Autophagy protects against pathogen invasion

 Autophagy is activated under different pressures or stimuli. For cells, infection is also a stimulus. Virus and bacterial infection are important causes of human disease or death. Many studies have confirmed that autophagy can be used as a defense mechanism for bacteria and viruses to protect host cells. Autophagy can eliminate the bacteria that exist in the cell. The pathogens in the cell are like Mycobacterium tuberculosis. After being swallowed by macrophages, they can survive and replicate in the host cell by inhibiting the maturation of the phagosome. At this time, the role of autophagy is to overcome the inhibition of mycobacteria on the maturation of phagosomes, making mycobacteria unable to survive in host cells, and reducing the chance of tuberculosis.

In addition, it was also found that autophagy can eliminate group A streptococci that escaped to the cytoplasm after being phagocytosed, and can identify damaged Salmonella inclusion bodies, and then wrap the typhoid bacillus and eliminate it. Although autophagy can help host cells eliminate bacteria, it is currently known that some bacteria in cells can survive and replicate without being eliminated by autophagy, such as Shigella flexneri and Listeria.

Autophagy also uses different modes of action to play a role in fighting viruses. When fighting the virus, the cell will produce the first type interferon to inhibit the replication of the virus. Scientists have discovered for the first time that when the vesicular stomatitis virus infects the cell, the autophagosome can help the cell identify the virus particle, and then induce the first type of antiviral interference Inhibit the virus. In addition, autophagy will also express viral proteins in infected cells to the cell surface, allowing patrolling immune cells to discover and then clear the infected cells to reduce the chance of other cells being infected.

Of course, just like fighting against bacteria in cells, autophagosomes can also encapsulate viruses in them, and then use enzymes in lysosomes to eliminate virus proteins or genetic molecules to inhibit virus replication, such as against herpes viruses. On the other hand, some viruses use autophagy to promote their growth and replication in cells, such as dengue fever virus, herpes zoster virus, human papilloma virus, hepatitis B virus, influenza virus, etc. It can be seen that autophagy plays different roles in the growth and replication of different pathogens.