What is the Difference Between Cytokines and Interferons

The key difference between cytokines and interferons is that cytokines are small proteins important in cell signalling and controlling the growth and activity of blood cells and other cells in the immune system, and they follow autocrine, paracrine, or endocrine signalling, while interferons (IFNs) are signalling proteins that are made and released by host cells in the presence of viruses and cancer cells and they follow autocrine or paracrine activity.

An immune system is a complex network of cells, proteins, and organs to defend the body against infections while protecting the body’s own cells. The immune system consists of two subsystems: innate immune system and adaptive immune system. Cytokines are released from the innate immune cells, and they play an important role in the regulation of immune responses. They act as the source of regulatory signals that initiate and constrain inflammatory responses against injuries and pathogens. Interferons act as mediators due to their antiviral activity and alert the cellular immune system to viral infections.

CONTENTS

1. Overview and Key Difference
2. What are Cytokines
3. What are Interferons
4. Similarities – Cytokines and Interferons
5. Cytokines vs Interferons in Tabular Form
6. Summary – Cytokines vs Interferons

What are Cytokines?

Cytokines are small proteins that are important in cell signalling and controlling the growth and activity of blood cells and other cells in the immune system. They are peptides and cannot cross the lipid bilayer in order to enter the cytoplasm. They also act as immunomodulating agents by involving autocrine, paracrine, and endocrine signalling. A range of cells, including immune cells such as macrophages, T lymphocytes, B lymphocytes, mast cells, endothelial cells, fibroblasts, and stromal cells release cytokines. They act as cell surface receptors. Cytokines also regulate immune tolerance by affecting T cell activation and differentiation.

A specific type of cytokine known as chemokine helps immune cells move toward a target. Chemokines are of different types: interferons (IFNs), interleukins (ILs), tumour necrosis factors (TNF), and growth factors. Other types of cytokines include granulocyte-macrophage colony-stimulating factor (GM-CSF), leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), thymic stromal lymphopoietin (TSLP), oncostatin M (OSM), cardiotrophin-1 (CT-1) and cardiotrophin-like cytokine factor 1 (CLCF1). IFNs help the body to resist viral infections and cancers. ILs act as chemical signals between white blood cells. TNF aids in cell signalling and is used by the immune system. Growth factors act as chemical messengers that mediate intracellular communication to regulate nuclear and cellular functions.

Cytokines usually act through their receptors to transmit signals for cell survival, proliferation, function, and differentiation. There are six major receptors of cytokines, and they are type I cytokine receptors, type II cytokine receptors, TNF receptors, IL-1 receptors, tyrosine kinase receptors, and chemokine receptors.

What are Interferons?

Interferons (IFNs) are signalling proteins that are made and released by host cells in the presence of viruses and cancer cells. In the presence of a virus or a cancer cell, an infected cell releases IFNs, causing the nearby cells to trigger defense mechanisms. They belong to a class of proteins called cytokines. They usually perform paracrine or autocrine actions.

There are mainly three classes of IFNs depending on the type of receptors through which they signal: type 1 IFN, type 2 IFN, and type 3 IFN. They help in the regulation of the immune system and fight against viral infections. Type 1 IFN is produced by fibroblasts and monocytes when the body recognizes an invasion of a virus. IFN-α, IFN-β, IFN-ε, IFN-κ, and IFN-ω are several types of type 1 IFN in the human body. Type 2 IFN is also known as immune interferon. They are released by cytotoxic T cells and type 1 T helper cells. Type 2 IFNs are activated by interleukin-12 and are present as IFN-γ in the human body. Type 3 IFN signals through a receptor complex that consists of interleukin-10. Interferons generally act as antiviral agents and modulate the functions of the immune system. IFNs also stop cancer cells from growing and dividing further.

What are the Similarities Between Cytokines and Interferons?

• Cytokines and interferons are small proteins.
• They are important in cell signalling and cell activity in the immune system.
• They act through receptors to transmit signals.
• They arise through blood cells.
• Cytokines and interferons belong to both innate and adaptive immune systems.
• Both boost anti-cancer activity.
• Moreover, both cells are produced by macrophages.

What is the Difference Between Cytokines and Interferons?

Cytokines are regulatory proteins that regulate the cells of the immune system, while interferons are a group of proteins that help in preventing viral replications of infected cells. Thus, this is the key difference between cytokines and interferons. Cytokines follow autocrine, paracrine, or endocrine signalling, while interferons follow autocrine or paracrine activity. So, this is another difference between cytokines and interferons. Moreover, cytokines are a large group of signalling molecules, while interferons are a sub-type of cytokines.

The below infographic presents the differences between cytokines and interferons in tabular form for side-by-side comparison.

Summary – Cytokines vs Interferons

Cytokines are small proteins important in cell signalling and controlling the growth and activity of blood cells and other cells in the immune system. Cytokines and interferons belong to innate and adaptive immune systems. Cytokines follow autocrine, paracrine, or endocrine signalling while interferons follow autocrine or paracrine activity. The different types of cytokines are chemokines, interferons, interleukins, lymphokines, tumour necrosis factors, and growth factors. Cytokines affect the growth of all blood cells and other cells that help the immune and inflammation responses. Interferons are signalling proteins that are made and released by host cells in the presence of viruses and cancer cells. They are mainly divided into three classes as type 1 IFN, type 2 IFN and type 3 IFN. Interferons detect viruses, germs, or cancer cells in the body and trigger killer immune cells to fight and prevent replication of the invaders. Thus, this summarizes the difference between cytokines and interferons.

Reference:

1. “Cytokines and Their Side Effects.” American Cancer Society.
2. “Interferon.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Physiopathologie et grade du syndrome de libération des cytokines” By Shimabukuro-Vornhagen, A., Gödel, P., Subklewe, M. et al. Cytokine release syndrome. j. immunotherapy cancer 6, 56 (2018).  (CC BY-SA 4.0) via Commons Wikimedia
2. “Intereferon and cancer cells” By Medrano RFV, Hunger A, Mendonça SA, Barbuto JAM, Strauss BE – Oncotarget. 2017 Jul 25;8(41):71249-71284. Immunomodulatory and antitumor effects of type I interferons and their application in cancer therapy. (CC BY 3.0) via Commons Wikimedia