This Is How Your Body Builds Immunity

Vaccines are possibly the greatest thing that
humans ever created. Not just in the realm of medicine, but like all of human creation.
Space travel is awesome. Agricultural revolution? For the most part, pretty sweet. The entirety of YouTube? Up there, but maybe not as lifesaving as vaccination. Vaccinations has its roots in variolation,
a technique developed by Asian physicians prior to the 1700s. They would take dust
from someone’s smallpox scab and blow it into their patient’s nose — the patient
would experience a weaker version of smallpox, but then they’d be immune to it for life. Variolation
was far from perfect, and just sounds gross, but when the alternative is contracting a
potentially fatal version of smallpox, it was a good first step. In the hundreds of
years since, doctors have made huge advances in vaccination technology like Edward Jenner’s
famous smallpox vaccine made from cowpox virus, or Louis Pasteur’s vaccines against rabies
and anthrax. But here’s the thing — all of these revolutionary concepts in science
came before we knew how our immune system worked on a cellular level. So today, we’re
going to go through the story of early immunology to learn how they figured out the cells of
the immune system. Around the same time as Pasteur, a Russian researcher named Elie Metchnikoff
was studying starfish larvae and noticed that certain cells would engulf foreign objects.
He called these cells phagocytes, which meant devouring cells. This seemed like a viable
explanation for how immunity worked — our cellular defenses gobbled up potential threats.
But during the development of the diphtheria vaccine, another idea was put forward. German
scientist Paul Ehrlich hypothesized that there was some kind of anti-toxin floating in the
blood that would confer immunity. These would later become known as antibodies. So by the
end of the 19th century, scientists knew that germs caused disease, that substances in the
blood could confer immunity, and that cells could swallow up pathogens. But we still had
some big questions to answer. Specifically, there were two schools of thought regarding how immunity works. On one team were the “cellularists” who thought that free floating phagocytes
were more important to immunity than antibodies. This became known as cellular immunity. On the
other team were the “humoralists” who believed in humoral immunity. To them, clearly
something dissolved in the blood had to mediate immunity. So to start with, your body has
an immune system that keeps you safe from pathogens, anything that causes disease like
a bacteria, parasite, or virus. Those researchers at the end of the nineteenth and start of
the twentieth century were debating two types of immunity that we now know are both present
in our bodies. From 1900 to the 1940s, it seemed like the humoralists had a better case.
Experiment after experiment showed that antibodies conferred immunity. Plus, scientists were
zeroing in on how antigens hook up to antibodies and antibodies’ structure. But the importance
of the humoral theory was challenged during a major experiment in 1942 by our old friend
Karl Landsteiner, that dude that discovered ABO blood types, and his colleague Merrill
Chase. They took one set of guinea pigs and gave them the tuberculosis bacteria, which
meant they would build antibodies and thus immunity to TB. Then they injected the blood
serum with TB antibodies into naive guinea pigs, or non-immunized guinea pigs, and later
exposed them to the TB antigen. But the immunity transfer didn’t work. So maybe antibodies
weren’t the only thing conferring immunity? Chase next tried to immunize his guinea pigs
with a new solution, which accidentally contained lymphocytes, white blood cells that play a
huge role in our immunity. When the research team looked under the microscope, they saw
these immune cells at work, which strengthened the cellular immunity theory. We had way
more questions though. Like if there are millions and millions of types of pathogens out there,
how does our immune system make antibodies for all of them? There was no way millions
of species of cells were built into our bodies for millions of antigens, so we must have
to manufacture antibodies after being exposed to the pathogen. This gave rise to something
in the late 50s called clonal selection theory, which, as the name suggests, implies clones,
or copies of cells. First, humans along with other animals have immune cells called lymphocytes.
They’re a thing that exist and have a name by this point. Lymphocytes respond to antigens
according to receptors on the lymphocyte’s surface. When that lymphocyte gets in contact
with its appropriate antigen, it will proliferate, or clone itself. From there, the clones will
either secrete antibodies or recruit more cells to respond to the pathogen. But that
still didn’t show us how lymphocytes recognize antigens themselves. Then in the early 1960s,
scientists started paying more attention to an organ called the thymus, an organ in the
lymphatic system which until then, wasn’t completely understood. So a scientist named
Jacques Miller removed the thymus from infant mice and noticed that the mice developed more
severe infections and mounted weaker antibody responses. So that seemed like some easy math.
Take out the thymus and the immune system weakens. But how exactly the thymus supported
