Human immunity is defined as the ability of the body to resist certain harmful substances such as germs, viruses and other pathogens by utilizing what is known as the immune system, which protects the body against a variety of pathogens.
This system is characterized by a complex composition that includes both qualitative and non-qualitative components; the non-qualitative components act as a barrier or a front line of defense against a wide spectrum of pathogens regardless of their nature, while other components of the immune system adapt to each new disease that is encountered while having the ability to generate a special type of immunity specific to the encountered pathogen.
Non-qualitative components include body fluids such as saliva, tears, acidic gastric secretion, skin and Mucous membranes lining of respiratory, digestive and reproductive systems. These components prevent the pathogen from entering the body, and include macrophages that eliminate the pathogen by swallowing and digestion, and in both cases, the immunity resulting from these components is called natural or innate immunity.
The qualitative components include cells and specialized organs that act selectively to eliminate the pathogen, in case it managed to penetrate the front lines of defense, i.e. the non-qualitative immunological components. The qualitative components include lymphocytes, which are divided into two types, B-cells, And T-cells. These cells produce antibodies that are specialized in each pathogen which results in creating the so-called acquired immunity, which has the advantage of obtaining a memory, where the body can retrieve the immune response in the case of exposure to the same pathogen again, unlike the innate immunity, which is characterized as an instant system which does not have an immune memory.