Chemical Immunology: Click Chemistry Tools for Antigen Presentation

T-cell activation marks one of the pivotal points in the immune response, where a dendritic cell presents short peptides derived from exogenous antigens to a T-cell. The antigens taken up by dendritic cells require extensive degradation prior to loading by proteases present in the endo-lysosomal system and other organelles. The precise molecular mechanisms of the degradation pathway have largely remained elusive, which has been complicated by challenges in studying this phenomenon. Particularly, either T-cells are used that can quantify the appearance of antigen at the end of the process, or reporter proteins are used that model only the early part of the process where the antigens are still intact. Further, the fluorophore of fluorescent antigens changes the biophysical behavior of the antigens to such an extent, that they no longer behave like the parent antigen. By attempting to visualize degradation in a non-endogenous manner, the information obtained may or may not be biologically meaningful. One possible way to overcome these challenges is through click chemistry. Click chemistry, or bioorthogonal chemistry, is the selective chemical coupling reaction performed in a cell, organ, or animal. The technique is based on the modification of cells, proteins, drugs, or nutrients with very small chemical groups (i.e., 1-3 atoms). At the end of a biological reaction, these functional groups can react with a detectable group. The main advantage is that the detectable group does not change the biology of the molecule of interest, so that biological processes can be monitored. In this talk, Dr. van Kasteren will outline the use of click chemistry-based approaches to study degradation following T-cell activation. He will describe its application to the study of dendritic cells and their interaction with antigens and pathogens, as well as the use of click chemistry to study nutrient uptake. This webinar should provide the listener a good starting point to begin implementing these approaches in their biological workflows. Key discussion topics include: • Facile workflows and click chemistry-based approaches to study bacterial and antigen degradation in immune cells, with a focus on auto-antigen processing • Technology to visualize host-pathogen interactions in the cell • How click chemistry can be used to study live-cell nutrient uptake