immunity was still a mystery. By this point, scientists knew that cells in the bone marrow
could make hematopoietic stem cells, those types of cells that can become any type of
blood cell. So maybe lymphocytes started in bone marrow and mature in the thymus. Enter
James Gowans, who traced lymphocytes all around the body and found that they went from the
blood into lymphatic circulation, then into lymph nodes, and back into the bloodstream. This
gave us the idea that the thymus manufactured lymphocytes, which then traveled through circulation,
eventually coming to secondary lymphoid organs like lymph nodes. Now that we knew where lymphocytes
came from, we could tie that back to the old clonal selection theory. They got the idea
that naive lymphocytes, or lymphocytes that hadn’t been activated by an antigen yet,
grew up in the thymus. Then when they were excreted and made it to the
lymph nodes, they would differentiate into fully functioning, antibody-producing plasma
cells depending on which antigen they encountered. So they were born in the bone marrow but grew
up in the thymus. These thymus derived cells became known as T cells. Around the same time,
separate scientists saw that lab chickens developed an impaired antibody responsiveness
when they removed their bursa of Fabricius, a bird-specific lymphatic organ found near
their little chicken butts. That complicated our nice, tidy definition a bit because that
meant that there might be two types of lymphocytes. Through a series of experiments on chicken
embryos, scientists found that different lineages of lymphocytes developed in the thymus compared
to the chicken’s bursa. These became known as bursa derived cells, or B-cells, which
mediated humoral immunity. Thus, the two superstar cells of the adaptive immune system got their
names. Fun fact, humans do have structures called synovial bursa, but they’re more
cushioning for our joints — so they’re different from the bird version. That raises
another question though. Humans aren’t birds. Like not even a little bit. So we don’t
have the organ that produces B cells that birds do. So where do humans make B cells,
and how does the whole immune response work with all these moving pieces? As it turns
out, B cells both form and mature in the bone marrow itself. They only start to differentiate
once an antigen hooks up to any of the receptors on its surface. By now we’re in the 1970s,
and we still had a few things to figure out, like how the T cells don’t just self destruct
and kill our own cells. See, bacteria infect our bodies differently than viruses. Bacteria
will invade our bodies somehow, then reproduce by splitting apart into two cells. But viruses
get directly into the host’s living cells, then use their host’s cellular machinery
to reproduce, and eventually burst out of those cells to infect more cells and keep
the process going. So to keep that virus from hijacking more of your cells, sometimes your
immune system needs to kill off your own cells. During an experiment published in 1974, researchers
saw how our immune systems could differentiate our infected cells from other cells. In it,
they gave a virus to a bunch of lab mice, and swapped T cells from one mouse to another. The
T cells did their normal job as expected. They’d destroy cells infected with viruses
but, unexpectedly, only if the infected cell came from the same strain of mice as the T
cell. If a T cell detected that a random cell was infected with a virus, but it was
from some other mouse, it wouldn’t destroy it. Basically, T cells showed that they would
only help cells from their same family. This would become known as self-nonself discrimination.
This was a big development because it showed that T cells only destroyed foreign cells
if they presented an antigen and presented a molecule that identified it as a “self”
cell. That identifying molecule was major histocompatibility complex, or MHC for short,
a molecule that presents the antigen-of-interest to different T cells. Then in 1978, scientists
identified the dendritic cell, a phagocytic cell that eats up pathogens and presents its
antigen to the other cells, helping to eventually grant immunity to that pathogen. That made
it an APC, or antigen-presenting cell. I have slayed this E coli for you! Behold! Feast
thine eyes upon its carcass! One of the most recent discoveries in the story of B and T
cells shed some light on how these two types of immune cells work together. In order for
our cells to remember that pathogen, the APC will present an antigen to one type of T cell
so it can destroy the pathogen, while another type of T cell will share that antigen with
B cells, which then make antibodies for it. That development would let us understand how
those early vaccines at the start of the twentieth century worked. The vaccine itself is a weakened
or imitation pathogen that we administer to people without immunity to that pathogen. Their
bodies respond first by attacking the pathogen, but then build up a reservoir of memory T
cells and antibodies from B cells to attack that pathogen in the future. After all those
years of not knowing how vaccines were saving lives, we finally learned how. Next time,
we’ll learn about a major source of those B and T cells, the lymphatic system. I hoped
you liked this episode of Seeker Human, I always love these history based episodes.
They’re so fun to write. I’m Patrick Kelly and thanks for watching.


