A curious researcher recently asked us to suggest suitable antigens that could stimulate IFNγ producing CD8+ T cells.
The short answer: Virus proteins.
But as with anything in immunology and virology, there is a longer, more complicated explanation as well.
Protein Antigens vs. Peptide Antigens
CD8+ T cells normally recognize antigens that are produced within cells, making them ideal for killing cells infected by viruses or other intracellular parasites. This makes virus proteins — such as CMV antigens and HPV antigens — the best choice for such experiments.
The problem with proteins, however, is that they are usually presented to T cells on class II major histocompatibility complex (MHC) molecules, whereas class I MHC are typically required to present antigens to cytotoxic CD8+ T cells. This MHC mismatch can cause your IFNγ stimulation attempts to fail.
If you must use protein antigens, consider using dendritic cells as antigen-presenting cells. Dendritic cells will present some antigen through the class I pathway. Alternatively, try expressing the antigen of interest in APC by transient transduction. You can also check for literature on methods used to get the protein into the cytoplasm.
Protein antigens also have the distinct advantage of being able to perform in a wider range of applications, including Western Blot, ELISA, Sandwich ELISA, Direct Bind ELISA, Flow Cytometry, IHC, and Functional Assays.
If you choose peptide antigens for IFNγ stimulation, you should consider pooled peptides.
Individual peptides only activate a fraction of the CD8+ T cells found in PBMC. Pools of peptides, however, can achieve activation of many more CD8+ cells in the PBMC.
For example, there are control peptide pools from CMV, EBV, and influenza. If your interest is a specific protein antigen, you can consider creating your own peptide pool that covers the length of the protein. If you have a small protein, this can be the best way to go.
Peptide antigens are best when targeting a specific, known immune response.
Antigens and Peptides for Research
We have a variety of research-ready antigens and peptides for you, including CMV, MART-1, HPV, HER2/neu, M1, HSV, NY-ESO, Proinsulin, Tetanus Toxoid, WT1, and MBP. If you need help determining the best fit for your research, we’re here to help.