Peptide Antigens in Immune Responses

Peptide antigens play a critical role in the immune system’s ability to recognize and respond to pathogens. These antigens are typically short fragments of proteins that are presented on the surface of cells by major histocompatibility complex, MHC, molecules. Peptide-MHC complexes are recognized by T-cell receptors, TCRs, on the surface of T-lymphocytes, triggering immune responses that lead to the destruction of infected or abnormal cells.

Presentation by MHC Molecules

MHC molecules present peptide antigens to T-cells in two distinct classes. MHC class I molecules present intracellular peptides to cytotoxic T-cells, which are responsible for recognizing and killing infected or cancerous cells. MHC class II molecules, on the other hand, present extracellular peptides to helper T-cells, which assist in coordinating broader immune responses, including the activation of B-cells for antibody production.¹

Role in Vaccine Development

Peptide antigens are extensively studied for use in vaccine development, where specific epitopes, peptide fragments recognized by immune cells, are designed to stimulate protective immune responses. These epitope-based vaccines offer advantages over traditional vaccines, as they can be highly specific, avoiding unwanted immune reactions and improving safety profiles. For example, peptide-based vaccines have shown promise in targeting pathogens like HIV, hepatitis C, and influenza, as well as in cancer immunotherapy.²

Advanced Topic: Peptide-Based Immunotherapies

Peptide-based immunotherapies are also being developed to modulate immune responses in autoimmunity and cancer. In cancer, peptides can be used to stimulate T-cell responses against tumor-specific antigens, promoting the immune system’s ability to recognize and eliminate cancer cells. In autoimmune diseases, tolerogenic peptides are being studied to suppress unwanted immune responses against self-antigens.³

Conclusion

Peptide antigens are at the forefront of immunological research, offering significant potential for the development of highly specific vaccines and immunotherapies. By leveraging the immune system’s ability to recognize peptide-MHC complexes, researchers can design targeted interventions to prevent or treat infectious diseases and cancers.

Citations and Links

1. Janeway, Charles A., et al. Immunobiology: The Immune System in Health and Disease. 8th ed., Garland Science, 2012.

2. Neefjes, Jacques, et al. “Towards a Systems Understanding of MHC Class I and MHC Class II Antigen Presentation.” Nature Reviews Immunology, vol. 11, no. 12, 2011, pp. 823–836. doi:10.1038/nri3084.

3. Schumacher, Ton N., and Robert D. Schreiber. “Neoantigens in Cancer Immunotherapy.” Science, vol. 348, no. 6230, 2015, pp. 69-74. doi:10.1126/science.aaa4971.