A guide to the basics of the human immune system


With so much of our news today dominated by the spread of coronavirus, people are more aware than ever of the human immune system – but just how does our in-built protective mechanism work and how can it evolve over time?

The human body’s natural defense system

In many ways, the human immune system could be considered your own personal army tasked with defending you. While it is incredibly complex and far more detailed than could be outlined in just a short article, below is a simple beginner’s guide to the body’s natural defense mechanism against disease:

human immunity system

The basics of the immune system’s defenses: The immune system consists of cells, tissues and organs that have the specific task of trying to prevent potentially-harmful germs like viruses, fungi, bacteria and parasites from entering the body. If the immune system detects anything foreign or malicious in your body, it deploys specific cells to destroy the intruder.

The spread of infections: Unfortunately, many common human activities present a significant risk of spreading contagion. Germs can come from multiple sources – human touch, having sex or even just socializing and breathing-in droplets released when other people cough or sneeze. You could also get infections from shared needles, insect bites or food and water.

Our external defenses: The first and most obvious line of defense is skin, however, the body also has similar blockers covering the eye (the cornea) as well as protective tissues in the lungs, bladder, etc.

self cleaning

Self-cleaning mechanisms: While we all (mostly) wash regularly, the body also has in-built cleaning mechanisms to both protect and clean the body. Sweat, tears and mucus all serve to rid the body of dirt and germs and also contain specific enzymes to kill foreign bacteria.

Antigens: You will have likely heard a lot about antigens in the news recently related to Coronavirus. Antigens are essentially substances which are capable of triggering an immune response. Human Leukocyte Antigens (HLAs) have the effect of tagging your cells, making them easier for the body to distinguish them as being your own. Other foreign antigens can also enter the human body by way of viruses or bacteria.

How the body learns to protect you: Even at birth, the human body has natural protection mechanisms and does a pretty good job of defending you. So-called ‘acquired immunity’ typically comes from the antibodies in a mother’s womb as well as natural defensive responses in a baby’s body and sometimes other antigens like a vaccine. Nonetheless, illness in very young children can cause significant problems as outlined in this excellent feature; Newborn Infection Article – The Malpractice Group. Child infections can cause potentially long-lasting damage to children or, in the worst-case scenario, even cause death.

Natural born killers: The human body contains natural killer cells – a type of white blood cell that is dispatched to attack then kill abnormal cells in the body (e.g. cancer). These cells play a vital role when we first get infected.

Other natural defenses: The body has countless other defenses it can deploy, including:

  • Neutrophils: often considered the first line of attack that works by eating or trapping bacteria to stop them from spreading
  • Phagocytes: tasked with eating foreign invaders
  • Eosinophils: attach themselves to – then destroy – large parasites that are too big to be ingested
  • Lymphocytes: T and B cell lymphocytes work to build and improve your immune system. They are the main reason we only catch chickenpox once

As mentioned earlier, the immune system is incredibly complex and the above is only a short summation of how our bodies work to defend us against disease.

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