The cold and flu season is upon us and so let’s spend some time reading about how amazing the human immune system is. You’re going to look at this sneeze picture very differently 10 minutes from now. Here are the 5 coolest hacks in the human immune system:
5. B cells are like the NSA, kind of.
Sleepers and secret agents all come from somewhere – private contractors, FBI, CIA, and CCIS (the NSA has its finger in a lot of pies, so probably there too). B Cells in your immune system are very similar, except there is no conspiracy theory here, its all science and for the betterment of your health. B cells are white blood cells in your body whose job it is to feel their environment for possible intruders. But, rather than one B cell sensing for billions of different intruders (NSA), there are billions of B cells sensing for individual intruders. B cells survey for intruders using a B Cell Receptor that is on their surface. When they bump into an intruder that happens to bind to the receptor, a RED ALERT is triggered. But as a safe guard, the B Cell can only start blitzin’ out antibodies when the intruder is confirmed by a collaborator cell, a T Helper Cell. If a T Helper Cell concurs, the B cell turns into a beastly arms factory that pumps out billions of antibodies with the same binding abilities as the B Cell Receptor. This way, those mass produced antibodies can bind to that intruder and neutralize it. Compared to real life, rather than overcoming intruders with bullets and missiles, you immobilize them with a hugs.
Take that, intruder.
4. Memory B/T Cells
In Malcolm Gladwell’s, Blink, he summarize an amazing and real story from the 20th century where an ‘old school’ commander of an army was set up as the leader of a rogue terrorist organization (metaphor = Iraq) that was fighting against a mighty and omnipotent country (metaphor = USA). The rogue leader was so cunning that the mighty country had no choice but to cut all telecom communications leaving the the rogue group without the ability to communicate with their people in the field and their pilots, or so they thought. Surprisingly, however, the planes kept flying, supplies kept moving and the rogue army kept ahead. How did the rogue commander do it? ”He borrowed a forgotten technique from World War II and used lighting systems”.
The rogue commander had years and years of experience and remembered tricks from the past. This is like the Memory B/T Cells. After they have been in a battle, they are genetically promoted to the level of Commander and for decades will continue to survey your blood for intruders. If the intruders that they dealt with in the past ever return, they are ready to sound the alarms and neutralize them. Ever wonder why your MMRP vaccinations that you received when you were a baby are still working strong? Well its your Memory B/T Cells. As you read this sentence, they are coursing through your veins looking for measles, mumps, rubella and pertussis waiting to neutralize them before they become a problem.
How incessant and great are the ills with which a prolonged old age is replete.
-C. S. Lewis
3. Membrane Attack Complex (MAC)
The next time you think about hurting your liver by drinking excessively, think again. Your liver is responsible for creating some very important immune system proteins that make up what is called the Complement System. Billions of these Complement System proteins are circulating through your blood system right now and when they come into contact with the right pathogen, one of the deadliest immune system nanostructures, the Membrane Attack Complex (MAC), automatically kicks into action. The MAC forms on the surface of bacteria, destroying their membranes and causing major cell disruption and death.
If you’ve played Portal [LINK] then the the complement system will be familiar to you. You fire your weapon at a wall (Complement proteins) and when they hit the wall they form a large hole (MAC). This allows you to pass back and forth through the hole. If you did this on the side of a giant aquarium, you’d probably get wet.
2. MHC (Class 1)
The Major Histocompatibility Complex (MHC) is surely a mouthful, but I assure you that it’s an awesome safeguard of your cells. There are a couple kinds of MHC and so we’re going to focus on Class 1 here. MHC is a protein complex that exists in pretty much every human cell in your body that has a nucleus (all cells but your red blood cells). When your cells get infected with a virus, like the flu virus, just like a fort under attack – they put up a flag, start a smoke signal, or send a tweet to tell the rest of your body that they have been infiltrated – the MHC is a critical part of how they send this message to the surface of your cell.
When a virus hijacks your cell’s machinery to replicate itself, your cell breaks down some of the viral proteins into small bits called viral peptides. These peptides travel around in the cells aimlessly, but can come into contact with a protein called TAP (that teleports the peptide into into a protein factory in your cells called the ER (http://en.wikipedia.org/wiki/Endoplasmic_reticulum). The MHC resides within the ER and thats where these viral peptides ultimately bind to the MHC. Once the viral peptide is locked and loaded, the MHC is sent to the cell surface and is presented to your immune system like a distress flag. Natural Killer Cells that are circulating in your blood feel around on the surface of your cells and interact with the MHC distress flags. If a Natural Killer Cell notices that a viral peptide is present, it unleashes its arsenal of weapons, notably GRANZYMES and PERFORIN (see Hack #2).
2. Natural Borne Killer Cells (Perforin & Granzymes)
NK Cells travel around your body and seek out abnormal cells. They look for cancer cells and cells infected by viruses. When they come into contact with MHC containing a foreign peptide (viral peptide) it pulls out its bazooka and directs it at the cell. But, rather than a rockets, it unleashes a wrath of ninja proteins called granzymes and perforin. Perforin forms a ring, binds to the surface of the infected cell and creates a hole in the membrane of the cell allowing the granzymes to enter. Granzymes enter, and their job is to hit the big red button, yes, the classic self destruct button of the cell. The self destruct is called, APOPTOSIS (eh-pop-toe-sis, its Canadian, Eh).
See Natural Killer Cells in action (killing a cervical cancer cell).
1. Apoptosis (Programmed Cell Death)
This heart shaped nucleus may make Apoptosis seem like flower power lovin’ from the 60’s, but this is a catastrophic event for that cell. Famously, Joseph Stalin ordered that everything be burned as the Russians retreated toward Stalingrad when the Nazi’s were hot in their pursuit. This is called a scorched earth campaign. Mix that with the ideology of a self sacrificing Samurai, and you’ll arrive at Apoptosis, a.k.a, Programmed Cell Death. Apoptosis is the ultimate selfless sacrifice that occurs in your body in billions of cells every day. Apoptosis is happening in you right now. Apoptosis can be induced by your immune system when pathogens are suspected of infecting your cells, or by cells that believe that they themselves may have become cancerous. Within those cells the metaphorical big red self destruct button is pressed to ensure that their short-coming will not propagate to other cells or bring harm to your body.
First to go is your mitochondria, the main power station of your cell. With the power grid down, it is only a matter of time before other infrastructure fails and collapses. Your cell shrinks because enzymes break down the cell membrane, the genomic DNA becomes compact, the surface starts blebbing and ultimately the cell fragments into many spherical vesicles called apoptotic bodies. The grand finale is that those apoptotic bodies are eaten (phagocytosed) in a cannibalistic manner by other immune cells called Macrophages.
So next time you try to do this math:
Remember that your immune system is one of the most sophisticated war machines on planet earth.