The Warrior Within: Exploring Your Immune System
Your body has a superpower called the immune system!
Imagine your body as a fortress, constantly under siege by invisible invaders. Within this fortress lies a hidden superpower: your immune system.
Picture this: In 2020, the entire world watched as a real-time science experiment unfolded. Every day, people battled viruses like the common cold and the flu. These skirmishes were a stark reminder of how our bodies protect us.
Your immune system is nothing short of extraordinary. The unsung hero defends your body against harmful viruses and pathogens, day in and day out. Think of it as a vigilant knight, always ready to act. This powerful defender is divided into two forces: innate immunity, the first line of defense, and adaptive immunity, the specialized troops that remember and target specific invaders.
Join me as we delve into the fascinating world of your immune system, the body's tireless guardian.
Innate Immunity
The innate immune system is the body's first defense against pathogens entering the body. When your body is introduced to an unfamiliar pathogen (a bacteria, virus, or fungi), an alarm goes off, and the body immediately begins fighting foreign antigens. Antigens are substances that initiate an immune response. There are two types of antigens: foreign and autoantigens. Autoantigens originate within our bodies, while foreign antigens come from external sources.
The actions of the innate immune system begin with pattern-recognition receptors (PRRs), which mediate the innate immune system. Once a pathogen enters the body, PRRs detect pathogen-associated molecular patterns (PAMPs). The detection of PAMPs initiates an inflammatory response and activates other innate immune defenses.
“ Think of PRRs as a security scanner and PAMPs as a suspicious pattern that leads to extra security forces coming to the area.”
The chart below shows specific cells that play a key role in the innate immune system’s defense against infections. Each cell has a different function that protects and defends our bodies from pathogens.
Although the innate immune system has an excellent response, it is a nonspecific response. This means that the body only identifies the fact that there is a foreign substance in the body. The innate immune system cannot identify the specific virus present. The nonspecific response of the innate immune system helps prevent the disease from spreading further until the adaptive immune system activates. Dendritic cells are the innate immune cells activating the adaptive immune system.
Adaptive Immunity
The adaptive immune system is your body's second and strongest line of defense. T and B cells are responsible for carrying out most of the activities in the adaptive immune system. Unlike innate immunity, adaptive immunity has a slow and specific response. Adaptive immunity is acquired over your lifetime because the adaptive immune system has a “memory.” You’re probably thinking - a memory? Well, Yes! Let’s talk about how adaptive immunity works…
B cells
You may have heard the word antibodies in the news many times over the last year. Antibodies are the proteins that are produced in the presence of antigens. B cells are responsible for producing specific antibodies against viral antigens.
“Think of antibodies as the Avengers. The Avengers only arrive when there are specific villains present…"
When the B cells bind to the viral antigen, a cascade of events is triggered, eliminating the pathogens set forth in our bodies. “Imagine knocking down the first domino that leads to the rest of them falling.”
One of the events triggered is the expansion of B cells. Long-lived plasma cells and B cell memory cells are produced during B cell expansion. These two cells are essential because they retain a memory of the viral antigens. Upon reinfection, these cells will neutralize or produce specific antibodies to eliminate the virus quickly!
This stimulation of immune memory is one of the critical components of developing a vaccine. Triggering that adaptive immune response plays a vital role in the development of immunity. The CDC defines immunity as the body’s ability to neutralize or destroy a virus with specific antibodies.
If exposed to the same antigen again, your immune system could fight off antigens faster because your adaptive immune system will produce specific antibodies to protect you from reinfection.
T cells
T cells are the second type of cells produced by the adaptive immune system. You can think of T cells as soldiers. There are two significant types of T cells: CD4+ helper and CD8+. Okay, this might sound super complicated, so let’s simplify it.
“Think of CD4+ helper cells as the medics on a battlefield.” These CD4+ helper cells are responsible for helping B cells expand and activate CD8+ cells. “ You can imagine CD8+ cells as the battlefield soldiers that attack, kill the pathogen, or signal other cells to attack.”Virus-specific CD8+ cells are produced during the first week of infection. CD8+ cells are abundant during the first two weeks after you are infected with a virus.
This is a response to your body killing the virus. The CD8+ cells present during this process are short-lived because most disappear a few days after your body has terminated the virus. However, a few CD8+ cells remain, becoming CD8+ memory cells that remain in your body for a lifetime!
Key Takeaways
So, the immune system is complicated but beautiful! Listed below are the key takes of this blog!
There are two immune systems with different functions: the innate immune system and the adaptive immune system.
The innate immune system is the body’s first, fastest, nonspecific line of defense against pathogens.
Innate immune cells activate the adaptive immune cells.
The adaptive immune system produces specific antibodies to fight the foreign invaders in our bodies.
A memory of the viral antibody is developed in the adaptive immune system.
The adaptive immune system plays a key role in developing long-term immunity.
Definitions
Antibodies: a protective protein the immune system produces in response to the presence of a foreign substance called an antigen.
Antigens: a substance that is capable of stimulating an immune response.
Pathogen: virus, bacteria, or fungi that cause disease.
Pattern-recognition receptors (PRRs): receptors that recognize pathogens.
Pathogen-associated molecular patterns (PAMPs): structures produced by pathogens.
Immunity: the body’s ability to neutralize or destroy a virus with specific antibodies.
References
B Cells. (2020). British Society for Immunology. https://www.immunology.org/public-information/bitesized-immunology/cells/b-cells
Blanchard, N., Salvioni, A., & Robey, E. (2020). Adaptive Immunity. Toxoplasma Gondii, 57–68. https://doi.org/10.1016/B978-0-12-815041-2.00026-8
Cells of the Innate and Adaptive Immune System. (n.d.). [Chart]. https://www.novusbio.com/research-areas/immunology/adaptive-immunity
John Wherry, E., & Masopust, D. (2016). Adaptive Immunity Neutralizing, Eliminating and Remembering for the Next Time. Viral Pathogenesis, 57–68. https://doi.org/10.1016/B978-0-12-800964-2.00005-7
Purtha, W. E., Tedder, T. F., Johnson, S., Bhattacharya, D., & Diamond, M. S. (2011). Memory B cells, but not long-lived plasma cells, possess antigen specificities for viral escape mutant. Journal of Experimental Medicine, 2599–2606. https://doi.org/10.1084/jem.20110740
MacDonald, A. (2017). Antigen vs Antibody – What Are the Differences? Technology Networks. https://www.technologynetworks.com/immunology/articles/antigen-vs-antibody-what-are-the-differences-293550
Molnar, C. (2015, May 14). 12.2 Innate Immunity – Concepts of Biology – 1st Canadian Edition. Pressbooks. https://opentextbc.ca/biology/chapter/12-2-innate-immunity/
Silva-Gomes, S., Decout, A., & Nigou, J. (2014). Pathogen-Associated Molecular Patterns (PAMPs). Encyclopedia of Inflammatory Diseases, 1–16. https://doi.org/10.1007/978-3-0348-0620-6_35-1
Types of Immunity to a Disease | Vaccines and Immunizations | CDC. (2017). CDC. https://www.cdc.gov/vaccines/vac-gen/immunity-types.htm
