The immune system is a complex network of cells, tissues, and organs that protect the body from infection. The immune system contains different types of cells classified as either T helper cells or cytotoxic T lymphocytes. Cytokines also play an important role in regulating the immune response in Human IL-2. This article will explore whether cytokines are immune mediators by assessing their functions and how they regulate the body’s response to pathogens.
What Are Cytokines?
A cytokine is a protein that regulates immune response. There are two types of cytokines: proinflammatory and anti-inflammatory. Proinflammatory cytokines regulate inflammation, while anti-inflammatory cytokines help to decrease it.
Role Of Proinflammatory Cytokines
Proinflammatory cytokines aid in the body’s inflammatory response by recruiting leukocytes to fight pathogens within tissues at sites of infection or injury. These cells can also activate endothelial cells that line blood vessel walls, causing them to become more permeable, allowing plasma fluids to move into the surrounding tissue. This process is known as recruitment inflammation because it recruits immune mediators such as macrophages and neutrophils to an infection or injury site.
Role Of Anti-inflammatory Cytokines
Anti-inflammatory cytokines aid in resolving inflammations through mechanisms that contribute toward cell growth, proliferation, differentiation, and survival. Thus, they promote tissue repair while preventing unnecessary tissue damage. They also stimulate the production of interferon which performs two functions:
i) Prevents viruses from infecting cells
ii) Stimulates macrophages and B-cells to produce antibodies that can help fight off an infection or pathogen themselves by recognizing antigens on their surface, and activates the T-cells. Hence, they become more effective in killing infected cells directly and augment the cytotoxic effects of NK cells against tumors by stimulating them to release perforin proteins into surrounding cancerous or virus-infected tissues, which create pores through membranes allowing for antibody fusion with antigens, leading toward apoptosis cell death.
More On Cytokines
The original function of cytokines was to serve as immune mediators between different types of leukocytes, including lymphocytes such as T helper cells that play a role in differentiating whether a pathogen is an allergen or a threat through the secretion of cytokines. However, as time progressed and advancements were made, including vaccinations, it became apparent that various types of immune mediations also occurred between cells other than lymphocytes, such as dendritic cells, which are specialized antigen-presenting cells (APCs). They are found within tissues where they can sample antigens from pathogens during tissue invasion then travel to T cell areas called germinal centers located at secondary lymphoid organs like the spleen and lymph nodes. Here they present these antigens to naïve T helper cells. Hence, their APC receptors bind with them, leading toward differentiation into either cytotoxic CD+ CTLs or memory CD + Th’s depending on stimulation.
How Are Cytokines Secreted And Activated?
Cytokines can be secreted from cells as proteins or messenger molecules called lymphokines, chemokines, and interleukins, which transfer information between cells to coordinate their actions during an immune response. Lymphokine stimulates other white blood cells such as T helper cells and cytotoxic T lymphocytes; chemoattractant causes cell migration towards its source usually because of low levels, and interferon moves outside the body’s boundaries into infected areas.
Cytokines are activated when cells release proteins that have been stored in secretory granules. The cytokine can then attach itself to a receptor on the surface of another cell and pass information between them. Interferon-alpha, for example, interacts with receptors present on T helper cells or macrophages, which will activate protein kinase R (PKR) inside these target cells. PKR is an enzyme responsible for stopping virus replication by destroying mRNA molecules necessary for viral growth and other functions such as cellular metabolism and immune response regulation.
How Cytokines Function
The process of how cytokines function is very complex. It consists of multiple steps involving different cells types as well as the production, release, binding with cellular receptors or antigens on their surface, which can allow them to activate downstream signaling pathways such as autocrine (self), paracrine (nearby), or endocrine (far away) depending on where they are released into surrounding tissues that contain receptor proteins capable of recognizing them allowing for specific effects in those areas only rather than throughout the whole body like hormones do.
Cytokines also bind onto cytokine receptors located on the cell membrane that contain intracellular tails containing intrinsic tyrosine kinase activity or associate themselves into trimetric complexes like IL 12 consisting of p40, gp130, and LIFR beta chains that result in APCs stimulation through autocrine signaling pathways.
Cytokines are involved in immune mediations between cells of the immune system to prevent infection, move towards sites of inflammation or injury, and trigger cell death through apoptosis.