I’ve been stuck with a little cold the last couple days and been quite slow and not as productive with my lab report as I’ve wanted to. Tomorrow I’m driving to Munich for my visa interview, after that I will be in Frankfurt for another week followed by a couple days in spain. From there I go directly to the US, which means I don’t have much time before I start my next lab rotation, and I really want to this finish this report before starting a completely new topic.
Dwelling over the feeling how nice it used to be to breath without a blocked nose, I decided to write this post about the immune system. Advanced immunology was actually one of my favorite modules in uni, which was also thanks to our amazing professor – she was very passionate about the topic and extremely good at explaining. I’ll simplify the topic quite a bit, so we don’t get caught up in details and can appreciate the overall ‘how’ it works.
The immune system can be divided in 2: the innate and the adaptive immune system. For this scenario we’ll look at how these 2 systems (inter)act with invaders (pathogens) it’s never seen before.
Innate immune system -> also referred to as the first line of defense, aka the traffic cops
A key aspect about the innate immune system, is that its non-specific, it simply eliminates everything that is non-self. One can imagine it like a diverse group of traffic cops which are specialized in detecting invaders, independent of who these invaders are.
In our bodies the policemen are specialized cells involved in innate immunity such as Natural killer (NK) cells and macrophages. They usually detect pathogenic invader based on the structural features, one can imagine them like limbs, and destroys them. The two other roles they have are a) calling for back up (the SWAT team) by directly sending out inflammatory factors which alert other immune cells and b) change gene expression in specialized cells, so they can produce and send out more inflammatory factors, so more SWAT teams and other Pros can be alerted. The SWAT team represents other immune cells, such as neutrophils and monocytes, which take about 20-24hrs to alert (via the inflammatory mediators).
Adaptive immune system – aka the specialized fighter pros
So now, the SWAT team is hard at work, but the invader is just to skilled at martial arts, that the SWAT team can’t handle them, which leads to the next line of defense: the adaptive immune system (consisting of B and T lymphocytes). These are teams of highly skilled fighters that a) get custom training to specifically focus and fight only one enemy and b) can memorize enemies. For T lymphocytes, this is done by literally presenting the young fighters parts of the enemy (antigen presentation) in their training camp (thymus – part of our lymphatic system) so they recognize (via antibodies) and neutralize them when they’re sent out.
The “invader parts” that are presented to young fighters are derived from the innate immune cells, particularly macrophages, which destroyed, ate them, and subsequently brought the pieces to the training camp. Luckily, the specialized fighters already got alerted to start preparing along with the SWAT team via the inflammatory mediators. The B and T lymphocytes are derived from the bone marrow. While B cells also mature in the lymphatic system, they mature through a different method, called differentiation. (a detailed explanation can be found here: https://www.khanacademy.org/test-prep/mcat/organ-systems/the-immune-system/a/adaptive-immunity)
The training of the specialized T lymphocyte fighters is extremely selective, making sure they attack the pathogen efficiently and really only attack the invader – not its own cells and tissue (this would be autoimmunity). When an ideal fighter is trained, the same skills and tools are applied to other young fighters, creating an army of specialized fighter tools ( -> antibodies mass produced by B cells) which are expelled at high numbers into our circulation and lymph. Lastly, after the enemy has been eliminated, there are memory B-cells, specialized cells in low numbers that remember the invader in case of a reoccurring attack.
Overall the immune system is much more complex, specific and not black/white in their roles and functions. This only serves as brief and simplified introduction for basic understanding. Either way, our immune system is really genius in making sure we’re healthy and survive.