A mosquito lands on your hand, bites, and sucks your blood. You feel an itch and see a red bump. That swelling is a sign that your immune system is protecting you.
The immune system is a network of cells, tissues, and organs that coordinate the body’s defenses against infections, illness, and disease. Without it, you’d be exposed to billions of bacteria, viruses, and toxins. In such a case, even a small cut or a common cold could be life-threatening.
The immune system relies on millions of white blood cells, known as leukocytes, to defend the body. These white blood cells are produced in the bone marrow and move through the bloodstream and lymphatic system.
The body has around 4,000 to 11,000 white blood cells per microliter of blood. They act like security guards, constantly monitoring the blood, tissues, and organs for any suspicious signs.
This system mainly works by detecting signals known as antigens. These molecular traces and foreign substances reveal the presence of invaders. Once leukocytes detect them, it only takes minutes for the body to activate an immune response to defend itself.
Since there are many threats to the body, the immune response must be adaptable. This means the body relies on different types of white blood cells to handle different threats in various ways.
White blood cells are divided into two groups: phagocytes and lymphocytes.
Phagocytes trigger an immune response by sending macrophages and dendritic cells into the bloodstream, where they destroy any foreign cells they encounter. They also pass on this information to the second group of cells to organize further defense, known as lymphocytes.
Lymphocytes, called T-cells (or lymphocytes), take the information from phagocytes and then seek out infected cells, quickly destroying them.
During this process, the immune system uses the information it gathers from specific antigens to begin producing specialized proteins called antibodies.
The core principle of the immune system is that each antigen has a corresponding antibody, which works like a lock and key to destroy foreign cells until the threat is neutralized. Typically, an immune response will eliminate a threat within a few days.
While this is happening, symptoms such as fever and swelling help the immune response. This is because a warm body can slow the reproduction and spread of bacteria and viruses, as they are sensitive to temperature. Damaged cells release chemicals that cause fluid to leak into surrounding tissues, leading to swelling and inflammation. These areas then attract phagocytes to destroy the invaders.
In addition to defending against immediate threats, the immune system also enhances long-term immunity over time by using that information to recognize invaders in the future. When a threat returns, the body can quickly deploy the correct antibodies to handle it before it affects more cells.
A healthy immune system successfully fights off about 300 colds and countless other potential infections throughout a lifetime.
However, the immune system doesn’t always work perfectly. In people with autoimmune diseases, the immune system can be “tricked” into attacking perfectly healthy cells.
Immune system disorders can lead to conditions like arthritis, type 1 diabetes, and multiple sclerosis.
Without an immune system, health threats would escalate dangerously, potentially becoming life-threatening. Protect your immune system for a safe and healthy life.
