Immunology

Chances are you had a cold over the winter (maybe even the flu!) or you’re currently experiencing seasonal allergies. Whether it’s a cold or allergies, the immune system is at work. 

Immunology is the study of the immune system. We can think of the immune system as the body’s police. Much like police, the immune system is constantly searching for invaders (bacteria, infections, viruses), rule breakers (allergens) and fugitives (cancer cells). The immune system searches and finds these “bad guys,” and on a good day, our immune system gets rid of them before we even know they’re there. However, in some cases the immune system takes a little longer to clear out the bad guys and you do get sick. And then other times, the immune system is completely unable to rid your body of the bad guys, like when you’re diagnosed with cancer. Today, we are going to go over the different parts of the immune system, how some of the “bad guys” are able to avoid the “police” and we’re even going to touch on the controversial topic of vaccines.

The immune system is made up of two main groups, the innate immune system and the adaptive immune system. These two systems work individually but have some overlapping pieces. The innate immune system can be thought of as the sheriff’s department. Much like the sheriff’s department, the innate immune system is the first to react to the problem. Just like the sheriff’s department doesn’t have a lot of resources, neither does the innate immune system. 

The adaptive immune system is much more powerful than the innate immune system. For this reason, we can think of adaptive immunity as the FBI. The FBI isn’t going to react to a small theft committed by a minor, but it will react to a fugitive that has been on the run for years. The FBI comes into play when the sheriff’s department can’t stop the bad guys, likewise, the adaptive immune system reacts when the innate immune system can’t fully protect your body. 

You may be asking, if the adaptive immune system is so much stronger, why do we even need the innate immune system? Well, let’s think about the FBI again. There aren’t enough agents to have a station in every single little city and county across the nation, that’s where the sheriff’s departments come in. Likewise, the innate immune system is constantly surveying your body for bad guys, and when it identifies an issue that it can’t control, the adaptive immune system, or FBI, gets notified. Much like the FBI may take a few days to prepare, plan and respond to these issues, the adaptive immune system also has a latent phase and normally responds within 3-7 days.    

There are many key players in both the innate immune system and the adaptive immune system. These key players are different types of cells, proteins and other other substances, each playing a crucial role. 

Key players in the innate immune system are listed below:

PlayerFunctionOther info/ Examples
Physical Barriers (skin, eyelashes, etc)The first defense mechanism to prevent viruses, bacteria and other pathogens from entering your body
Defense Mechanisms (secretions, mucous, gastric acid)Once a pathogen enters the body, oftentimes bodily secretions can eliminate it. Think of the low pH of stomach (gastric) acid. Some pathogens that have been ingested can’t handle this low pH and die as a result.
Mast cellsHelp initiate immediate hypersensitivity reactions to invading pathogensReleases a chemical called histamine which helps other immune cells enter into the tissue and fight the pathogen. Responsible for allergic responses.  
Granulocytes (Neutrophils, Basophils and Eosinophils)A type of white blood cell that helps fight infection by secreting proteins that are able to attack the pathogen
Monocytes (Macrophages & Dendritic Cells)1) Uptake and destroy microbes (phagocytosis)2) Gives T cells and B cells information on invading pathogens to prepare them (antigen presentation) 3) Notifies other immune cells by releasing proteins (cytokine production)
Natural Killer (NK) CellsActivated by macrophages via cytokines (signalling proteins), contain and fight infectionsSimilar to cytotoxic T cells of the adaptive immune system

Key players in the adaptive immune system are listed below:

PlayerFunctionOther info
AntigenA foreign substance which induces an immune responseMacrophages and dendritic cells can present these foreign substances to T cells to initiate an adaptive immune response (antigen presentation)
Antigen Presenting Cells (APC)Cells that present antigens to T cellsDendritic cells and macrophages, B cells can also function as APC
T cellsWhite blood cells classified by two main groups:1) CD4 – “Helper” T cells2) CD8 – “Cytotoxic” T cellsCD4 T cells can activate B cells and releases cytokines (rings alarm to alert further immune response)CD8 T cells kill infected cells 
B CellsAntibody making cells
AntibodiesAntibodies are proteins that are used to tag pathogens, signaling for cytotoxic T cells and other cells to attackProduced by B cells 
Memory T cellsT cells that stick around a lot longer and “remember” the pathogen that the cell originally fought againstIf the pathogen reemerges later on, the memory T cell can act quicker and kill the pathogen because it is already able to recognize the antigen
Memory B CellsB cells that stick around a lot longer and “remember” the pathogen that the cell originally fought againstIf the pathogen reemerges later on, the memory B cell can act quicker and kill the pathogen because it is already able to recognize the antigen
CytokinesProteins released by various immune cellsCan activate signaling cascades, promote inflammation, activate other immune cells, etc.

You may have noticed that some of the key players in the innate immune system carry over into the adaptive immune system.This helps increase cooperation between the two groups to effectively catch the pathogen. This Venn diagram shows where the overlap occurs:

The sheriff’s department and FBI never like to be surprised, to avoid this they use informants who tell the secrets of the invader, so the key players listed above are prepared for an attack. Likewise, the innate and adaptive immune systems work much better if they already have information on the virus/ bacteria, and they get this information from vaccines. There are multiple types of vaccines. They can include dead or attenuated (weakened) viruses and bacteria or just a particular viral or bacterial protein. In the same way, vaccines tell the adaptive immune system what parts of the bacteria or virus it should target. Once a vaccine is given, memory T cells and memory B cells are created for that important part of the pathogen. These cells flow through the body, ready to initiate an immune response if they ever come into contact with the real pathogen. Vaccines have led to the eradication of smallpox, and we are close to eradicating other diseases like polio, measles, mumps, rubella and more. 

Not only do vaccines help protect against viruses and bacterial infections, vaccines have also helped to significantly decrease the incidences of certain cancers, one example being cervical cancer. Gardasil (also called Cervarix) is a series of vaccines against the Human Papilloma Virus (HPV). While the vaccine itself informs the body of an invasive virus, this virus actually has the potential to cause cervical cancer (check back for all things cancer next week)! 

While some vaccines are associated with mild side effects, these side effects are much more manageable than any of the above listed diseases. Further, there are no vaccines or vaccine ingredients that have been scientifically linked to autism. Given our current global situation, hopefully everyone is becoming aware of the importance of vaccines. As the Coronavirus has turned the world upside down, can you imagine if “anti-vaxxers” allowed for the reemergence of smallpox or measles? Vaccines are a way to boost your immune system and protect you, your friends and your family from serious illness. GET VACCINATED! 

In conclusion, the study of the immune system is critical for many diseases. Currently, the most pressing of these would be treating/ preventing and developing vaccines for the Coronavirus; however, immunology is a broad topic encompassing cancer, rheumatoid arthritis, lupus, asthma, type 1 diabetes and so much more. 

Thanks for reading and make sure to check back next week for the launch of our CANCER (part 1) introductory post! In the meantime, let us know if you have any questions, comments or feedback and don’t forget to follow/ like us!

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Written by Annah & Megan
Illustrated by Rhea

Disclaimer: We are not medical professions and the above information is not meant to serve as diagnostic factors or medical advice. Further, the opinions in this post are our opinions and in no way reflect the opinions of our mentors or the Medical University of South Carolina.

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