Alcoholic patients have a high incidence of hepatitis C virus （HCV） infection. Alcohol consumption enhances the severity of the HCV disease course and worsens the outcome of chronic hepatitis C. The accumulation of ...Alcoholic patients have a high incidence of hepatitis C virus （HCV） infection. Alcohol consumption enhances the severity of the HCV disease course and worsens the outcome of chronic hepatitis C. The accumulation of virally infected cells in the liver is related to the HCV- induced inability of the immune system to recognize infected cells and to develop the immune responses. This review covers the effects of HCV proteins and ethanol on major histocompatibility complex （MHC） class Ⅰ- and class Ⅱ-restricted antigen presentation. Here, we discuss the liver which functions as an immune privilege organ; factors, which affect cleavage and loading of antigenic peptides onto MHC class I and class ~I in hepatocytes and dendritic cells, and the modulating effects of ethanol and HCV on antigen presentation by liver cells. Altered antigen presentation in the liver limits the ability ＇of the immune system to clear HCV and infected cells and contributes to disease progression. HCV by itself affects dendritic cell function, switching their cytokine profile to the suppressive phenotype of interleukin-10 （IL-10） and transforming growth factor beta （TGFβ） predominance, preventing cell maturation and allostimulation capacity. The synergistic action of ethanol with HCV results in the suppression of MHC class Ⅱ-restricted antigen presentation. In addition, ethanol metabolism and HCV proteins reduce proteasome function and interferon signaling, thereby suppressing the generation of peptides for MHC class I -restricted antigen presentation. Collectively, ethanol exposure further impairs antigen presentation in HCV-infected liver cells, which may provide a partial explanation for exacerbations and the poor outcome of HCV infection in alcoholics.展开更多
Presentation of antigenic peptide to T cells by major histocompatibility complex (MHC) class I molecules is the key to the cellular immune response.Non-self intracellular proteins are processed into short peptides and...Presentation of antigenic peptide to T cells by major histocompatibility complex (MHC) class I molecules is the key to the cellular immune response.Non-self intracellular proteins are processed into short peptides and transported into endoplasmic reticulum (ER) where they are assembled with class I molecules assisted by several chaperone proteins to form trimeric complex.MHC class I complex loaded with optimised peptides travels to the cell surface of antigen presentation cells to be recognised by T cells.The cells presenting non-self peptides are cleared by CD8 positive T cells.In order to ensure that T cells detect an infection or mutation within the target cells the process of peptide loading and class I expression must be carefully regulated.Many of the cellular components involved in antigen processing and class I presentation are known and their various functions are now becoming clearer.Cellular & Molecular Immunology.2004;1(1):22-30.展开更多
Traditionally,macroautophagy(autophagy)is viewed as a pathway of cell survival.Autophagy ensures the elimination of damaged or unwanted cytosolic components and provides a source of cellular nutrients during periods o...Traditionally,macroautophagy(autophagy)is viewed as a pathway of cell survival.Autophagy ensures the elimination of damaged or unwanted cytosolic components and provides a source of cellular nutrients during periods of stress.Interestingly,autophagy can also directly intersect with,and impact,other major pathways of cellular function.Here,we will review the contribution of autophagy to pathways of antigen presentation.The autophagy machinery acts to modulate both MHCⅠ and MHCⅡ antigen presentation.As such autophagy is an important participant in pathways that elicit host cell immunity and the elimination of infectious pathogens.展开更多
基金Supported by Development funds from Section of Gastroenterology/Hepatology, Internal Medicine, University of Nebraska Medical Center
文摘Alcoholic patients have a high incidence of hepatitis C virus （HCV） infection. Alcohol consumption enhances the severity of the HCV disease course and worsens the outcome of chronic hepatitis C. The accumulation of virally infected cells in the liver is related to the HCV- induced inability of the immune system to recognize infected cells and to develop the immune responses. This review covers the effects of HCV proteins and ethanol on major histocompatibility complex （MHC） class Ⅰ- and class Ⅱ-restricted antigen presentation. Here, we discuss the liver which functions as an immune privilege organ; factors, which affect cleavage and loading of antigenic peptides onto MHC class I and class ~I in hepatocytes and dendritic cells, and the modulating effects of ethanol and HCV on antigen presentation by liver cells. Altered antigen presentation in the liver limits the ability ＇of the immune system to clear HCV and infected cells and contributes to disease progression. HCV by itself affects dendritic cell function, switching their cytokine profile to the suppressive phenotype of interleukin-10 （IL-10） and transforming growth factor beta （TGFβ） predominance, preventing cell maturation and allostimulation capacity. The synergistic action of ethanol with HCV results in the suppression of MHC class Ⅱ-restricted antigen presentation. In addition, ethanol metabolism and HCV proteins reduce proteasome function and interferon signaling, thereby suppressing the generation of peptides for MHC class I -restricted antigen presentation. Collectively, ethanol exposure further impairs antigen presentation in HCV-infected liver cells, which may provide a partial explanation for exacerbations and the poor outcome of HCV infection in alcoholics.
文摘Presentation of antigenic peptide to T cells by major histocompatibility complex (MHC) class I molecules is the key to the cellular immune response.Non-self intracellular proteins are processed into short peptides and transported into endoplasmic reticulum (ER) where they are assembled with class I molecules assisted by several chaperone proteins to form trimeric complex.MHC class I complex loaded with optimised peptides travels to the cell surface of antigen presentation cells to be recognised by T cells.The cells presenting non-self peptides are cleared by CD8 positive T cells.In order to ensure that T cells detect an infection or mutation within the target cells the process of peptide loading and class I expression must be carefully regulated.Many of the cellular components involved in antigen processing and class I presentation are known and their various functions are now becoming clearer.Cellular & Molecular Immunology.2004;1(1):22-30.
基金supported by a National Health and Medical Research Council of Australia Career Development Award.
文摘Traditionally,macroautophagy(autophagy)is viewed as a pathway of cell survival.Autophagy ensures the elimination of damaged or unwanted cytosolic components and provides a source of cellular nutrients during periods of stress.Interestingly,autophagy can also directly intersect with,and impact,other major pathways of cellular function.Here,we will review the contribution of autophagy to pathways of antigen presentation.The autophagy machinery acts to modulate both MHCⅠ and MHCⅡ antigen presentation.As such autophagy is an important participant in pathways that elicit host cell immunity and the elimination of infectious pathogens.
