More on Video Game You

Now that I’ve had my rest and about a gallon of mango juice, I’ll continue on talking about Halo 4¾ : Immunecraft. But before I move onto the specialty classes of white blood cells, I forgot to mention a few base classes. Besides macrophages, other specialized white blood cells the are part of the nonspecific immune response include neutrophils, eosinophils, basophils and mast cells. Neutrophils engulf pathogens and infected cells like macrophages, but don’t keep any trophies after (they’re not APCs, antigen presenting cells). The other two ‘Phils and the mast cells release nonspecific toxins in the presence of invaders. So they’re your buddy with the flamethrower, that can maybe get too excited and maybe burn down more buildings than you’d like. But Flamethrower Carl’s enthusiasm does attract the attention of the other players; basophils and mast cells secrete histamine to dilate the capillaries and make them leak. The leakiness allows macrophages and neutrophils to reach a given infection site and, when signaled, the special forces can move in.

B Cells and T-cells are these special forces. Both are produced in the bone marrow, but the T-cells get upgrades by maturing in the thymus. These cells arrive when an antigen presenting macrophage activates a circulating helper T-cell. This is the “go” signal and starts a chain reaction of immune responses faster than you can think about saying “domino”. Helper T-cells divide and activate B-cells and cytotoxic T-cells which in turn start dividing, kicking ass and taking names (not in that order). Cytotoxic T-cells are your hit men with machine guns that can hone in on an enemy and riddle it full of holes (literally, they use enzymes to “pop” cells). They are great for attacking viruses in infected cells. B-cells are a bit more clever, they specialize into plasma cells which produce antibodies specific to the invader in question. Besides gassing out the enemy with antibodies, B-cells can specialize into memory B-cells in order to “record” the antibodies needed for a particular pathogen. Subesequent infections of the same pathogen are then fought off much faster. Finally, there is the underappreciated suppressor T-cell, a helper T-cell that gets out and reminds everyone (via chemical signals) that the immune system does not follow a scorched earth policy so PLEASE just tone it down guys, OK???

Probably the niftiest thing about this whole immune response/video game is that the B-cells and T-cells activated are activated because they are already specific to whatever is already infecting you. Your body can tell the FUTURE. Except it can’t. There are BILLIONS of B- and T-cells in your body, each with different surface receptors that can be activated by different antigens. So it’s a probability thing, like those monkeys on typewriters, but instead of Shakespeare, they come up with billions of cell surface receptors. Of those billions, your body can single out the exact one to save you from misery or even death.

 

Source

-. 2010. GRE Subject Test: Biology 5th Ed. Kaplan, New York.

John Mayer was Wrong

Your body is not a wonderland, it is a first-person shooter and you are the map. OK, fine, maybe it’s more like Starcraft than Halo, but you get the point. There is an army (your immune cells) that needs resources (energy, acids, etc) and there are invaders (pathogens) trying to either steal those resources or take over your base (you). Counting your body’s natural microbiota (non-harmful bacteria), the video game of you includes NPCs. Usually they’ll help you out by either direct confrontation of pathogens, or outcompeting for resources. Like a real NPC though, they’re easily overwhelmed and will destroy your shit if they’re in the wrong place at the wrong time. E. coli, for instance, are great in the large intestine and will even produce vitamin K for their host, but if they get anywhere else they will wreak havoc on your body. So always wash your hands after using the bathroom or you will lose the game and respawn is a bitch.

Natural microbiota are part of the body’s nonspecific defenses. Your skin is the most obvious defense and does not get enough credit. Bacteria and viruses cannot penetrate intact skin, you would be constantly fighting off large and small infections otherwise. Sweat also lowers your surface pH, to make your skin less desirable to pathogens. Simple stuff, yeah, but what about your tears? Your tears contain lysozyme, an enzyme able to annihilate bacterial cell walls and certain viral capsids. So these are like the wall and uh…anti-enemy spray in video game you. Okay the analogy is breaking down a little, but I have one more! Here’s where Halo works better as a point of reference. I can’t aim for crap in first-person shooters, but I know people that can, if I gave one of them a rocket launcher they would be my macrophage. They will get. Shit. Done. Anything without the team color (or antigen) gets blown to next Tuesday, no questions asked. In your body, macrophages actually engulf pathogens and infected cells. Some bacteria will plan for this, but that’s a topic for another day. The macrophages are pretty indiscriminant beyond friend vs. foe, but they display antigens like little war trophies (less medal, more severed ear) on their surface to other cells that can discriminate. What are these discerning characters? I’ll tell you tomorrow. Mama’s tired and going to watch her stories.

Source

-. 2010. GRE Subject Test: Biology 5th Ed. Kaplan, New York.