The lysosomal cysteine proteases in MHC class II antigen presentation

Authors

  • Lianne C. Hsing,

    1. Department of Immunology, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, WA, USA.
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  • Alexander Y. Rudensky

    Corresponding author
    1. Department of Immunology, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, WA, USA.
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* Alexander Rudensky
Department of Immunology
Howard Hughes Medical Institute
Box 357370, Seattle, WA 98195, USA
Tel.: +1 206 685 7644
Fax: +1 206 685 3612
E-mail: aruden@u.washington.edu

Abstract

Summary:  The endosomal pathway of antigen presentation leads to the display of peptides on major histocompatibility complex (MHC) class II molecules at the cell surface of antigen-presenting cells (APCs). The pathway involves two major steps, invariant chain degradation and antigen processing, which take place in the late endosomes/lysosomes. So far, of the known lysosomal proteases, only cathepsin L and cathepsin S have been shown to have a non-redundant role in endosomal presentation in vivo. Besides being engaged in the degradation of invariant chain, these enzymes also mediate the processing of antigens in distinct cell types. Surprisingly, these enzymes are active in different types of APCs, and this defined expression pattern seems to be enforced by regulatory mechanisms acting on multiple levels.

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