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1.
J Immunol ; 167(10): 5620-7, 2001 Nov 15.
Article in English | MEDLINE | ID: mdl-11698433

ABSTRACT

Infection of mice with the intracellular bacterium Listeria monocytogenes results in a strong CD8(+) T cell response that is critical for efficient control of infection. We used CD28-deficient mice to characterize the function of CD28 during Listeria infection, with a main emphasis on Listeria-specific CD8(+) T cells. Frequencies and effector functions of these T cells were determined using MHC class I tetramers, single cell IFN-gamma production and Listeria-specific cytotoxicity. During primary Listeria infection of CD28(-/-) mice we observed significantly reduced numbers of Listeria-specific CD8(+) T cells and only marginal levels of specific IFN-gamma production and cytotoxicity. Although frequencies were also reduced in CD28(-/-) mice during secondary response, we detected a considerable population of Listeria-specific CD8(+) T cells in these mice. In parallel, IFN-gamma production and cytotoxicity were observed, revealing that Listeria-specific CD8(+) T cells in CD28(-/-) mice expressed normal effector functions. Consistent with their impaired CD8(+) T cell activation, CD28(-/-) mice suffered from exacerbated listeriosis both after primary and secondary infection. These results demonstrate participation of CD28 signaling in the generation and expansion of Ag-specific CD8(+) T cells in listeriosis. However, Ag-specific CD8(+) T cells generated in the absence of CD28 differentiated into normal effector and memory T cells.


Subject(s)
Antigens, Bacterial/immunology , CD28 Antigens/physiology , Listeriosis/immunology , Lymphocyte Activation , T-Lymphocytes, Cytotoxic/immunology , Animals , CD28 Antigens/genetics , CD4-Positive T-Lymphocytes/immunology , Cells, Cultured , Cytotoxicity Tests, Immunologic , Interferon-gamma/biosynthesis , Interleukin-2/biosynthesis , Listeria monocytogenes/immunology , Listeriosis/microbiology , Mice , Mice, Knockout , Peptides/immunology
2.
J Virol ; 75(17): 8306-16, 2001 Sep.
Article in English | MEDLINE | ID: mdl-11483776

ABSTRACT

Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) mediate immunologic selection pressure by both cytolytic and noncytolytic mechanisms. Non cytolytic mechanisms include the release of beta-chemokines blocking entry of R5 HIV-1 strains. In addition, CD8(+) cells inhibit X4 virus isolates via release of as yet poorly characterized soluble factors. To further characterize these factors, we performed detailed analysis of CTL as well as bulk CD8(+) T lymphocytes from six HIV-1-infected individuals and from six HIV-1-seronegative individuals. Kinetic studies revealed that secreted suppressive activities of HIV-1-specific CTL and bulk CD8(+) T lymphocytes from all HIV-1-infected persons are significantly higher than that of supernatants from seronegative controls. The suppressive activity could be blocked by monensin and brefeldin A, was heat labile, and appeared in a pattern different from that of secretion of chemokines (MDC, I-309, MIP-1alpha, MIP-1beta, and RANTES), cytokines (gamma interferon, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor), and interleukins (interleukin-13 and interleukin-16). This suppression activity was characterized by molecular size exclusion centrifugation and involves a suppressive activity of >50 kDa which could be bound to heparin and a nonbinding inhibitory activity of <50 kDa. Our data provide a functional link between CD8(+) cells and CTL in the noncytolytic inhibition of HIV-1 and suggest that suppression of X4 virus is mediated through proteins. The sizes of the proteins, their affinity for heparin, and the pattern of release indicate that these molecules are not chemokines.


Subject(s)
Antiviral Agents/metabolism , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , HIV Infections/immunology , HIV-1/physiology , Proteins/metabolism , Antiviral Agents/chemistry , Chemokines, CC/genetics , Chemokines, CC/metabolism , Culture Media, Conditioned , Cytokines/genetics , Cytokines/metabolism , HIV Infections/virology , HIV Seronegativity/immunology , HIV-1/immunology , Humans , Proteins/chemistry , T-Lymphocytes, Cytotoxic/immunology , Virus Replication
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