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The Dendritic Cell is looking for just the right Helper T Cell that can bind its specific receptor to the antigen.
And if a matching T Cell is found the two cells interlock. But then there needs to be a second signal,
only then does a Helper T Cell activate.
The genes that are responsible for the MHC molecules are the most diverse genes in the human gene pool, leading to a huge variety of MHC molecules between individuals.
Around five days to a week after the wound was inflicted Helper T Cells arrive at the site of infection,
Helper T Cell commanders at the site of an infection play the role of amplifiers that use the inherent power of the Innate Immune System to overcome harsh enemies.
Some Helper T Cells become Memory Helper T Cells. Whenever you hear that you are immune to a disease, this is what this means. It means that you have living memory cells that remember a specific enemy.
What makes B Cells special, and very dangerous for friends and foes, is that they produce the most potent and specialized weapon the immune system has at its disposal: Antibodies.
Antibodies are basically B Cell receptors.
Antibodies are stuck to the surface of B Cells and work as their B Cell receptors, which means that they can stick to an antigen and activate the cell.
The antigens that can activate T Cell receptors have to be pretty short because the MHC molecule can only carry short antigens.
And B Cells do not need an MHC molecule, they don’t need to get a presentation from another cell like T Cells do.
Virgin B Cells sit in your lymph nodes, where they bathe in lymph and take in all the antigens that are transported through the area from the closest battlefield. Their B Cell Receptors can just grab big chunks of antigens directly from the lymph
complement proteins attached to an antigen makes it about 100 times easier to activate a B Cell than it would be to activate it without the complement.
after a Helper T Cell has been activated and has made a lot of clones of itself, one group of the Helper T Cells moves to the battlefield while the other group goes off to activate B Cells for real.
in order to be properly activated, B Cells have to become antigen-presenting cells.
a B Cell takes a complex antigen and turns it into many processed, simpler pieces that are then presented to the Helper T Cell.
if a Helper T Cell can connect to the antigen presented by a B Cell, there is an enemy out there and both cells are able to recognize it.
A battle needs to occur and dead enemies, which are big chunks of antigens
need to float through the lymph node. Here, a B Cell, with a specific receptor needs to connect to the antigen. If the dead enemy is covered in complement, activation will be much easier.
This will activate the B Cell, which makes a lot of copies of itself and produces low-grade antibodies, but the B ...
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In the meantime, a Dendritic Cell needs to pick up enemies at the battlefield and...
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which are put in the MHC class ...
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it needs to find a Helper T Cell that is able to recognize the antigen with it...
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The B Cell breaks the big chunk of antigen
down into dozens or hundreds of small antigens
and begins presenting them in MHC clas...
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An activated B Cell that is presenting hundreds of d...
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needs to meet a T Cell that can recognize one of these antigens with its specific T Cell receptor, which is the second signal for the B Cell. Only if this exact sequence of eve...
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Your B Cell that was properly activated through the two-factor authentication now changes. It has waited its whole life for this moment. It begins to swell, to almost double its size, and transforms into its final form: the Plasma Cell.
The Plasma Cell now begins producing antibodies for real. It can release up to 2,000 antibodies per second that saturate the lymph and blood and the fluids between your tissue. Like the Soviet rocket batteries in World War II that could send a never-ending barrage of missiles on enemy positions, antibodies are made in the millions and become every enemy’s worst nightmare, from bacteria to viruses or parasites. Even cancer cells. Or, if you are unlucky and have an autoimmune disease, your own cells.
a graduate student did some work with chickens who were missing their bursas and subsequently found that they were unable to produce Antibodies. He discovered B Cells, the factories that produce Antibodies, and that they were made in this weird little organ in birds,
Antibodies themselves are not particularly deadly. They are actually nothing more than mindless protein bundles that can stick to antigens.
The most common Antibodies are shaped like little crabs with two pincers and they are seriously pretty tiny:
In a sense they are sort of comparable to the proteins of the complement system—which are also nothing more than tiny proteins that float around—but
This is basically what they are: Tiny crab-like proteins that are extremely good at grabbing on to the enemies they were made for,
IgM Antibodies are usually the majority of Antibodies B Cells produce when they get activated.
Especially against viruses, IgM antibodies are a powerful early weapon that can slow down an infection.
So IgM Antibodies are the first Antibodies to be deployed—which
In general IgG is not nearly as good at activating complement as IgM is, but it is still pretty solid at it.
Another thing that makes IgG Antibodies special is that they are the only Antibodies that are able to pass from the blood of a mother into the blood of an unborn fetus via the placenta.
IgA is basically a sort of bouncer that protects the entrance doors to your insides, your eyes, nose, mouth, etc. from unwanted guests, by neutralizing pathogens early on before they have the chance to get in and establish a foothold.
Other than protecting and cleaning up your gut, IgA also protects our babies. When mothers are breastfeeding they provide their offspring with a large amount of IgA Antibodies through their breast milk. These antibodies then cover the gut of the newborn and protect its still-fragile intestinal tract from infections.
The original purpose IgE Antibodies serve is to protect you against infections by huge enemies: Parasites. Especially worms.
B Cells are not locked into making a certain class of Antibody—they always start with IgM
Having a nasty cold or a gut infection and need a lot of antibodies in your snot or stool? Make IgA! Having a parasitic worm in your intestines? Make IgE! A lot of bacteria have infected a wound? Make IgG flavor one! There are a lot of virus-infected cells? Please, more IgG flavor three!
spleen is a sort of lymph node for your blood but there is more! This tiny organ is the main source for superfast responding IgM Antibodies in your blood.
The spleen filters your blood and when it finds enemies here it can quickly activate B Cells that rapidly make IgM Antibodies.
your mucus is also saturated with deadly IgA Antibodies.
how it is possible that you have a sack filled with literal acid inside of you? Well, the mucosa inside your stomach acts as a barrier that keeps the acid at a distance and protects the cells making up your stomach wall.
