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  • The American Association of Immunologists  (8)
  • 1
    Online Resource
    Online Resource
    IFN-γ Exposes a Cryptic Cytotoxic T Lymphocyte Epitope in HIV-1 Reverse Transcriptase
    The American Association of Immunologists ; 1999
    In:  The Journal of Immunology Vol. 162, No. 12 ( 1999-06-15), p. 7075-7079
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 162, No. 12 ( 1999-06-15), p. 7075-7079
    Abstract: The proteasome, an essential component of the ATP-dependent proteolytic pathway in eukaryotic cells, is responsible for the degradation of most cellular proteins and is believed to be the main source of MHC class I-restricted antigenic peptides for presentation to CTL. Inhibition of the proteasome by lactacystin or various peptide aldehydes can result in defective Ag presentation, and the pivotal role of the proteasome in Ag processing has become generally accepted. However, recent reports have challenged this observation. Here we examine the processing requirements of two HLA A*0201-restricted epitopes from HIV-1 reverse transcriptase and find that they are produced by different degradation pathways. Presentation of the C-terminal ILKEPVHGV epitope is impaired in ME275 melanoma cells by treatment with lactacystin, and is independent of expression of the IFN-γ-inducible proteasome β subunits LMP2 and LMP7. In contrast, both lactacystin treatment and expression of LMP7 induce the presentation of the N-terminal VIYQYMDDL epitope. Consistent with these observations we show that up-regulation of LMP7 by IFN-γ enhances presentation of the VIYQYMDDL epitope. Hence interplay between constitutive and IFN-γ-inducible β-subunits of the proteasome can qualitatively influence Ag presentation. These observations may have relevance to the patterns of immunodominance during the natural course of viral infection.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.162.12.7075
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 1999
    detail.hit.zdb_id: 1475085-5
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    LLT1 and CD161 Expression in Human Germinal Centers Promotes B Cell Activation and CXCR4 Downregulation
    The American Association of Immunologists ; 2016
    In:  The Journal of Immunology Vol. 196, No. 5 ( 2016-03-01), p. 2085-2094
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 196, No. 5 ( 2016-03-01), p. 2085-2094
    Abstract: Germinal centers (GCs) are microanatomical structures critical for the development of high-affinity Abs and B cell memory. They are organized into two zones, light and dark, with coordinated roles, controlled by local signaling. The innate lectin-like transcript 1 (LLT1) is known to be expressed on B cells, but its functional role in the GC reaction has not been explored. In this study, we report high expression of LLT1 on GC-associated B cells, early plasmablasts, and GC-derived lymphomas. LLT1 expression was readily induced via BCR, CD40, and CpG stimulation on B cells. Unexpectedly, we found high expression of the LLT1 ligand, CD161, on follicular dendritic cells. Triggering of LLT1 supported B cell activation, CD83 upregulation, and CXCR4 downregulation. Overall, these data suggest that LLT1–CD161 interactions play a novel and important role in B cell maturation within the GC in humans.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.1502462
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2016
    detail.hit.zdb_id: 1475085-5
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  • 3
    Online Resource
    Online Resource
    Generation of an Immunodominant CTL Epitope Is Affected by Proteasome Subunit Composition and Stability of the Antigenic Protein
    The American Association of Immunologists ; 1999
    In:  The Journal of Immunology Vol. 163, No. 11 ( 1999-12-01), p. 6045-6052
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 163, No. 11 ( 1999-12-01), p. 6045-6052
    Abstract: Generation of the HLA-A0201 (A2) influenza Matrix 58–66 epitope contained within the full-length Matrix protein is impaired in cells lacking the proteasome subunits low molecular protein 2 (LMP2) and LMP7. This Ag presentation block can be relieved by transfecting the wild-type LMP7 cDNA into LMP7-deficient cells. A mutated form of LMP7, lacking the two threonines at the catalytic active site, was equally capable of relieving the block in presentation of the influenza Matrix A2 epitope. These observations were extended by analyzing whether modification of the influenza Matrix protein could overcome the block in presentation of the A2 Matrix epitope. Expression of either a rapidly degraded form of the full-length Matrix protein or