The immune system is the human being’s natural defence system and it protects our health throughout our lives. By means of various barriers, it guards the body against penetration by pathogenic microbes and, should they make their way into the system, it then fights the infection.
Innate, or non-specific, immunity is congenital by nature, which means that we are born with it. It constitutes the first line of defence against threats and acts autonomously, recognising a danger with lightning speed and reacting immediately. A person deprived of acquired immunity from birth is capable of surviving for around thirty years, while a foetus without innate immunity will die in utero, in other words, in the internal environment of the womb.
Acquired, or specific, immunity develops throughout our lives. The body learns to recognise various microorganisms, after which it remembers them. As a result, repeated reaction to a given agent is far quicker. On average, the total number of lymphocytes capable of discerning such substances is just a few thousand. This small section of the body’s cells is charged with travelling through approximately one hundred thousand kilometres of blood vessels in the course of some dozen or so hours and spotting any foreign agents which have penetrated the body. In comparison to microbes, lymphocytes are microscopic. If the human body were magnified to the size of Earth, they would be barely the size of two large lorries.
For the hundreds of thousands of years of human evolution, people lived in a dirty environment teeming with viruses and bacteria against which their immune system had to protect them. This intensive ‘training’ gave rise to its natural strengthening and constant readiness to react to new threats. When disinfectants, soap and antibiotics appeared, our living environment became more ‘sterile’ and thus our immune system was no longer exposed to as much grime as before. The upshot of this ‘lack of training’ is that it has become lazy, which has led to its greater susceptibility to various threats. With its equilibrium thrown out of kilter, the immune system often reacts to harmless compounds such as plant pollens, for example, which leads to allergies. The tendency to eat meals which are high in calories but low in nutrients throws the immune system out of balance.