Immune System in Simple Language
Dr. Nancy Qusba M.D. is a top Emergency Physician in Downers Grove, IL. With a passion for the field and an unwavering commitment to their specialty, Dr. Nancy Qusba M.D. is an expert in changing the lives of their patients for the better. Through their designated cause and expertise in the field, Dr. Nancy Qusba M.D. is... more
I am so fascinated by everything about the immune system, how it works 24/7 and keeps us safe.
One way to start understanding the immune system is by viewing the human body as a castle, surrounded by a high brick wall and protected by soldiers. We are surrounded by millions of microorganisms, like bacteria, viruses, and fungi.
Any of them can attack our body at anytime, so our immune system needs to be ready to fight them back. An antigen is an intruder and an antibody is a protector.
Line of Defenses
Physical barriers (walls around the castle)
- Skin: The skin is the first line of defense. It's hard to penetrate, similar to the bricks that construct the castle wall, and provides a barrier to the intruder (pathogen).
- Mucous membrane: Secretions of the nose, eyes, mouth, and vaginal lining produce lysozymes, which is used to destroy incoming pathogens.
- Lungs: Thick, sticky mucus that is produced by cells in the respiratory tract, and the brushes (cilia) trap dust and microorganisms to prevent them from entering our lungs.
- Stomach: The acid in the stomach is mixed with a variety of digestive enzymes, all of which kill most of the microorganisms.
Chemical barriers
When pathogens (intruders) breach the body’s first line of defense (i.e. the skin or mucous membrane), within minutes our chemical barrier is activated as our defense system.
Immune cells are known as white blood cells, or leukocytes. These cells are similar to specialized units in our police departments, that run to the scene of the crime. They travel through the bloodstream to increase blood flow to affected areas and draw a great number of antibodies to fight the intruders. They also send special cells (phagocytes) to eat them up.
If pathogens succeed to penetrate the second line of defense, the third line of defense will act.
The third line of defense is the adaptive immune system. This is normally in a resting state, however, it'll be activated once the intruder sets off their alarm. When activated, the adaptive immune response is mediated by immune cells known as lymphocytes. These are B and T cells. B cells are highly specific, and will attack and destroy infected cells. Some of these B cells also become memory cells, which will help the body "remember" the disease and prevent the area from reinfection. T cells, also known as Helper T cells, activate B cells, attract microphages, and use cytokines (a chemical weapon), thus actively killing the cell.
When all three lines of our defense are breached, this is where we get sick and are subjected to diseases like HIV and cancer.
