DR/CLIP (Class II-Associated Invariant Chain Peptides) and DR/Peptide Complexes Colocalize in Prelysosomes in Human B Lymphoblastoid Cells

• Published in: The Journal of immunology (1950) Vol. 160; no. 10; pp. 4696 - 4707
• Main Authors: Stang, Espen, Guerra, Carolyn B, Amaya, Miguel, Paterson, Yvonne, Bakke, Oddmund, Mellins, Elizabeth D
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.05.1998
• Subjects: Antigens, Differentiation, B-Lymphocyte - analysis; B-Lymphocytes - chemistry; Cell Line; Endosomes - chemistry; Histocompatibility Antigens Class II - analysis; HLA-D Antigens - analysis; HLA-DR Antigens - analysis; Humans; Immunohistochemistry; Lysosomes - chemistry
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.160.10.4696

In APCs, MHC class II molecules (MHC class II) bind antigenic peptides after HLA-DM mediated removal of CLIP. To characterize intracellular sites of peptide loading in human B lymphoblastoid cell lines, we conducted immunoelectron microscopy studies with Abs recognizing MHC class II associated with CLIP or bound peptide, respectively, together with Abs to HLA-DM and endocytic markers. The distribution of these molecules indicates that peptide binding occurs in compartments with characteristics of normal late endosomes, and in compartments that show characteristics of late endosomes, but are not detectably accessed by endocytosed BSA-gold. The latter compartments may represent or give rise to recycling vesicles that deliver peptide-loaded class II molecules to the cell surface. In addition, we have compared cells in which HLA-DM and HLA-DR interaction is defective with cells in which this interaction is intact, and find that DM/DR interaction is not required for the proper localization of either molecule to peptide-loading compartments.