Excessive degradation of intracellular protein in macrophages prevents presentation in the context of major histocompatibility complex class II molecules
Article first published online: 6 DEC 2005
Copyright © 1997 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
European Journal of Immunology
Volume 27, Issue 6, pages 1506–1514, June 1997
How to Cite
Brazil, M. I., Weiß, S. and Stockinger, B. (1997), Excessive degradation of intracellular protein in macrophages prevents presentation in the context of major histocompatibility complex class II molecules. Eur. J. Immunol., 27: 1506–1514. doi: 10.1002/eji.1830270629
- Issue published online: 6 DEC 2005
- Article first published online: 6 DEC 2005
- Manuscript Accepted: 9 APR 1997
- Manuscript Revised: 4 APR 1997
- Manuscript Received: 3 JAN 1997
- Medical Research Council U.K.
- studentship from the Medical Research Council, U.K.
- British-German Academic Research Collaboration (ARC) programme
- Antigen presentation;
- Lysosomal degradation;
- Major histocompatibility complex class II presentation pathway;
- Major histocompatibility complex class II-restricted T cells
The endogenous major histocompatibility complex (MHC) class II presentation pathway allows biosynthesized, intracellular antigens access for presentation to MHC class II-restricted T cells. This pathway has been well documented in B cells and fibroblasts, but may not be universally available in all antigen-presenting cell types. This study compares the ability of different antigen-presenting cells, expressing endogenous C5 protein (fifth component of mouse complement) as a result of transfection, to present their biosynthesized C5 to MHC class II-restricted T cells. B cells and fibroblasts expressing C5 were able to present several epitopes of this protein with MHC class II molecules, whereas macrophages were unable to do so, but readily presented C5 from an extracellular source. However, macrophage presentation of endogenous C5 could be achieved when they were treated with low doses of the lysosomotropic agent ammonium chloride. In the presence of an inhibitor of autophagy, presentation of endogenous C5 was abrogated, indicating that biosynthesized C5 is shuttled into lysosomal compartments for degradation before making contact with MHC class II molecules. Taken together, this suggests that proteolytic activity in lysosomes of macrophages may be excessive, compared with fibroblasts and B cells, and destroys epitopes of the C5 protein before they can gain access to MHC class II molecules. Thus, there are inherent differences in presentation pathways between antigen-presenting cell types; this could reflect their specialized functions within the immune system with macrophages focussing preferentially on internalization, degradation, and presentation of extracellular material.