In just seven months, beginning in December
2019, the novel coronavirus has infected more
than 8 million people worldwide.
The human immune system resists, inhibits,
and kills a broad range of pathogens including
the novel coronavirus.
Therefore, the immune system is vital to the
human body’s natural defense against pathogens
by protecting the body from potential threats
posed by the coronavirus.
Unfortunately, the immune system is not impenetrable.
Despite the body’s continuous external protection
system, the coronavirus can still break through.
One way is through inhaling the airborne coronavirus
into sac-like structures inside the lungs.
These structures are known as the alveoli.
So, what exactly are the alveoli?
The alveoli are composed of cells that are
responsible for the exchange of oxygen and
carbon dioxide, known as pneumocyte cells.
They are surrounded by pulmonary capillaries
containing deoxygenated blood.
The inhaled oxygen diffuses into the capillaries
from the alveoli.
The normal functioning of the alveoli is detrimental
in the presence of the coronavirus.
The coronavirus’s spike protein binds onto
the Type II pneumocyte cells in the alveoli,
inhibiting the normal functions of the cells.
As soon as the immune system is alerted, it
sends macrophages, one of the crucial white
blood cells that is responsible for the neutralization
of the coronavirus infected cells.
Meanwhile, the macrophages produce cytokines
that send other white blood cells, specifically
neutrophils and lymphocytes, into the affected
areas.
These white blood cells utilize small signaling
proteins, including cytokines, to initiate
the immune-mediated cell death of the alveolar
cells.
However, the overproduction of cytokines leads
to the structurally deficient break in pulmonary
capillaries, causing shrinkage and holes on
the capillaries.
It is through these holes that the plasma
leaks into the alveoli and prohibits the normal
diffusion of oxygen.
It is similar to this barrier created between
the leaves of a tree and the air around it,
carbon dioxide would not be able to diffuse
into the leaves.
What this means is that fewer functional alveoli
result in oxygen deficiency, making breathing
more difficult.
As the coronavirus spreads to other structural
units of the lungs, the patient begins to
have severe medical complications and usually
requires a ventilator.
A ventilator supplies oxygen to the patient,
similar to the process of the alveoli.
It is not until the immune system successfully
breaks down the coronavirus that the alveoli
regain their function.
Due to the high mortality rate of patients
requiring ventilators, scientists are developing
vaccines to protect against COVID-19.
Vaccines generally contain an alternative
agent that resembles a disease-causing pathogen.
They are prepared from weakened or killed
forms of the pathogen.
After introducing the vaccine, the stimulated
immune system promotes the biosynthesis of
antibodies that bind onto the spike proteins
of the coronavirus, neutralizing it.
Thus, vaccines serve as a well-developed tool
with remarkable medical importance.
They might become a treatment to the severe
immune system disease caused by the novel coronavirus.
Will there ever come a time when our immune
systems are impenetrable?
That’s the challenge of the future!
Thanks for watching!
