31 Jul

Cytokines and Chemokines

Cyto- comes from the Greek kýtos, meaning “container,” “receptacle,” “body.”and kines as in kinetics or movement. So cytokines are chemical messengers moving between cells acting on receptors. 

Cytokines are a large category of small proteins involved in cell signaling.  

  • Cytokines are peptides and cannot cross the lipid bilayer of cells           
  •  Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents.                                
  • Their definite distinction from hormones is still part of ongoing research.

Cytokines are classified currently by these families by abbreviation

  1. Interleukins (IL)      
  2. Colony-stimulating factors (CSFs)  
  3. Interferons (IFN)
  4. Chemokines (CC)        
  5. Transforming growth factors (TGF)  
  6. Tumour necrosis factor (TNF) families.

Cytokines act through cell receptors on cell surfaces of which there are many that look like this:

Actions of cytokines are either pro-inflammatory - stimulate the immune system or anti-inflammatory suppressing the immune system cells. 

Cytokines of relevance in COVID-19 are thought to be mainly IL-6 (interleukin-6) and some of these are detailed below.

-inflammatory cytokines in COVID-19 (Feb21)

Some research on the roles of IL-1β, IL-6, IL-8, IL-17 and TNFα in COVID-19

Cytokine Profiles and Disease Severity in COVID-19

A Study evaluating the serum levels of interferon (IFN)-γ, interleukin (IL)-5, IL-8, Il-9, IL-17, TGF-β and IFN-γ

For further reading on cytokines - sciencedirect 

Chemokines are tiny protein molecules that form a subfamily of the cell signalling molecules or cytokines. These tiny proteins are secreted by cells to induce chemotaxis in nearby cells. 

Chemokines (from Ancient Greek χῠμείᾱ (khumeíā) 'alchemy', and κῑ́νησῐς (kī́nēsis) 'movement'), or chemotactic cytokines, are a family of small cytokines or signaling proteins secreted by cells that induce directional movement of leukocytes, as well as other cell types, including endothelial and epithelial cells. 

In addition to playing a major role in the activation of host immune responses, chemokines are important for biological processes, including morphogenesis and wound healing, as well as in the pathogenesis of diseases like cancers. Some chemokines are considered pro-inflammatory and can be induced during an immune response to recruit cells of the immune system to a site of infection, while others are considered homeostatic and are involved in controlling the migration of cells during normal processes of tissue maintenance or development

Chemokines are found in all vertebrates, some viruses and some bacteria, but none have been found in other invertebrates.Chemokines have been classified into four main subfamilies: CXC, CC, CX3C and C. 

All of these proteins exert their biological effects by interacting with G protein-linked transmembrane receptors called chemokine receptors, that are selectively found on the surfaces of their target cells

Detailed below some of the different chemokines in other viruses


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