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1: Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3035-40. Epub 2004 Feb 20.
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Cellular protein is the source of cross-priming antigen in vivo.

Shen L, Rock KL.

Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01655, USA.

Cross-priming is essential for generating cytotoxic T lymphocytes to viral, tumor, and tissue antigens that are expressed exclusively in parenchymal cells. In this process, the antigen-bearing parenchymal cells must somehow transfer their antigens to bone marrow-derived professional antigen-presenting cells. Although intact proteins, small peptides, or peptide-heat shock protein complexes can all be acquired and presented by antigen-presenting cells, the physiologically relevant form of antigen that is actually transferred from parenchymal cells and cross-presented in vivo is unknown and controversial. To address this issue we have investigated the ability of fibroblasts stably expressing chicken ovalbumin constructs targeted to different subcellular compartments to cross-prime cytotoxic T lymphocytes. Although these transfectants generated similar amounts of the immunogenic ovalbumin peptide, their cross-priming activity differed markedly. Instead, the cells cross-priming ability correlated with their steady-state levels of ovalbumin protein and/or the physical form/location of the protein. Moreover, in subcellular fractionation experiments, the cross-priming activity colocalized with antigenic protein. In addition, depletion of intact protein antigen from these cell fractions eliminated their cross-priming activity. In contrast, the major heat shock protein candidates for cross-presentation were separable from the cell's main sources of cross-priming antigen. Therefore, cellular proteins, rather than peptides or heat shock protein/peptide complexes, are the major source of antigen that is transferred from antigen-bearing cells and cross-presented in vivo.

Publication Types:
PMID: 14978273 [PubMed - indexed for MEDLINE]

PMCID: PMC365740