  1. … then we still had this problem… 5 minutes later… some parts of the animal was removed and they were infected with different disease and observed

  2. Listen carefully- the science was new and unfolding in the 1940’s and 1970’s. That wasn’t long ago! We are so lucky to be living when we know so much more about disease, but we are still learning and discovering new ways our bodies work today. I find it fascinating how fast we have moved forward in medical science. Great episode! Love the brief history lesson.

  3. Not mine🙅‍♀️ Thanks to CVID/Primary Immunodeficiency.. don't produce enough T-cells of which don't properly activate B-cell maturation. Although wkly subQ immunoglobulin therapy ups the IgG, ImmunoglobulinA deficiency is incurable & makes for being highly prone to contract & develop viral & bacterial infections.. but I get told by fam, support worker to go out, practice self-distancing & hope for the best🙄🤦‍♀️

  4. May I ask a question, we used Manuka in the hospital to treat wounds, the results were positively outstanding. Do you think honey will help folk fight this virus? Be safe and well. 💙

  5. If you figure out the resonant frequencies of all viruses, bacteria and parasites, you can kill it like how sound waves shatter glass when frequency matches the resonant spot of glass.
    “If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.” ― Nikola Tesla.

  6. I was wondering why would all these Guinea pigs allow scientists to experiment on them. Turns out they're Naive

  7. Another great example of how we were created. Soooo many moving parts working in unison to try to keep the body healthy.

  8. Vaccine are just painful to get and after they attak our body with lower harmful cell than it can actually be then our immune respone to those and protect us as it is our protector and make a memory cell of it. From where that weak bacteria(or virus) they got to inject??? And vaccine protect from bacteria or virus?????

  9. Question. Which if any of the following statements are true enough to be helpful to my understanding?

    "if/when I am 'infected' with the corona virus, and develop dry cough and fever symptoms, I will then (after approx 14 days from infection?) be immune to that strain of the virus"

    "if/when I am 'infected' with the corona virus, and remain asymptomatic, I will then (after approx 14 days from infection?) be immune to that strain of the virus"

  10. The first thing a person needs do to maintain a healthy immune system is to not sit on Joe Biden's roach laden, hairy legged, child lotioned lap as was suggested in the commercial at the beginning of the video. Gotta git our priorities straight…

  11. Interesting fact (etimology):
    The term Vacination comes from the usage of virolation using infected cows in Australia when it was a prison of the British empire. COW in lattin is VACCI, hence the name.

  12. This is all very informitive, but I know for a fact that we will never be immune to the coronavirus. We're all doomed!

  13. CV was bioengineered by diabolical chineese as a weapon. Now that they have done their little experiment, they will modify it or develop a more deadly, more contagious version. Since it is manufactured, eradication is impossible as they will just keep releasing it covertly forever. Try fighting that. Barring nuking them to oblivion, there is no solution.

  14. Dude why is everybody hiding the fact that Vaccines were created by Indians. Its not Asian it's India's most ancient book of medicine Ayurveda!!!

  15. What does the CDC/NIH say about getting a flu vaccine and it's relation to getting other respiratory issues?

  16. Hi Seekers, thanks for watching! For more on viruses, check out our explainer on COVID-19 here:

  17. This system is just perfect! It shows the need for a mighty, willful, knowing existence that makes those things possible and maintains them every moment. I'm NOT saying there should be only a designer, there should be a Maintainer that chooses the reality to be the way we observe it is every moment and orders the material in the universe to be in order.

  18. Does it not bother ANYONE else that he says "pacifically" instead of "specifically" right around 1:55? I rewound the video a million times to listen to him with my eyes closed and its driving me nuts because it LOOKS like he's say specifically but he's noooooot lol wow this bothers me way more than it should.

  19. Did the Chinese government know how long the non symptomatic contagion period was when Chinese students and workers returned to their overseas homes? Did those leaders know they were releasing a million Typhoid Mary's onto the world?

  20. You were designed. Everything, right down to the cellular level was all designed. You have to be ignorant to believe all this evolved into existence.

