protective antigen

Protective antigen (PA) is a protein that plays a crucial role in the pathogenicity of some bacteria, particularly Bacillus anthracis, the agent that causes anthrax. It helps the bacterium attach to host cells and facilitates the delivery of toxic components into those cells. In vaccines, protective antigen is used to provoke an immune response without causing disease, allowing the body to recognize and fight the actual bacteria if exposed in the future. Essentially, it acts as a key that helps the bacteria enter cells, while in vaccines, it primes the immune system to respond effectively.