“Military action is important to the nation. It is the ground of death and life, the path of survival and destruction so it is important to examine it.”
Master Sun Tzu said this a long time ago, even before we became conscious of our never-ceasing battles with unseen enemies—Microbes. Believe it or not but you were first engaged in such battles even before you were born and you will remain engaged in them until you are dead. Invasive by nature, such microorganisms were discovered in 1665 while humans have been here for some million years. How is it that we were not even aware of their existence, but still managed to survive? It is because we were born with a built-in system of defense—the Immune System. It is a gift that God bestowed upon us all.
The concept of Immune System was first discovered in 1665. After a great amount of research, we can safely classify it into two branches:
- Innate Immune System (Non-Specific)
- Adaptive Immune System (Specific)
In this piece, we will not discuss these branches separately; instead, we will try to consider a simple question:
“What happens inside your body when a pathogen enters it?”
Imagine that it is a nice day and you are walking in the nearby woods when suddenly you run into a thorn-bush and hurt yourself! Skin—the first line of defence—is ruptured. Bacteria seize this opportunity and enter your body; they start multiplying and damaging the body. Macrophages are the first to react to this invasion; they swallow up the enemies and break them down through an enzyme called Lysozyme. Meanwhile, they do their secondary job as well: transmitting information to the upcoming army and making the battle easier. When the battle starts getting harder, they send for Neutrophils. Neutrophils leave their patrol route at once and rush to the battlefield. Neutrophils are so intense and devoted to the task that they even kill the body’s healthy cells in the process. This is why they are programmed to commit suicide after 5 days, so as to prevent further loss of energy in the body.
But what if the Neutrophils also prove to be insufficient?
Then the Intelligence is called from the brain. The brain sends its spies to the battlefield which are called Dendritic cells. They collect samples of antigen, rip them apart and process them. Now they have to make a decision of utmost importance. Should they call Antiviral bodies which eradicate the infected cells or should they call Antibacterial ones? In this case, they call latter ones. They carry the torn pieces to the lymph—a factory where Helper T-Cells and Killer T-Cells are produced. Helper T-cells are born with a specific setup for a specific antigen. It’s like a specific key to a specific lock. Dendritic cells look for the exact same setup for the antigen that has entered. Once found, helper T-cell starts replicating into thousands. Some of them turn into memory cells, some travel to the battlefield, and the rest go to the lymph node to meet with B-cells.
Like the T-cell, B-cell is also born with a specific setup.
When T-cell finds an antigen with the same setup, B-cell is activated and starts replicating, and producing Antibodies. Antibodies are engineered with a specific system to bind to the surface of the intruder. A problem is that antibodies are of different types. Thus, Helper T-cells tell B-cells which type of antibody is required for each intruder.
Meanwhile, the situation on the battlefield starts getting worse as Macrophages start getting tired. Here Helper T-cells play yet another role; they order the Macrophages to fight more. Next, the antibodies arrive at the scene. They stun, disable, and kill the microbes. Finally, the enemy is wiped out. After eradication of the enemy, nearly all the cells commit suicide to prevent further loss of energy but a few remain. These are Memory cells; they store data of the specific intruder.
If the same intruder happens to come back, they get rid of it before you even notice.
Now it was the simplest and briefest possible explanation of the immune system. Imagine how complex our body is! Indeed, the greatest of knowledge lies deepest in nature.