha1 and alpha2 domains of MHC class I. A low-avidity CD8(+) CTL line was significantly less sensitive to stimulation by the 227 mutant class I-peptide complexes in the presence of the H-2K(b) molecule. Thus, low-avidity CTL may not be able to take advantage of the interaction between CD8 and the alpha3 domain of non-presenting class I MHC molecules, perhaps because of a shorter dwell time for the TCR-MHC interaction.
authors.affiliation: Molecular Immunogenetics and Vaccine Research Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. igorbelyakov@yahoo.com
authors.forename: Igor M
authors.initials: IM
authors.lastname: Belyakov
authors.forename: Steven
authors.initials: S
authors.lastname: Kozlowski
authors.forename: Michael
authors.initials: M
authors.lastname: Mage
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Ahlers
authors.forename: Lisa F
authors.initials: LF
authors.lastname: Boyd
authors.forename: David H
authors.initials: DH
authors.lastname: Margulies
authors.forename: Jay A
authors.initials: JA
authors.lastname: Berzofsky
mesh_terms: D000818:Animals; D002460:Cell Line; D006183:H-2 Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D019302:HIV Envelope Protein gp160 / Q000276:immunology; D064532:Histocompatibility Antigen H-2D; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D050505:Mutant Proteins / Q000276:immunology; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D019302:HIV Envelope Protein gp160; D064532:Histocompatibility Antigen H-2D; D050505:Mutant Proteins; D011994:Recombinant Proteins; D007371:Interferon-gamma