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Antigen Presentation

  • Julius M. Cruse
  • Robert E. Lewis

Abstract

Tlymphocytes recognize antigens only in the context of self-MHC molecules on the surface of accessory cells. During processing, intact protein antigens are degraded into peptide fragments. Most epitopes that T cells recognize are peptide chain fragments. B cells and T cells often recognize different epitopes of an antigen leading to both antibody and cell-mediated immune responses. Before antigen can bind to MHC molecules, it must be processed into peptides in the intracellular organelles. CD4+ helper T lymphocytes recognize antigens in the context of class II MHC molecules, a process known as class II MHC-restriction. By contrast, CD8+ cytotoxic T lymphocytes recognize antigens in the context of class I molecules, which is known as class I MHCrestriction. Following the generation of peptides by proteolytic degradation in antigen-presenting cells, peptideMHC complexes are presented on the surface of antigen-presenting cells where they may be recognized by T lymphocytes. Antigens derived from either intracellular or extra-cellular proteins may be processed to produce peptides from either self or foreign proteins that are presented by surface MHC molecules to T cells. In the class II MHC processing pathway, professional antigen-presenting cells, such as macrophages, dendritic cells or B lymphocytes incorporate extra-cellular proteins into endosomes where they are processed (Figures 1 and 2). Enzymes within the vesicles of the endosomal pathway cleave proteins in the acidic environment.

Keywords

Antigen Presentation Invariant Chain Dendritic Reticulum Cell Histocompatibility Molecule Present Exogenous Antigen 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Julius M. Cruse
    • 1
  • Robert E. Lewis
    • 1
  1. 1.Department of Pathology, Mississippi Methodist Rehabilitation CenterUniversity of Mississippi Medical CenterJacksonUSA

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