How does the immune system work? Will there be #COVID19 vaccines? @BioRender & I put together ‘immunology 101 tweetorial for non-immunologists’. @jerryguartist, @shizaoki, @JungHeeSciViz also made this accompanying video. Please share widely! (1/n)

The immune system protects the host from invading pathogens through 2 layers: the innate and adaptive immunity. Innate immunity acts within minutes to remove the pathogen. Adaptive immunity takes days/wks but is specific & long lived, and is the basis for #vaccines. (2/n)

Innate immunity starts by triggering sensors that detect unusual molecules or activities, known as pattern recognition. Once microbial patterns are detected by these sensors ( #PRR), they trigger immediate alarm through secretion of #cytokines and #interferons. (3/n)

Interferons bind to receptors on various cells around them to help put up guard against further invasion; induce death of infected cells to stop further virus production; and flag white blood cells to be recruited to the site of infection to attack the invaders. (4/n)

However, when cytokines are triggered without breaks, they can cause damage to the cells responding to the cytokines, and shut down the function of the organs. This is known as cytokine storm, which mediates severe disease including #COVID19. (5/n)

The T and B lymphocytes, the key players of adaptive immune system, require education by dendritic cells (DC) that survey the tissue for invaders. DCs detect pathogens, migrate to the draining lymph nodes and educate T and B cells to become effector cells. (6/n)

Once they reach the target tissue, killer T cells detect specific virus fragments on the surface of infected cells and destroy them, eliminating virus factory. Antibodies secreted by B cells bind to the surface of the virus and block host entry (neutralizing antibodies). (7/n)

B cells also secrete non-neutralizing antibodies that call in other white blood cells (NK cells) to kill virus-infected cells. NK cells are also professional killer cells. They use guidance from antibodies to target their weapons against infected cells. (8/n)

What’s about the adaptive immune system is that both T and B cells become memory cells. The second time you encounter the same virus, memory B cells will produce much quicker & higher levels + quality of antibodies. Memory T cells provide quick and robust protection. (9/n)

Some B cells become plasma cells that secrete specific antibodies for years. If you were vaccinated as a child, you are likely to have antibodies to the vaccine antigens decades later. Antibodies will bind to the invading pathogen immediately and block their spread. (10/n)

Duration of antibodies depends on the type of pathogens. For measles, lifetime. For common cold coronaviruses, 1-2 years. However, even if Ab is low, memory B and T cells can re-ignite antibody and killer cells during reinfection to keep you from becoming ill. (11/n)

The safest and most reliable way to achieve immunity is through vaccination. Vaccines are designed to trigger robust and long-lasting immunity and can provide superior immunity to that achieved by natural infection. It is the only safe way to develop herd immunity. (12/n)

Vaccines can target the antibody and T cell to the Achilles heel of the virus and enhance immunity with adjuvants and boosters. They can also bypass viral evasion tactics to induce stronger immunity than natural infection.
Thanks for reading (end) https://biorender.com/covid-vaccine-tracker