A. Zinc in immune system
Immune system needs zinc essential trace element to fight against infections due to viruses, bacteria, fungi and protozoa (Bonaventura et al., 2015). Zinc-binding proteins, like metallothioneins (MTs) are from intra-cellular metal binding proteins which are present in all living things and they are important for the zinc effect in the immune system (Stefanidou et al., 2006). Without zinc, immune system cannot do their work to ensure that the body is not exposed to any pathogen. It can decrease lytic activity of natural killer cells, damage the natural killer T cell cytotoxicity and immune signalling, affects the neuroendocrine immune pathway and alters cytokine production in mast cells (Muzzioli et al.,2009; Mocchegianietal,2003; article 14). Moreover, zinc is one of the components that is needed in thymic hormones which commands and ease the process of lymphocyte maturation (Bhowmik & Chiranjib, 2010). Basically, eating too little of zinc can impair the immune system making you more likely to get sick.
Sometimes there are other factors to consider that can affect whether or not Zinc requirements are met in the human body. These factors include diet consumed, climatic conditions, and existence of stress due to stress, trauma, parasitic infestations and infections (Stefanidou et al., 2006). When someone is sick with the flu, it is said that the immune system is able to fight the flu virus with the aid of zinc. People in contact with those who have viruses might get infected by them too. When the body is exposed to pathogens, phagocytosis starts to trap and kill them by producing reactive oxygen. This process usually occurs in innate immune system. Low concentration of zinc is means by decrease in phagocytosis process (Bonaventura et al., 2015). Trace elements such as selenium, iron, copper, zinc and copper to zinc ratios could serve as a symptom of viral liver failure (Kaur, Gupta, Saraf, & Saraf, 2014; Science & Medical, 2006).
Innate immune system should begin first and then followed by an adaptive immune system. Adaptive immune system is related to the T lymphocyte and B lymphocyte. T lymphocyte is matured by thymulin with the aid of zinc. Thymulin is a non-apeptidic hormone produced by thymic epithelial cell, (Dardenne, 2002). It was known that after being deprived of zinc for too long, both human or animals are more susceptible to injuries that comes with oxidative stress (Stefanidou et al., 2006). Acrodermatitis enteropathica leads to zinc deficiency in humans and this is an autosomal genetic recessive defect of the zinc metabolism which then affects obstruction of zinc absorption (King, 2000).
Another reason to keep zinc levels in our body to be at a normal level is to prevent creating damaged homeostasis in our system. This is due to the defective platelet aggregation, a decrease in T-Cell number and the responsiveness of T-lymphocytes to phytomitogens (Stefanidou et al., 2006). In terms of ageing, one of the many roots causing immunological responses to decline is because neuroendocrine function in the body system is failing (Mocchegiani et al., 2006; Stefanidou et al., 2006) and increasing in apoptosis regulated by zinc (Stefanidou et al., 2006).
The abnormal occurrence of various infections and the existence of lymphopenia and lymphoid organ atrophy in malnourished children have been observed many times. The evidence gathered had concluded that the reason is due to zinc insufficiency which is then related to this type of immunodeficiency (Dardenne, 2002).
Much more diseases can be developed such as gastrointestinal disorders, renal disease, sickle cell anaemia, alcoholism, some cancer types, AIDS, burns and others (Fraker, King, Laakko, & Vollmer, 2018; Keen, 1990; Mocchegiani & Fabris, 1995; Stefanidou et al., 2006). Appropriate zinc supplementation prescribed to those individuals could help in preventing damage towards their immune system and massively improve the resistance of a host to fight against the infections (Dardenne, 2002).
A. Zinc in immune system