Abstract

The immune system is the defense system that creates the reactions of living things, which are at the level of development and ability to distinguish foreign substances in their hereditary structure, against these substances. These reactions, which are called immune responses, are basically aimed at protecting the macro organism from possible harmful factors. Even physical barriers such as skin and mucous membranes are considered within the scope of the immune system, but almost all of the cells that play a role are members of the hematopoietic system. Immune system cells and their functions can be manipulated, and vaccines, humanity’s greatest victory against diseases, are an example of this manipulation. There is an extremely sensitive setting in the functioning and reactions of the immune system. Deviations from this setting to plus or minus can result in a wide variety of serious, life-threatening conditions. In particular, the fact that the losses experienced during the Coronavirus disease-2019 (COVID-19) pandemic are often the result of an exaggerated reaction of the immune system rather than the direct effect of the virus shows that the functions of the immune system can be very surprising. In this review; The characteristics and functions of the immune system, the production techniques of vaccines and the COVID-19 pandemic and immune system functions are discussed in the light of current literature.