Our body has a powerful army that protects it from various types of threats. These threats can come in the form of mechanical injuries, the entry of germs, or the entry of other foreign particles like dust. This personal army is called the immune system. Every day, we encounter a huge number of bacteria, viruses and other disease-causing organisms. However, we don’t fall ill every other day which is due to our immune system – an army of cells that is always roaming our body, ready to ward off any attack. The immune system can be broadly divided into two parts – innate and adaptive immunity.
Innate immunity or non-specific immunity is the body’s first natural defense to any intruder. This system doesn’t care what it’s killing. Its primary goal is to prevent any intruder from entering the body, and if it does enter, then the immune system kills this intruder. It doesn’t differentiate between one pathogen and another. The first component of this defensive system is your skin. Any organism trying to get into the body is stopped by the skin, our largest organ, which covers us. Secondly, there is the mucous lining of all our organs. The sticky, viscous fluid of this lining traps any pathogens trying to get past it. These are the physical barriers. However, we also have chemical barriers, such as the lysozyme in the eyes, or the acid in the stomach, which kill pathogens trying to gain entry. The genitourinary tract and other places have their own normal flora, or microbial community. These compete with pathogens for space and food, and therefore also act as a barrier. The next line of defense is inflammation, which is done by mast cells. These cells are constantly searching for suspicious objects in the body. When they find something, they release a signal in the form of histamine molecules. These alert the body, and blood is rushed to the problem area. This causes inflammation and also brings leukocytes, or white blood cells, which are soldiers in our body’s cellular army. Once they come, all hell breaks loose! Sometimes however, the intruder may not be germ, but rather a harmless thing like a dust particle. The body still causes a full immune reaction to this intruder, which is how allergic reactions occur.
In the fortress of our body, the leukocytes are VIPs. They have an all-access pass to the body, except, of course, to the brain and spinal cord. Our leukocytes come in many types. Those that belong to the innate system are the phagocytes. These cells can either patrol your body, like the neutrophils, or they can stay in certain places and wait for their cue. Neutrophils are the most abundant cells. They patrol the body and can therefore get to a breach site very quickly. These cellular soldiers kill the infectious cell and then die, which leads to pus formation. There are also the big bad wolves, or the macrophages. These cells are like hungry, ravenous monsters who simply engulf unwanted pathogens. Instead of roaming freely in our blood, they are collected in certain places. These cells can consume about 100 pathogens before they die, but they can also detect our own cells that have gone rogue, such as cancer cells, and kill them too.