Infection vs Immunity

 

The everyday Battle of the Immune system

Can’t think of a more relevant topic for the times of now. Enter, the pandemic; as Coronavirus has spread to every corner of the world, the topics of infection and immunity are as popular as can be. With people arguing whether a vaccine is the cure or if it’s the disease and the true cure is Garlic extract.

The conception of viruses is still mostly a mystery, there are multiple theories on the conception of viruses however, the two interesting ones are that viruses arose from genetic elements that gained the ability to move between cells and that viruses are remnants of cellular organisms. Viruses aren’t going anywhere anytime soon, and humans have to bear with these cell-less and deadly pests. Though, they aren’t all bad as you can argue they serve as nature’s metal solution to the increasing population problem and humans have also found ways to manipulate them to be used as pesticides and the like. Regardless, they are a reality that we have to live with, every day. 

For most of our lives, we stay unaware of the pesky virus invasions that happen in our body day-to-day. Everyday infections are attributed to being the result of mere chance, exposure, and invasion of viral agents. However, now compelling arguments are made that at least in the case of the more severe forms of these infections, invading viruses have taken advantage of a hidden flaw in the defense of our normal immunity.  In fact, in people who are afflicted with immunodeficiency, there is a correlation with the likelihood of cancer development.

If the human is infected and he/she lives to fight another day, he/she will become immune to the virus for at least a significant period of time; meaning they have developed an ability to resist the disease. In exposure to the virus, they will only develop minor symptoms if they develop any symptoms at all that is.

Now, you can give flak to Disney movies all you want and say they are targeted for kids, but you got to appreciate the scientific thought put behind them and, in this article, as I discuss infection and immunity, I will be putting some sneaky references to Osmosis Jones to keep things exciting.

Infection

Infection refers to the invasion and growth of germs in the body. The germs may be bacteria, viruses, yeast, fungi, or other microorganisms. To understand viral infections, we need to understand viruses:

 

Understanding Viruses

In the movie, Osmosis Jones, ‘Thrax’ is the big baddie virus; so much so as the infamous Ebola can’t hold a candle to him. The virus makes his way into the person’s when he eats a boiled egg dropped in a chimpanzee habitat. And so, the virus has ‘awoken’ in the stomach to be “the baddest illness” the world has ever seen. Viruses are just a piece or strand of genetic information. The ‘awakening’ mention above, refers to the incubation of a virus: a virus cannot reproduce until it has attached to a cell, it attaches to cells using receptors that connect like keys to locks of the cells. For example, for people are infected with the SARS virus, the first symptoms they show are cough or bad throat because the SARS virus has receptors that only match with the cells of lungs. Once it attaches to a cell, it reproduces to a great extent by getting access to a cell’s genetic material and hacking it to replicate itself.

So, all of the viral copies generated inside the cell can rupture the cell membrane and get out of the cell to invade other unsuspecting cells which then produce more copies and then so on and so forth. This is a lytic cycle. Another way other viruses spread is through the lysogenic cycle: when they don’t replicate inside the cell but rather let the cell replicate with its DNA and the DNA of the virus as well. However, sooner or later, the lysogenic cycle will trigger the lytic cycle which will do all that I mentioned above.
The virus’ action against the cell, or the immune response to infection, and both can lead to symptoms such as fevers, coughs and more serious symptoms like shortness of breath, skin rash, red eyes etc. While the virus’ action is self-explanatory, the immune response part is strange as you would expect the immune system would protect you however the immune system can be duped into attacking and killing infected cells and healthy cells which can cause severe damage.

 

Though, viral infections aren’t the only forms of infections. You can see all the various types of infectious diseases in the movie when the immune workers are doing their jobs. Bacteria and other micro-organisms like yeast can also infect the body.

Infection by Bacteria and other micro-organisms

Our body is in constant threat of thousands of attacks from bacteria every day. Unlike viruses, there is no debate about whether Bacteria are alive are not; they are and a bacterium can often be a single cell. Bacteria usually requires some kind of opening to enter the body, whether that be a cut on the skin, or through you nose, mouth, etc. At first, they only reproduce and use the resources of your body to twice their population every 20 minutes. However, when a certain amount of population is reached, they start to damage the environment around them.

Sometimes bacteria multiply so rapidly they crowd out host tissues and disrupt normal function. Sometimes they kill cells and tissues outright. Sometimes they make toxins that can paralyze, destroy cells' metabolic machinery, or ignite a massive immune reaction that is itself harmful to the body.

Not exactly as dangerous as viral infections, but still up there.

Immune Response

Our human body has a sturdy defense mechanism against these infectious agents. The first and the most obvious layer is our skin and that’s why you get a shot every time you scrape your knee in sports. Once an infectious agents passes through the skin, it is greeted by macrophages, your guard cells. Most of the time, they alone can fight off the attack by absorbing 100 intruders per units. Macrophages are a type of white blood cells like Osmosis Jones.

Until now, your immune system has demonstrated a non-specific response; meaning this response is for all pathogens. If the pathogen has not been exterminated yet, the body must move to specific responses. This part is called adaptive immunity which is the process of identifying an antigen (that is a part of a pathogen) and then exhibiting a cell mediated or humoral response.

The cell mediated response consists of the “Cytotoxic T cells” which kills the infectedcells. These bad boys are activated by either an infected cell which presents the antigen of a pathogen on its surface or by a macrophage presenting it on the surface joined by a “helper t cell”.

The latter consists of b cells (another type of white blood cell) which can create antibodies. Antibodies are proteins designed specifically for an antigen. They can bind to a specific antigen making it immobile, slowing its reproduction or signaling the macrophages mentioned above to come and absorb the pathogen.

Both of these process contain memory cells which is where the magic happens. These cells create a “memory” of the antigen they were exposed to and so these cells can activate b cells to make antibodies and activate Cytotoxic T cells which will hunt infected cells. This memory aspect is how immunity to a pathogen is developed. That is why injecting vaccines which stimulate this process is so effective.

Verdict

While in the movie, ozzy jones defeats the virus by simply throwing it out of the body; in real life, it’s different as the virus would have already created millions upon millions of copies at that point. Though, our bodies have a robust system designed to combat these pathogens which is more complicated than the movie lets on. Immunity is our greatest defense against infections and it is developed by exposure to the pathogen. This is why vaccines are so important and effective as they stimulate the parts of our immune system that make us immune to the original pathogen. We are exposed to thousands of infections every day and yet don’t even feel a thing most of the time. That is due to our incredible immune system. Be thankful for it!

References

https://www.jacionline.org/article/S0091-6749(05)01476-4/fulltext

Tosi M.
Innate immune responses to infection.

J Allergy Clin Immunol. 2005; 116: 241-249

Wessner, D. R. (2010) The Origins of Viruses. Nature Education 3(9):37

https://www.youtube.com/watch?v=FnPOuK9RHH0

https://www.youtube.com/watch?v=zQGOcOUBi6s

https://www.youtube.com/watch?v=fSEFXl2XQpc&t=1s

https://www.youtube.com/watch?v=jEveVtZmPu0