Coronavirus pathophysiology | Pneumonia caused by coronavirus
Channel: Physiology Open
Date: 2020-04-05

Pathophysiology of coronavirus

Most common way for the coronavirus to enter our body is through respiratory tract i.e via mouth or nose. If we are exposed to more dose of the coronvirus virus or in case our immune system is not strong , the coronavirus manages to reach to the alveoli. Further outcome depends on how effectively our immune system fights against corona virus. 

Role of macrophages
Once the virus is in alveoli, macrophages ingest the virus. Macrophages present the antigen to Helper T cells. Also they release certain chemical known as IL-1 and TNF alpha.

The chemicals IL-1 and TNF alpha,  increase the permeability of blood vessels causing fluid to leak out of the vessels. Also, along with that neutrophils, T cells  start migrating to outside the blood vessel to help the macrophages leading to development of pneumonia.

In the meantime, some virion particles enter into cells and start multiplying. .
Whenever the cells are infected with virion, the immune system starts various mechanisms:
1. Helper T cells and infected cells produce interferons.  These interferons act on the infected cell itself as well as on nearby cells via JAK-STAT pathway.  In infected cells, they inhibit viral replication. On nearby cells, they make them resistant to infection by virus. 

2. Helper T cells activate cytotoxic T cells which can kill the virus infected cells.

But coronavirus has a mechanism to evade this immune attack.

1. Coronavirus multiply within  Double Membrane Vesicles (DMVs)  so the cells are not able to identify that they are infected with the virus  and thus are unable to produce interferons. 
2. The interferons released by T cells also cannot act because the virus blocks the activation of this interferon system by blocking the JAK-STAT pathway. 

So the virus keeps on multiplying and hence increasing the virus load tremendously.

As virus multiplies, it releases more and more viruses , infecting more and more cells, confusing more and more macrophages which end up activating immune system in an uncontrolled manner and hence releasing these and many other chemicals which keep on exaggerating the pneumonia. 

Because of this diffusion of oxygen is affected causing hypoxemia.

So that’s how people infected with coronavirus succumb to the infection.


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