The immune system protects the body against various harmful pathogens, such as bacteria and viruses. There are two main types of immunity: innate immunity and adaptive immunity. Innate immunity is activated immediately when the pathogen is introduced into the body. The response involves cells such as macrophages, leukocytes, natural killer cells, dendritic cells, and the complement system (Deretic & Levine, 2018). The innate immune system also includes barriers to entry of an organism into the body such as the skin. The immune system responds quickly to an infection but is non-specific. To respond better to repeated infections, the body has another type of immunity: adaptive immunity.
Adaptive immunity is usually developed because of exposure to a specific disease-causing organism. Adaptive immunity is composed of T-cells that are responsible for cell-mediated immunity and B-cells that are responsible for humoral immunity (Berry et al., 2020). For example, an infection by the pathogen that causes smallpox enables the body’s B-cells to produce antibodies against that specific pathogen. In case of re-infection by Smallpox, the body is better prepared to quickly respond to the invasion since it has antibodies specific to the pathogen that causes smallpox. Adaptive immunity is also the basis for vaccination as weakened forms of the pathogen or a part of the pathogen are intentionally introduced into the body to produce antibodies against the pathogen.
Stress is a biological response of the body to psychological or physical distress. Stress has both negative and positive effects on the immune system. Short-term stress usually activates the immune system as the body switches to a fight or flight state. There is increased production of cytokines which coordinate various functions of both the innate and adaptive immunity (Dhabhar, 2019). Additionally, short-term stress increases the maturation and transportation of lymphocytes. However, long-term stress is detrimental to the immune system. This is because it leads to an imbalance in Type 1 and types 2 cytokines, which results in a dysregulated innate and adaptive immunity. Moreover, long-term stress may increase the risk of developing some types of tumors by inhibiting the production of type 1 cytokines.
Berry, R., Watson, G. M., Jonjic, S., Degli-Esposti, M. A., & Rossjohn, J. (2020). Modulation of innate and adaptive immunity by cytomegaloviruses. Nature Reviews Immunology, 20(2), 113-127.
Deretic, V., & Levine, B. (2018). Autophagy balances inflammation in innate immunity. Autophagy, 14(2), 243-251.
Dhabhar, F. S. (2019). The power of positive stress–a complementary commentary. Stress, 22(5), 526-529.