shorter Matrix fragments led to an efficient presentation of the A2 influenza Matrix epitope by LMP7-negative cells. These findings demonstrate two main points: 1) LMP7 incorporation into the proteasome is of greater importance for the generation of the influenza A2 Matrix epitope than the presence of the LMP7’s catalytic site; and 2) the interplay between cytosolic proteases and stability of target proteins is of importance in optimization of Ag presentation. These observations may have relevance to the immunodominance of tumor and viral epitopes and raise the possibility that generation of shorter protein fragments could be a mechanism to ensure optimal Ag presentation by cells expressing low levels of LMP7.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.163.11.6045
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 1999
    detail.hit.zdb_id: 1475085-5
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  • 4
    Online Resource
    Online Resource
    Specificity of CTL Interactions with Peptide-MHC Class I Tetrameric Complexes Is Temperature Dependent
    The American Association of Immunologists ; 1999
    In:  The Journal of Immunology Vol. 163, No. 8 ( 1999-10-15), p. 4342-4348
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 163, No. 8 ( 1999-10-15), p. 4342-4348
    Abstract: Tetrameric peptide-MHC class I complexes (“tetramers”) are proving invaluable as reagents for characterizing immune responses involving CTLs. However, because the TCR can exhibit a degree of promiscuity for binding peptide-MHC class I ligands, there is potential for cross-reactivity. Recent reports showing that the TCR/peptide-MHC interaction is dramatically dependent upon temperature led us to investigate the effects of incubation temperature on tetramer staining. We find that tetramers rapidly stain CTLs with high intensity at 37°C. We examine the fine specificity of tetramer staining using a well-characterized set of natural epitope variants. Peptide variants that elicit little or no functional cellular response from CTLs can stain these cells at 4°C but not at 37°C when incorporated into tetramers. These results suggest that some studies reporting tetramer incubations at 4°C could detect cross-reactive populations of CTLs with minimal avidity for the tetramer peptide, especially in the tetramer-low population. For identifying specific CTLs among polyclonal cell populations such as PBLs, incubation with tetramers at 37°C improves the staining intensity of specific CTLs, resulting in improved separation of tetramer-high CD8+ cells. Confocal microscopy reveals that tetramers incubated at 37°C can be rapidly internalized by specific CTLs into vesicles that overlap with the early endocytic compartment. This TCR-specific internalization suggests that coupling of tetramers or analogues with toxins, which are activated only after receptor internalization, may create immunotoxins capable of killing CTLs of single specificities.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.163.8.4342
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 1999
    detail.hit.zdb_id: 1475085-5
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Memory Inflation: Continuous Accumulation of Antiviral CD8+ T Cells Over Time
    The American Association of Immunologists ; 2003
    In:  The Journal of Immunology Vol. 170, No. 4 ( 2003-02-15), p. 2022-2029
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 170, No. 4 ( 2003-02-15), p. 2022-2029
    Abstract: CD8+ T lymphocytes play an important role in the control of intracellular pathogens during both acute and persistent infections. This is particularly true in the case of persistent herpesviruses such as human CMV, which are typified by large virus-specific CD8+ T cell populations during viral latency. To understand the origin of these populations and the factors shaping them over time, we investigated the CD8+ T cell response after murine CMV (MCMV) infection. The kinetics of the acute response were characterized by rapid expansion of activated T cells, followed by a contraction phase. Thereafter, we observed a striking pattern, where MCMV-specific memory CD8+ T cells steadily accumulated over time, with 20% of all CD8+ T cells at 1 year specific for one MCMV epitope. Accumulation of MCMV-specific CD8+ T lymphocytes was seen in all organs tested and was associated with continuous activation of specific CD8+ T lymphocytes, primarily within lymph nodes. The pattern of accumulation was observed in only two of five epitopes tested, and was accompanied by a gradual restriction in usage of the variable region of the TCR β-chain over time. This novel pattern of a virus-specific CD8+ T cell response suggests that continuous or repetitive exposure to Ag can slowly mold memory T cell populations over time. This may be relevant for understanding the evolution of the large human CMV-specific CD8+ T cell populations seen in humans.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.170.4.2022
