1/M
For months, COVID-19 contrarians spread misinformation about the immune system and COVID-19.
So I'll combine some rebuttal points I've made elsewhere, with a focus on T cells.
For months, COVID-19 contrarians spread misinformation about the immune system and COVID-19.
So I'll combine some rebuttal points I've made elsewhere, with a focus on T cells.
https://twitter.com/AtomsksSanakan/status/1293374331519733762
https://twitter.com/AtomsksSanakan/status/1278588411629182976
https://twitter.com/AtomsksSanakan/status/1289556736320221185
https://twitter.com/AtomsksSanakan/status/1293424018071195648
2/M
An important concept here is 'herd immunity'.
In simplified terms:
The 'herd immunity threshold' is the number of people who need to be immune to infection, in order for 'infections per unit time' to stop increasing, at baseline.
medium.com/@silentn2040/t…
An important concept here is 'herd immunity'.
In simplified terms:
The 'herd immunity threshold' is the number of people who need to be immune to infection, in order for 'infections per unit time' to stop increasing, at baseline.
medium.com/@silentn2040/t…
3/M
So for the graph below:
y-axis = # of new infections per day
x-axis = time
This is under 'baseline' conditions; i.e. people don't change their behavior in response to infection, + no further public health interventions (ex: lockdown).
At x = 10, the threshold was reached.
So for the graph below:
y-axis = # of new infections per day
x-axis = time
This is under 'baseline' conditions; i.e. people don't change their behavior in response to infection, + no further public health interventions (ex: lockdown).
At x = 10, the threshold was reached.
4/M
So why would herd immunity matter to you?
Well, once the herd immunity threshold (HIT) is reached, you and everyone else can go back to *living as you did before the viral pandemic, without worrying about infections per day increasing.*
medium.com/@silentn2040/t…
So why would herd immunity matter to you?
Well, once the herd immunity threshold (HIT) is reached, you and everyone else can go back to *living as you did before the viral pandemic, without worrying about infections per day increasing.*
medium.com/@silentn2040/t…
5/M
So herd immunity sounds nice.
Unfortunately, many politically-motivated non-experts misrepresented it, since they view it as a way to dodge policies they dislike, such as lockdowns.
So herd immunity sounds nice.
Unfortunately, many politically-motivated non-experts misrepresented it, since they view it as a way to dodge policies they dislike, such as lockdowns.
https://twitter.com/curryja/status/1259513058575003651
6/M
Many non-expert contrarians assume that if infections per day (or hospitilzations per day, or COVID-19 deaths per day, or...) decrease, then that automatically means HIT was reached.
The contrarians typically apply this to Sweden or New York City.
judithcurry.com/2020/05/10/why…
Many non-expert contrarians assume that if infections per day (or hospitilzations per day, or COVID-19 deaths per day, or...) decrease, then that automatically means HIT was reached.
The contrarians typically apply this to Sweden or New York City.
judithcurry.com/2020/05/10/why…
7/M
This fails b/c HIT is about baseline conditions, without public health interventions or behavior changes (in technical terms: it's about R0).
In other words: factors other than herd immunity can decrease infections per day.
ncbi.nlm.nih.gov/pmc/articles/P…
This fails b/c HIT is about baseline conditions, without public health interventions or behavior changes (in technical terms: it's about R0).
In other words: factors other than herd immunity can decrease infections per day.
https://twitter.com/AtomsksSanakan/status/1286997934463160320
ncbi.nlm.nih.gov/pmc/articles/P…
8/M
Another contrarian myth is that immune cells known as T cells greatly limit the number of infections, allowing us to reach herd immunity with less people infected.
Anyone who grasps basic immunology can debunk that, as other immunologists have:
Another contrarian myth is that immune cells known as T cells greatly limit the number of infections, allowing us to reach herd immunity with less people infected.
Anyone who grasps basic immunology can debunk that, as other immunologists have:
https://twitter.com/profshanecrotty/status/1293346645560582144
9/M
An analogy on this might help those unfamiliar with immunology:
A key entering a lock is somewhat analogous to a receptor binding to the receptor's target.
T cells have their T cell receptor (TCR), and immune cells known as B cells have a BCR.
immunology.org/public-informa…
An analogy on this might help those unfamiliar with immunology:
A key entering a lock is somewhat analogous to a receptor binding to the receptor's target.
T cells have their T cell receptor (TCR), and immune cells known as B cells have a BCR.
immunology.org/public-informa…
10/M
B cells also make antibodies; these small proteins float freely and bind to viruses (like a key to a lock). That can prevent the virus from infecting your cells.
The BCR is basically an antibody the B cell keeps with it to bind stuff like viruses.
memorangapp.com/flashcards/110…
B cells also make antibodies; these small proteins float freely and bind to viruses (like a key to a lock). That can prevent the virus from infecting your cells.
The BCR is basically an antibody the B cell keeps with it to bind stuff like viruses.
memorangapp.com/flashcards/110…
11/M
The BCR can recognize freely floating virus.
In contrast, the TCR *cannot* recognize freely-floating virus. Instead, it needs your cells to take up the virus, and then present parts of the virus on the cell's surface on a molecule known as MHC.
faculty.ccbcmd.edu/courses/bio141…
The BCR can recognize freely floating virus.
In contrast, the TCR *cannot* recognize freely-floating virus. Instead, it needs your cells to take up the virus, and then present parts of the virus on the cell's surface on a molecule known as MHC.
faculty.ccbcmd.edu/courses/bio141…
12/M
To go back to our analogy:
If the virus is a key, then the BCR is a lock that fits that key, with no additional help needed.
And the TCR is a lock that only fits the key if the key has an adaptor (or keychain) attached.
MHC is the keychain.
To go back to our analogy:
If the virus is a key, then the BCR is a lock that fits that key, with no additional help needed.
And the TCR is a lock that only fits the key if the key has an adaptor (or keychain) attached.
MHC is the keychain.
13/M
T cells known as CD8+ T cells kill virus-infected cells that show virus proteins on MHC.
So these T cells don't greatly limit infection: the TCR's function here *depends* on cells getting infected. That's immunology 101.
westburg.eu/immunotherapy-…
T cells known as CD8+ T cells kill virus-infected cells that show virus proteins on MHC.
So these T cells don't greatly limit infection: the TCR's function here *depends* on cells getting infected. That's immunology 101.
westburg.eu/immunotherapy-…
14/M
CD4+ T cells, in contrast, don't kill certain types of cells that present virus to them.
But these CD4+ T cells limit infection by encouraging B cells to make antibodies. That flies in the face of what contrarians (who don't grasp immunology) say:
CD4+ T cells, in contrast, don't kill certain types of cells that present virus to them.
But these CD4+ T cells limit infection by encouraging B cells to make antibodies. That flies in the face of what contrarians (who don't grasp immunology) say:
15/M
So if someone makes the following claims to u, they're misleading u on immunology:
- 'T cells will help us get to herd immunity early, way beyond what we see with antibodies!'
- 'Sweden (New York City, or some other place not at baseline) achieved herd immunity!'
So if someone makes the following claims to u, they're misleading u on immunology:
- 'T cells will help us get to herd immunity early, way beyond what we see with antibodies!'
- 'Sweden (New York City, or some other place not at baseline) achieved herd immunity!'
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