期刊
EUROPEAN JOURNAL OF IMMUNOLOGY
卷 35, 期 12, 页码 3442-3451出版社
WILEY
DOI: 10.1002/eji.200535320
关键词
cathepsin D; cathepsin E; antigen processing; MHC class II; destructive processing
类别
资金
- Wellcome Trust Funding Source: Medline
Whether specific proteases influence MHC class II antigen presentation is still not clearly defined. Cathepsin D, one of the most abundant lysosomal proteases, is thought to be dispensable for MHC class II antigen presentation, yet in vitro digestions of antigen substrates with endosomes/lysosomes from antigen-presenting cells sometimes reveal a dominant role for pepstatin-sensitive aspartyl proteases of which cathepsin D is the major representative. We tested whether the aspartyl protease substrate myoglobin requires cathepsin D activity for presentation to T cells. Surprisingly, in dendritic cells (DC) lacking cathepsin D, presentation of two different myoglobin T cell epitopes was enhanced rather than hindered. This paradox is resolved by the finding that pepstatin-sensitive myoglobin processing activity persists in lysosomes from cathepsin D-null DC and that this reduced activity, most likely due to cathepsin E, is closer to the optimum level required for myoglobin antigen presentation. Our results indicate redundancy among lysosomal aspartyl proteases and show that while processing activities can be productive for MHC class II T cell epitope generation at one level, they can become destructive above an optimal level.
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