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2003
    detail.hit.zdb_id: 1475085-5
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  • 6
    Online Resource
    Online Resource
    CD8+ T Cell Epitope-Flanking Mutations Disrupt Proteasomal Processing of HIV-1 Nef
    The American Association of Immunologists ; 2005
    In:  The Journal of Immunology Vol. 175, No. 7 ( 2005-10-01), p. 4618-4626
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 175, No. 7 ( 2005-10-01), p. 4618-4626
    Abstract: CTL play a critical role in the control of HIV and SIV. However, intrinsic genetic instability enables these immunodeficiency viruses to evade detection by CTL through mutation of targeted antigenic sites. These mutations can impair binding of viral epitopes to the presenting MHC class I molecule or disrupt TCR-mediated recognition. In certain regions of the virus, functional constraints are likely to limit the capacity for variation within epitopes. Mutations elsewhere in the protein, however, might still enable immune escape through effects on Ag processing. In this study, we describe the coincident emergence of three mutations in a highly conserved region of Nef during primary HIV-1 infection. These mutations (R69K, A81G, and H87R) flank the HLA B*35-restricted VY8 epitope and persisted to fixation as the early CTL response to this Ag waned. The variant form of Nef showed a reduced capacity to activate VY8-specific CTL, although protein stability and expression levels were unchanged. This effect was associated with altered processing by the proteasome that caused partial destruction of the VY8 epitope. Our data demonstrate that a variant HIV genotype can significantly impair proteasomal epitope processing and substantiate the concept of immune evasion through diminished Ag generation. These observations also indicate that the scale of viral escape may be significantly underestimated if only intraepitope variation is evaluated.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.175.7.4618
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2005
    detail.hit.zdb_id: 1475085-5
    Location Call Number Limitation Availability
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  • 7
    Online Resource
    Online Resource
    Memory Inflation: Continous Accumulation of Antiviral CD8+ T Cells Over Time
    The American Association of Immunologists ; 2003
    In:  The Journal of Immunology Vol. 171, No. 7 ( 2003-10-01), p. 3895-3895
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 171, No. 7 ( 2003-10-01), p. 3895-3895
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.171.7.3895-b
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2003
    detail.hit.zdb_id: 1475085-5
    Location Call Number Limitation Availability
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  • 8
    Online Resource
    Online Resource
    Ultrasensitive Detection and Phenotyping of CD4+ T Cells with Optimized HLA Class II Tetramer Staining
    The American Association of Immunologists ; 2005
    In:  The Journal of Immunology Vol. 175, No. 10 ( 2005-11-15), p. 6334-6343
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 175, No. 10 ( 2005-11-15), p. 6334-6343
    Abstract: HLA class I tetramers have revolutionized the study of Ag-specific CD8+ T cell responses. Technical problems and the rarity of Ag-specific CD4+ Th cells have not allowed the potential of HLA class II tetramers to be fully realized. Here, we optimize HLA class II tetramer staining methods through the use of a comprehensive panel of HIV-, influenza-, CMV-, and tetanus toxoid-specific tetramers. We find rapid and efficient staining of DR1- and DR4-restricted CD4+ cell lines and clones and show that TCR internalization is not a requirement for immunological staining. We combine tetramer staining with magnetic bead enrichment to detect rare Ag-specific CD4+ T cells with frequencies as low as 1 in 250,000 (0.0004% of CD4+ cells) in human PBLs analyzed directly ex vivo. This ultrasensitive detection allowed phenotypic analysis of rare CD4+ T lymphocytes that had experienced diverse exposure to Ag during the course of viral infections. These cells would not be detectable with normal flow-cytometric techniques.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.175.10.6334
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2005
    detail.hit.zdb_id: 1475085-5
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