The immune system, from the Latin word immunis, meaning “exempt” (i.e. “exempt from infectious diseases”), can be defined as the body’s defense system, which has the primary function of protecting it from the attack of viruses, bacteria and other harmful microorganisms present in the environment. Despite this apparently simple definition, anatomical and cellular structures as well as biochemical processes with an “anti-pathogen” protective action are among the most complex in the organism, to the extent that only during the past decades researchers have started to fully understand the real functioning of this system.
The immune system, in fact, consists in a dense network of organs, tissues and specific cells scattered across the organism and communicating with each other through the circulatory and lymphatic systems, capable of recognizing harmful exogenous and endogenous structures, that must therefore be eliminated.
According to the modes of recognition regarding antigens it is possible to distinguish two areas in the immune system:
- non-specific or innate immunity: this includes anatomical defensive barriers – physiological, phagocytic and inflammatory;
- specific or adaptive immunity: this includes chemical and cellular mediators responsible for a more powerful and targeted defensive response, capable of recognizing any kind of antigen.
This latter part of the immune system, which is the most effective and efficient, particularly against microbial aggressions, acts mainly through one type of cells: lymphocytes, which differ from each other according to the type of antigen to fight. In particular, if the aggressor is a virus or an intracellular bacterium (tuberculosis, salmonellosis, etc.) a Th1 response will be activated (Type 1 T helper lymphocytes), whereas for infections coming from extracellular bacteria (as in most cases), mycetes or antigenic agents (elements not recognized as “friendly”, such as not completely metabolised food macromolecules), the system puts forward a Th2 response (Type 2 T helper lymphocytes).
In healthy individuals the system (Th1 – Th2) is balanced, so when the aggression occurs it “specializes” in one direction or the other according to the type of microorganisms to be dealt with, and then balance is restored. Problems crop up when the system happens to be unbalanced towards one or the other part. Recent discoveries have shown that subjects with an immune system that is constantly unbalanced towards Th1 have a greater chance of developing autoimmune types of diseases (multiple sclerosis, rheumatoid arthritis, diabetes mellitus, celiac disease, etc.), whereas people whose immune system is unbalanced towards Th2, probably are most likely to suffer from allergies. The meaning of “balance of the immune system” will now be clearer, but what really matters is that the balance of the immune systems has an impact on the individual’s health.
Having a balanced immune system means higher chances of preventing diseases and, in case they do occur, better chances of rapidly overcoming them without any complications.