  21. For those who think we should do medical research and less physics or space science: Much of our current advanced knowledge shared in this video was only possible because of what nuclear physicist learned, and much of that was from the cross fertilization of astronomy and quantum mechanics and much of that was affected from what we learned in many of those lab experiments on the space stations…ultimately we may discover all knowledge at some point becomes interrelated. Stopping any research is to stymie all research.

  22. So basically the only way you can build up immunity is by being exposed, only then will your body be able to produce the necessary antibodies.

    Once a vaccine is created for coronavirus, you will literally be injected with a dampened down version of the virus itself.

  23. anyone can find me how to type the cell he is talking about at 6:55–7:00, i want to research that for my disease.

  24. • But where does the body keep the information for pathogens? Surely it can't keep lots of copies just hanging around all the time, even when not sick with that disease. Is there some sort of "database" where it keeps the information for future use while not cluttering up the system with antigens for every single disease you've ever been infected with? 🤔
    • Well, you did it, you finally figured out a way to wear the gauntlets on camera, even if it was a bit contrived. 😀

  25. Sanitation and food safety standards have saved more people than vaccines. Our janitors need a lot more credit.

  26. How the hell is the Agricultural Revolution "for the most part, pretty sweet"?? You're basically saying overpopulation and the switch from sustainability to unsustainability was a good thing.

  27. Note that this whole history explanation of vaccination shows no reason for the inclusion of hundreds of toxic chemicals including Mercury and aluminum which immediately destroy brain cells, or why all vaccines should start out using cancer cell lines. Vaccines as they are designed and produced by the so-called medical community are the worst most horrific inventions in human history they are being used to shorten life spans destroy brains, induce debilitating diseases of many types and in many cases to cause outright death nearly immediately upon injection. But then this entire history lesson doesn't seem to think any of that is important.

  28. Thank you for this. I studied immunology in the research lab where Jacques Miller did his great work. It was incredibly hard for me at the time to understand how all the moving pieces work and you've done a very credible job of explaning that fit everyone. Btw Pasteur remains my all time hero. Not just for principles of vaccination and disease but for incredible other discoveries such as left and right handed molecules. Maybe a segment on him with a recap that he said "chance favours the prepared mind". We must keep educating and our minds receptive and prepared to change our discard beliefs when they are shown to be false however uncomfortable that may be. Thanks again!

  29. My god, this theory has been repudiated many times across decades. Something tells me Seeker is on the take of commercial, for-profit interests like Big Pharma. Even the most cursory examination of the past 220-225 years [human population hit 1 billion between 1795-1800], as well as the prior 500 years, show that vaccinations are not responsible for humanity's surge and survival success. 

    Instead, it's all about a more accurate and robust immune system from better lifestyles, improved sanitation, improved hygiene, fresher foods, superior nutrition and so forth. Seeker is making an argument that died a long time ago. And now that we know so much about the microbiota / microbiome and it's role in training and helping sustain our immune system, there's no excuse for this rollover to Big Pharma. 

    And if you've seen how vaccines are made, you'd never think about getting one! Primitive, imprudent and a big gamble.

  30. Please can we cut that techno crap in the background? I love electronic music but that drivel doesn't really go with this video. It's just annoying, too loud, and competing too much with the narration.

  31. So you just used science to prove that vaccines are not beneficial.
    Because it's preparing for a weakened virus that it will never encounter in the real world.

  32. So if one get the coronavirus and recovered from it does this person develop antibodies or this is not confirmed…

  33. Can we stop for a moment and realize how important it is to do animal experiments. Many people are against it but it’s crucial for our understanding and well being.

  34. You can be outright immune to a virus without any exposure, you just have to not have the protein receptors needed for the virus to gain access to the cells.

  35. Bat sucking chicken blood sold in China meat market , that may have been what started the virus …? that's a question if you didn't know ? And don't call me baby and i won't call you daddy ……

  36. now they add all sort of bad things like a form of mercury or what they call adjuvants which are very bad for humans

  37. sure ::: i stopped getting sick all the time… 20 years ago ::: when i stopped injecting vaccines… 🙂 … i have never got ill ever since… 😀 … and you ::: should stop deceiving your self and your viewers… o.O?… please.

  38. Hey I'm and an Exercise Physiologist in Australia, we know so much about the body in our studies, great to see you presenting this!

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