In general, exogenous proteins are processed by antigen-presenting cells in the endosomes for major histocompatibility complex (MHC) class II presentation to CD4+ T cells, while proteins synthesized endogenously are processed in the cytoplasm for MHC class I presentation to CD8+ T cells. However, it is recognized that exogenous proteins can be processed for MHC class I presentation also, and evidence in favour of alternatives to the conventional MHC class I processing and presentation pathway is accumulating. Here, we show that exogenous recombinant influenza A virus nucleoprotein (rNP) is processed for MHC class I presentation to CD8+ cytotoxic T lymphocytes (CTL) by EBV-transformed, B-lymphoblastoid cell lines (B-LCL). Processing of rNP for HLA-B27-associated presentation seemed to follow the conventional MHC class I pathway predominantly, as presentation was diminished in the presence of lactacystin and brefeldin A, but was less sensitive to chloroquine and NH4Cl. HLA-B27-associated presentation was also observed using cells lacking a functional transporter associated with antigen processing, suggesting that alternative pathways may be exploited for processing of rNP.

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Clinical and Experimental Immunology
Erasmus MC: University Medical Center Rotterdam

Voeten, J. T. M., Rimmelzwaan, G., Nieuwkoop, N., Osterhaus, A., & Fouchier, R. (2001). Antigen processing for MHC class I restricted presentation of exogenous influenza A virus nucleoprotein by B-lymphoblastoid cells. Clinical and Experimental Immunology, 125(3), 423–431. doi:10.1046/j.1365-2249.2001.01613.x