Illustration of a dendritic cell (blue) processing spike (S) proteins from the SARS-CoV-2 virus, the cause of the respiratory disease covid-19. Dendritic cells are a component of the body's immune system. The cell gets it name from the long membrane extensions off the cell body, which look like the dendrites of a nerve cell. Dendritic cells are antigen-presenting cells (APCs), that is, they present pathogens or foreign molecules (antigens) to other cells of the immune system to be eliminated. The S proteins bind to angiotensin-converting enzyme 2 (ACE2) receptors on human cells to infect them. It is a target for the body's immune system and is used in vaccines against the virus.