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Endolysosomal Processing of Exogenous Antigen into Major Histocompatibility Complex Class I‐Binding Peptides
Author(s) -
Chen L.,
Jondal M.
Publication year - 2004
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.2004.01426.x
Subject(s) - antigen processing , major histocompatibility complex , monoclonal antibody , brefeldin a , chemistry , mhc class i , microbiology and biotechnology , antigen , biology , biochemistry , antibody , golgi apparatus , cell , immunology
An alternative endolysosomal pathway has recently been suggested for the processing of MHC‐I‐binding peptides, and peptide/MHC‐I complexes have been demonstrated in this compartment. However, it remains unclear where in the antigen‐presenting cells such peptides are processed, in the endolysosomes themselves or in the proteasomal complex. Here, we have investigated this using monoclonal antibodies specific for the immunodominant SIINFEKL/Kb complex (25‐D1) or for the carbohydrate part of Db‐ or Kb‐binding glycopeptides in combination with inhibitors for classical and endolysosomal MHC‐I‐processing pathways. Alternative processing was detected in both wt and TAP1 –/– immature DC (iDC) as the expression of SIINFEKL/Kb complexes on the surface of OVA‐treated cells in the presence of Brefeldin A (BFA) or lactacystin and their absence in the presence of the lysosomotropic amines ammonium chloride, chloroquine and methylamine. Internalized Db‐ and Kb‐binding glycopeptides, detected with high specificity using an anti‐galabiose (Gal2) monoclonal antibody, were found to appear on the cell surface of BFA‐treated cells after intracellular MHC‐I‐binding. Peptide exchange in Kb was demonstrated as the gradual appearance of SIINFEKL/Kb complexes on BFA‐treated cells which earlier had been saturated with another Kb‐binding peptide. Our data support the presence of a fully functional endolysosomal processing pathway in iDC guided by the chaperone function of MHC‐I molecules.