Cellular protein is the source of cross-priming antigen in vivo

UMMS Affiliation

Department of Pathology



Document Type



Animals; Antigen Presentation; Cloning, Molecular; Cross-Priming; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Immunoglobulin G; Mice; Mice, Inbred Strains; Ovalbumin; Rabbits; Recombinant Proteins; Subcellular Fractions; T-Lymphocytes, Cytotoxic; Transfection


Life Sciences | Medicine and Health Sciences


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.

Rights and Permissions

Citation: Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3035-40. Epub 2004 Feb 20. Link to article on publisher's site

DOI of Published Version


Related Resources

Link to Article in PubMed

Journal Title

Proceedings of the National Academy of Sciences of the United States of America

PubMed ID