Tuesday, June 16, 2020

Ch 4. A favorable outcome - immunity to coronaviruses in context of COVID-19

Reading time: approx 3:29 minutes
Readability: Grade 8

Today's chapter discusses the situation where we overcome the virus infection. In case of coronavirus infection, this is the most common scenario where infections are without symptoms or have mild to moderate symptoms and disease does not progress.

In the previous sections, we have seen infected cells make a protein to boost defenses. They (infected cells) and immune cells also release other chemicals causing a fever. Fever is important to increase metabolism activity of cell and slow virus production. Many other proteins (called interleukins) activate other parts of the immune system. The scout cells (Ch 3), deliver pieces of virus/infected cells to special adaptive immune cells. The CD4 helper cells produce many chemicals needed to fight virus. Some of these increase the killing capacity of innate killer cells. Others direct antibody making cells to start making anti-virus antibodies. Yet another group, powers up the advanced killer cells to end virus containing cells. Killing virus infected cells is similar to a controlled burn to stop a forest fire. By killing cells infected with virus, the virus cannot spread.

Summary of events of a successful elimination of viral infection (connect the numbers with the detail below)

An appropriate response to viral infections (see figure)

1) Early responses can hold off the virus from spreading

2) Interferons produced by cells can boost and get rid of virus and virus infected cells.

3) Innate troops can cause activation of cell damage systems to limit virus spread

4) Scout of innate system pick up dead/dying cells with dead virus parts

5) These scouts deliver the virus parts to adaptive/advanced immune response cells

6) Helper cells coordinate and command the a virus specific response

7) Helper cells boost activation of cell damage systems of innate troops and killers

8) Helper cells tell antibody making cell to start making anti-virus antibodies. Antibodies can block and neutralize virus outside cells.

9) Helper cells boost killing power of killer cells, so they

10) Rid of virus and the virus infected cell.


If everything goes according to plan, the viral infection (be it coronavirus or flu virus), stops. The immune system had done a good job of eliminating the virus. Some parts of immune system save the information as memory cells in case this virus attacks us again.

References:
- Braciale, Thomas J., Jie Sun, and Taeg S. Kim. "Regulating the adaptive immune response to respiratory virus infection." Nature Reviews Immunology 
- Swain, Susan L., K. Kai McKinstry, and Tara M. Strutt. "Expanding roles for CD4+ T cells in immunity to viruses." Nature Reviews Immunology 12.2 (2012): 136-148.2.4 (2012): 295-305.
- Prompetchara, Eakachai, Chutitorn Ketloy, and Tanapat Palaga. "Immune responses in COVID-19 and potential vaccines: Lessons learned from SARS and MERS epidemic." Asian Pac J Allergy Immunol 38.1 (2020): 1-9.


Next section:
Previous section: Ch 3. Meet your defense forces - immunity to coronaviruses in context of COVID-19

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