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Let’s Talk Science and the Royal Society of Canada have partnered to provide Globe and Mail readers with relevant coverage about issues that affect us all – from education to the impact of leading-edge scientific discoveries.

Fatima Tokhmafshan is a science communicator, genetics researcher, and medical student. She is the Director of Community and Patient Outreach and Engagement at CoVaRR-Net (Coronavirus Variants Rapid Response Network).

Every day we encounter millions of microscopic organisms that can cause serious damage if it weren’t for our brilliant immune cells. How do they do it? By working together like your school staff. So, let’s meet just a few of the characters that run your body’s School of Immunity and have perfected learning and teaching the art of defence over millions of years of evolution.

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Neutrophils (pronounced NOO-truh-fil) are like the maintenance staff, always present at the first sign of trouble. Neutrophils vanquish microbes by swallowing them up, bathing them with toxins, or sacrificing themselves by rupturing and spilling their contents out – all preventing the spread of infection. The result is pus - a yucky-looking substance that contains many dead neutrophils that have sacrificed themselves to protect you! But some microbes are just too strong for neutrophils, that’s when other types of cells, like macrophages, try to help.

Macrophages (pronounced mak-row-fayj) like the hardworking school custodians are constantly cleaning our bodies by snarfing down microbes and dead cells. They then share pieces of stuff they have eaten with dendritic cells so they can sound the alarm and recruit other helper cells. But macrophages too can be bypassed by some microbes. This usually spells disaster because if macrophages can’t do their job, neither can dendritic cells.

Dendritic cells (pronounced den-dri-tuhk) like school guidance counsellors are constantly analyzing pieces given to them by macrophages and informing B and T cells about the latest threat around. But with some sneaky microbes, dendritic cells don’t get to sound the alarm until it’s too late!

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Mast cells like a school’s athletic director are focused on keeping other immune components in shape and motivated. But sometimes they make other cells too hyped up and cause allergic reactions. Mast cells work closely with dendritic cells, training them to reach maturity and fulfill their role. SARS-CoV-2 (the virus that causes COVID-19), is one virus that can overexcite our mast cells, causing our bodies to show allergy-like reactions and even interfere with mast cells’ ability to effectively coordinate the activities of other immune cells.

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B cells like art teachers are creative. They produce millions of different molecules known as antibodies to protect us against microbes. B cells can remember the information dendritic cells have given them, though occasionally they need reminders to produce more specific and effective antibodies. Antibody production relies on the chain of information passed on to B cells, which means there is a delay between exposure to microbes and antibody production. This is one reason we could get very sick after being exposed for the first time to a fast-acting microbe like SARS-CoV-2 and why it takes a couple of weeks for us to build immunity after vaccination.

Antibodies like students are the product of the school staff’s attentive teamwork. Antibodies resemble a lock with grooves customized to fit specific parts of microbes (antigens). Antibodies float in blood, circulating the entire body looking for their microbe match and then lock it in place, preventing it from making us sick. However, keeping up a massive production of antibodies for long periods is not very cost-effective for our bodies—so antibody levels rise and fall as threats are identified.

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T cells like a school principal, are always watching, learning, coordinating, and directing. T cells are the most sophisticated and effective defence against diseases, from infection to cancers. But if these talented multitaskers and coordinators of immunity detect a microbe that either has escaped or overpowered other immune cells, they go into a frenzy and release a lot of chemicals to get rid of the infection. This strong response is like a storm, causing significant damage to everything in its path, including our own cells. This is one reason some people need hospitalization for COVID-19.

Wouldn’t it be great if there were a way to support our immune cells, helping them learn what to watch out for? Just as schools run fire drills as part of their emergency preparedness, we can help our immune cells prepare for emergencies caused by sneaky microbes with the help of vaccines. A vaccine contains a very small amount of a harmless microbe component (antigen). Vaccines teach B, and T cells to build memory about the microbe and identify and neutralize it once we get exposed to it.

Infection might also help our B and T cells build memory, but infection and sickness are not natural states and come with a significant risk of damage depending on whether our immune cells over or underreact. Wanting to build immunity from infection is like training for fire emergencies by setting an actual fire—sure, this could teach you a lot about fires, or it could get out of control and cause serious damage to those around. The strength of infection-generated immunity depends on how much we were exposed to the infectious microbe. Imagine if your teacher gave different amounts of study material to you and your friends, some of your friends might get many pages and others might get just a few and therefore not have the same opportunity to prepare for the exam.

Giving the same amount of study material to all students is the best way of increasing the number of students who pass the exam. And that is precisely what vaccines do, they offer everyone’s immune cells the opportunity to learn from the same amount of microbial components that have been modified to be harmless. Of course, there will always be differences in how much immunity each person generates, but with vaccines, we significantly increased the chance of most people generating a good and uniform level of protection.

So, what better way to thank and support our smart and hardworking immune cells than by giving them the opportunity to safely learn about new microbes and do what they were born to do: to protect us?

Give yourselves and your super immune cells the best shot—give them vaccines!

Learn more about vaccines through Let’s Talk Science.