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October 20, 2022 - January 9, 2023
In their active shape, however, they can change the shape of other complement proteins and activate them.
All you really need to know is that C3 is sort of the most important complement part, the first match that needs to catch fire to start the cascade. When it does, it breaks into two smaller proteins with different shapes that are now activated. The first match is lit!
it anchors itself very tightly to the bacterium’s surface and does not let go.
In its new form it is able to grab other complement proteins, change their shape, and merge with them.
An amplification loop begins.
Within a few seconds of the first complement protein activating, thousands of proteins cover the bacterium all over.
Thousands of C3a flood away from the site of battle, screaming for attention. Passive immune cells like Macrophages or Neutrophils begin smelling them, picking them up with special receptors, and awake from their slumber to follow the protein tracks to the site of infection.
complement does exactly the same job as cytokines, only that they are passively generated and don’t need to be generated by cells, like cytokines do.
The membranes of cells and bacteria are negatively charged—and as we learned from playing with magnets, the same charges repel each other. This charge is not so strong that it can’t be overcome by a phagocyte, but it does make it considerably harder for immune cells to grab bacteria. But! Complement has a positive charge. So when complement proteins have anchored themselves to the bacteria, they act as a sort of superglue,
This process is called opsonization, which comes from an old Greek word for a delicious side dish.
On the surface of the bacteria the C3 recruitment platform changes its shape again and starts to activate another group of complement proteins.
A Membrane Attack Complex
They stretch and squeeze, until they rip a hole into it,
and its insides spill out. Which makes it die quite quickly.
the enemy it might be the most useful against are ...
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Without complement, virus infections would be a lot more deadly.
Let us summarize briefly what we learned so far about the Innate Immune System before we move on.
Your body is wrapped in an ingenious self-repairing border wall that is incredibly hard to pass and that protects you extremely efficiently. If it is breached, your Innate Immune System reacts immediately. First your black rhinos, Macrophages, huge cells that swallow enemies whole, appear and dish out death. If they sense too many enemies they use cytokines, information proteins to call your chimp-with-machine-gun Neutrophils, the crazy suicide warriors of the immune system. Neutrophils don’t live long and their fighting is harmful to the body because they kill civilian cells. Both of these
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Bacteria are not just pushovers but have developed a number of strategies to hide or avoid the first line of defense.
pathogenic soil bacteria in your infected wound employed defenses, multiplied quickly, and gained a real foothold. They nourish themselves with the resources that were meant for civilian cells and begin defecating everywhere, releasing chemicals that hurt or kill cells, civilians, and defenders.
Pus is the dead bodies of millions of Neutrophils that fought to the death for you, mixed in with ripped-apart remains of civilian cells, dead enemies, and spent antimicrobial substances.
While the battle has been raging, the intelligence portion of your innate immune system has been quietly doing its job in the background: The Dendritic Cell is on its way.
they have two of the most crucial jobs of your entire immune system: They identify what kind of enemy is infecting you, if it is a bacterium or a virus or a parasite. And they make the decision to activate the next stage of your defense: Your adaptive immune cells, your heavy, specialized weapons that need to come in if your innate immune system is in danger of being overwhelmed.
The Dendritic Cell is like a careful connoisseur of the fluids of your body that flows around between your cells.
The Dendritic Cell is always looking for a few very particular tastes—the flavor of bacteria or viruses, the taste of dying civilian cells, or the taste of alarm cytokines from fighting immune cells. When it takes a sip and recognizes any of these flavors, it knows that danger is present and goes into a more active sampling mode.
Not only is the Dendritic Cell able to distinguish if an enemy is, for example, a bacterium, it can distinguish between different species of bacteria and knows what sort of defense is needed against them.
After a few hours its internal timer runs out. Suddenly the Dendritic Cell stops sampling.
The Dendritic Cell takes off and leaves the battlefield—its destination is the great gathering place, the intelligence center where millions of potential partners await.
In any way, the battlefield snapshot, the living information carrier, needs to be delivered to a lymph node. To get there, the Dendritic Cell has to enter the Immune System Superhighway: The Lymphatic System
the megacity and superhighway network of your immune system: The Lymphatic System
The lymphatic system is responsible for this job. It sort of constantly drains your body and tissues of excess fluid and delivers it back to the blood where it can circulate again—if it didn’t, you would swell up like a balloon over time.
Your lymphatic system begins as a tight and complex network of capillaries spread throughout your tissue.
There is only one direction, as very gradually small lymph vessels merge into bigger ones, which then continue to merge into larger ones. Since the lymphatic system has no real heart, the water flows slowly.
Your heart pumps and transports nearly 2,000 gallons of blood through your body every single day, while your lymphatic system only transports around three quarts from your tissues back to your blood.
it is also your waste management and alarm system.
transports them directly to your immune system intelligence centers, your lymph nodes, where they are filtered and analyzed.
maybe its most important job is to serve as a superhighway for immune cells.
Your bean-shaped Lymph Node megacities—the organs of your immune system. You have around 600 of them spread all over your body.
The Spleen is a sort of large lymph node, about the size of a peach but bean shaped. Just like lymph nodes it is a sort of filter but with a much larger scope. For one, the spleen is the place in your body where 90% of your old blood cells are filtered and recycled when their life comes to an end. On top of that your spleen stores an emergency reserve of blood, about a cup, which is invaluable if something bad happens and you could use a bit of extra blood in your body. This is still not all, 25 to 30% of your red blood cells and 25% of your platelets (remember, the cell fragments that can
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The main home for another immune cell
the Monocyte. Monocytes are basically reinforcement cells that can transform into Macrophages and Dendritic Cells.
they come in as backup. Once they enter the site of infection, they stop being Monocytes and transform into fresh Macrophages.
The other half of your Monocytes sit in your spleen as a reserve emergency force.
the spleen really is just a huge lymph node that filters your blood (and not your lymph fluid,
Your tonsils are something like a center of your immune system intelligentsia in your mouth.
Microfold Cells, very curious cells that grab all sorts of stuff from your mouth and pull it deep into the tissue, where they show it to the rest of the immune cell to check out.
the Lymphatic System is your fat transportation system. It picks up food fats around your intestines and dumps them into the bloodstream to be further distributed.
Helper T Cells! Specialist cells from the Adaptive Immune System were forged just for this particular battle and they exist only to fight this specific soil bacterium
The specialist forces of the Antibodies have arrived! Although they are made from proteins just like complement, antibodies are very different.
With help from the Antibodies, your soldiers can suddenly see them much more clearly and they now seem much more tasty than before, now that they have been opsonized.
