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I Interaction (i + interaction)

Distribution by Scientific Domains

Medical Sciences	50%
Chemistry	50%

Selected Abstracts

Requirement for Q226, but not multiple charged residues, in the class I MHC CD loop/D strand for TCR-activated CD8 accessory function

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2003
Micheal Durairaj
Abstract Activation of CD8+ cytotoxic T lymphocytes typically begins with recognition of class I MHC-peptide complexes by the TCR and CD8 as a coreceptor. In its coreceptor role, CD8 binds thesame class I-peptide antigen complex as the TCR, enhancing the strength of TCR-class I interaction. Subsequent to initial TCR engagement, CD8 acts as an accessory molecule by binding any properly conformed class I molecules on the target cell surface, leading to CD8-mediated adhesion and cosignaling functions. We expressed and isolated a number of mutant class I molecules in which one or moreacidic or polar residues in the class I ,3 domain CD loop and D strand region, or ,2 domain were altered. Using solid phase CTL adhesion and degranulation assays with isolated class I molecules, we demonstrate that multiple acidic residues in the ,3 domain, although involved in CD8 coreceptor interaction, are not required for TCR-activated CD8 accessory interactions. Instead, we show that Q226, a polar group on the end of the CD loop, is required for TCR-activated CD8 accessory functions. These results indicate that CD8 coreceptor and accessory interactions differ substantially and suggest that TCR activation results in changes that alter the structural constraints for CD8 accessory interactions. [source]

Tetramer-blocking assay for defining antigen-specific cytotoxic T lymphocytes using peptide-MHC tetramer

CANCER SCIENCE, Issue 2 2006
Hiroshi Yokouchi
Peptide-MHC tetramers have been engineered to allow accurate detection of antigen-specific cytotoxic C lymphocytes (CTL) by flow cytometry. Here, we propose a novel use for peptide-MHC tetramers in the specific and sensitive analysis of the cytotoxic function of antigen-specific CTL by blocking MHC-restricted antigen-specific cytotoxicity. We found that pretreatment of ovalbumin (OVA)-specific CD8+ CTL (OT-1 CTL), derived from OT-1 T-cell receptor (TCR)-transgenic mice, with OVA257,264 peptide-H-2Kb tetramer caused a marked inhibition of the cytotoxicity against OVA-expressing EG-7 tumor cells. OVA257,264 peptide-H-2Kb tetramer did not block the cytotoxicity mediated by 2C mouse (H-2b)-derived CD8+ CTL, which recognize allo (H-2Ld) antigens. Moreover, OT-I CTL activity was not inhibited by an irrelevant HBV208,216 peptide-H-2Kb tetramer. These results indicate that the blocking of CTL activity with peptide-MHC tetramer was caused by interference with the interaction between the TCR and H-2Kb -OVA257,264 peptide complex, but not with the CD8-MHC class I interaction. The blocking activity of OVA257,264 peptide-H-2Kb tetramer was reversible because OT-I CTL pretreated with the tetramer recovered their cytotoxicity after culturing with interleukin-2 for 24 h. The same results were also demonstrated in freshly isolated, in vivo -primed OT-1 CTL sorted by the tetramer. These results demonstrate that peptide-MHC tetramer is a useful tool for defining MHC-restricted antigen-specific CTL function. Moreover, our finding implies that the measurement of CTL activity immediately after tetramer-guided sorting is not a suitable method for evaluating the function of in vivo -induced tetramer-positive CTL. We believe that the tetramer-blocking assay presented here will be useful for functionally monitor the induction of MHC-restricted antigen-specific CTL during vaccination therapy against tumor and infectious diseases. (Cancer Sci 2006; 97: 148 ,154) [source]

Reaction of tellurium tetraiodide with 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene,

HETEROATOM CHEMISTRY, Issue 5 2005
Norbert Kuhn
2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene 1 (Carb, R1 = iPr, R2 = Me) reacts with TeI4 to give the carbene adduct CarbTeI2 (3). The crystal structure of 3 consists of T-shaped monomeric fragments linked by weak Te. I interactions to form infinite helical chains. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:316,319, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20090 [source]

Trimethyl[3-methyl-1-(o -tolenesulfonyl)indol-2-ylmethyl]ammonium iodide and benzyl[3-bromo-1-(phenylsulfonyl)indol-2-ylmethyl]tolylamine

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2002
P. R. Seshadri
The title compounds, C20H25N2O2S+·I,, (I), and C29H25BrN2O2S, (II), respectively, both crystallize in space group P. The pyrrole ring subtends an angle with the sulfonyl group of 33.6° in (I) and 21.5° in (II). The phenyl ring of the sulfonyl substituent makes a dihedral angle with the best plane of the indole moiety of 81.6° in (I) and 67.2° in (II). The lengthening or shortening of the C,N bond distances in both compounds is due to the electron-withdrawing character of the phenylsulfonyl group. The S atoms are in distorted tetrahedral configurations. The molecular structures are stabilized by C,H,O and C,H,I interactions in (I), and by C,H,O and C,H,N interactions in (II). [source]