PATHOGEN INVASION!! HOW YOUR BODY PROTECTS YOU?
Everyday we are invaded by BILLIONS AND GAZILLIONS of pathogens from all over the place. From the cleanest surgery room to the dirtiest toilet you can find on planet, there's always so many bacteria and viruses invading us. So how our body keep us in the pink of health?Thanks to the god creation, Human body inborn-ed with multilayered protection to keep us healthy. It comes down to two kind of protection :
1. INNATE IMMUNITY
This is the type of immunity that is mediated by cells and proteins that are always present, they're swift in action, thus it is the first line of defense against pathogen.
1) Anatomic barrier to pathogens :
2) Inflammation
Remember that feeling when a splinter pierced through your skin? The injured site starts to get hot and pain and reddish. By that, you're looking at inflammation taking place. Inflammation aims to bring the fighter cells and molecules to the site of injury, to fight off the invading organism entering from your wound.
3) Complement system
It is a chemical cascade in the immune system that helps/"complement" the antibodies to fight off infection. This cascade is done by myriad of plasma proteins synthesized from the liver. Its main purpose is to play "TAG game" on pathogens and poke some holes on it and lead to its destruction.
CELLS RESPONSIBLE FOR IMMUNE SYSTEM
Leukocyte or white blood cell play the lead actor on the scene of war against pathogens. In any war, there's a need for combat unit and military structure. So does our body.
PHAGOCYTE
Phagocyte means an eating cell. Nyom nyom nyom. Chewing away those pathogens. To engulf those pathogens, it stretched out its portion of it's membrane, wrapping around the particle or pathogen and secrete some enzymes for it to digest the particle. They're the active seeker of foreign particles in body, and are able to react to cytokines. ( an inflammatory mediator to trigger immune response)
MACROPHAGES
In Greek, it means "large eaters" compare with phagocyte. It is a large cell but it's able to slip through vascular wall and seek pathogens to kill. This is important as early prevention of pathogen into the blood circulation can decrease the chance of wide spread infection. It also releases cytokines to recruit other leukocyte to help in fight. This macrophage will start engulf once it's receptor bind to the antigen by bacteria or pathogen, releasing reactive oxygen species in the process.
MAST CELLS
Mast cell commonly present in connective tissue adjacent to blood vessels and it is found in mucous membrane too. Mast cell release histamine through degranulation in response to a variety of stimuli
- physical injury
- binding of antibodies to mast cell ( which is seen in allergic reaction / hypersensitivity reaction)
- and stimulus from product of complement cascade
Histamine helps to dilate the blood vessels while cytokine released by mast cell will attract other fighter cells like neutrophils, make their way to the site.
NEUTROPHIL
100 billions of neutrophils are being produced everyday in a healthy adult. They're also categorized under granulocyte, due to presence of granules inside the cytoplasm. Like macrophage, it also leave reactive oxygen species as byproduct. They are the most abundant type taking over 50-60% of leukocytes count. It is the first fighter to arrive at injury site.
DENDRITIC CELLS
They are phagocytic cells that present in tissue and are exposed to the external environment. It can be found mainly on the skin and inner lining of stomach and etc. Dendritic cell resembles a dendrite which is a part of neuron. But it has nothing to do with nervous system. It serves an important role in antigen presentation, which means presenting part of bacteria's molecule as a map for leukocytes to identify them. Imagine a dog which smell belongings of some thief, is able to identify the same odor from the thief.
2. ADAPTIVE IMMUNITY
I will talk about this in part 2. Stay tune!!
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