Interleukins and their most important types


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Today we know that any small alteration in a protein in our body can trigger a series of conditions that can lead to serious health problems in the future. Proof of this are the interleukins (or interleukins), proteins that can be found altered in some very rare diseases.

Finding these abnormalities and diagnosing them early is key for doctors to begin treatment appropriate to the disease and the patient’s specific needs. Observing the behaviour of certain proteins can serve as indicators of an irregularity in the correct functioning of the organism. So, in today’s post we are going to talk about interleukins, what types there are and what their analysis can mean.

What are interleukins?

Interleukins are a type of protein made by leukocytes and other cells in the body. These proteins are themselves a group of cytokines and therefore play an immunological role.

The function of interleukins is cell-to-cell communication. They function as messengers between different leukocyte subpopulations and are therefore also involved in the immune system response. They are, in fact, the main means of intracellular communication when microbial invasion occurs. They are responsible for initiating an inflammatory response and defining the magnitude and nature of the specific immune response. They occur during the activation of innate and acquired immunity.

In short, in addition to the important function of cell-to-cell communication, growth, differentiation and motility, interleukins are also responsible for immune functions, such as regulating responses (inflammation). Today we know of a total of 33 types, completely different from each other. Some of these are benign, but others can be indicate processes harmful to the organism.

Interleukin, like other proteins of the cytokine family, is not stored inside cells, but is rapidly and briefly secreted in response to stimuli. Let’s take an example of an infection to see how these proteins would act:

  • The body produces interleukins in response to infection. These are transferred to the target cell (the target).
  • Once they reach their destination, a receptor (a molecule on the surface of the cell) causes them to bind to the cell.
  • The interaction triggers a signalling cascade in the target cell that ultimately alters its behaviour.

Interleukins were first identified in the 1970s. At the time, scientists thought that it was the lecocytes that produced this protein and that it only acted on them. Hence they were christened inter-leukins (‘between leukocytes’). It is true that leukocytes are involved in the immune response. Interleukin was therefore thought to function only as a modulator of immune mechanisms. Although this protein does have this function, research to date has shown that it is also produced by other cells and is involved in other physiological mechanisms.

The functions of interleukins are many, including activating the endothelium, increasing vascular permeability (facilitating the movement of immune cells from the bloodstream into tissue), promoting antibody secretion and controlling the T-cell response.

Types of interleukins

We have already mentioned that some interleukins have pro-inflammatory and some have anti-inflammatory functions. As a cytokine, this protein is able to communicate with cells, recruiting or inhibiting the functions of specific cells (such as dendritic cells), regulating cell proliferation and differentiation, activating or inhibiting the expression of certain genes, etc. Being able to communicate to other cells that there is ‘a problem’ can, in turn, generate an innate or adaptive response. Cytokines are ultimately the basis of the immune response.

There are, as mentioned above, 33 types of interleukins known to date. The most important of these are explained below:

Interleukin-1. It is a polypeptide of which there are two forms (IL-1 and IL-1ß) with a homology of only 26%. These 2 cytokines act on the same receptor, for which the IL-1 receptor antagonist (IL-1ra) also competes. This substance will prevent IL-1 from acting. It generally acts intracellularly and is not found in the general circulation except in cases of severe disease. IL-1ß, on the other hand, is the predominant form in the extracellular space. Activated macrophages are the main physiological source of IL-1, which is notable for its pro-inflammatory capacity.

Interleukin – 2. It acts by promoting T-cell proliferation. Activated T-lymphocytes are generally responsible for producing it, as part of the Th1-type response. It carries out its biological action via a membrane receptor, consisting of three ß-subunits. When the lymphocyte is activated, the subunit or p55 is released into the serum as a soluble receptor. Certain levels of the soluble IL-2 receptor are present in a healthy person, whereas higher than normal levels may be observed in a sick individual. This reflects excessive lymphocyte activation.

Interleukin-3. It is mainly produced by T-lymphocytes and is involved in the early stages of haematopoiesis. Promotes the growth and differentiation of haematopoietic precursor cells. This is why interleukin-3 is also known as ‘multi-CSF’.

Interleukin – 4. It also originates from activated T-lymphocytes and acts preferentially by promoting the activation, proliferation and differentiation of B-lymphocytes. It is involved in the induction of Th2 cells (regulating humoral immunity).

Interleukin – 5. Produced by activated T-lymphocytes, it acts as a stimulatory factor for B-lymphocyte activation, growth and differentiation. It is the main regulatory factor for eosinophilia. Lung cancer and other tumours often cause it.

Interleukin-6. It originates from various cell types. Macrophages, monocytes, fibroblasts and endothelial cells are prominent. It regulates the immune response in haematopoiesis and has pro-inflammatory and anti-inflammatory effects. It produces its biological effects through a membrane receptor composed of two R-IL-6 subunits and gp 130. These 2 receptors are solubilised when they have bound to IL-6. However, while sR-IL-6 acts as an IL-6 agonist, soluble gp 130 antagonises IL-6 action.

Interleukin – 7. It acts by stimulating the development of B- and T-lymphocyte precursor cells. It also has anti-tumour activity by increasing the production of cytotoxic T-lymphocytes and NK cells.

Interleukin – 8. Acts as a chemotactic factor for leukocytes (especially neutrophils). It also promotes their degranulation and stimulates phagocytosis. It should be included in the group of chemokines, which are involved in inflammation, inducing chemotaxis and cell activation of numerous cells involved in inflammatory processes.

Interleukin-9. It is a glycoprotein with mitogenic capacity and capable of inducing T-cell proliferation. It may be involved in the development of T-cell tumours.

Interleukin – 10. inhibit the synthesis of IFN and IL-2 by them. It is the main anti-inflammatory cytokine and acts by inhibiting the synthesis of IL-1, IL-6 and TNF by macrophages.

Interleukin – 11. This protein is produced by bone marrow stromal cells and mesenchymal cells. It is related to other substances in the cytokine group including IL-6, leukaemia inhibitory factor (LIF), oncostatin-M (OSM) and ciliary neurotrophic factor (CNTF). They are characterised by the use of the gp 130 transducer. IL-11 acts on haematopoietic cells, liver cells (inducing acute phase proteins) and intestinal epithelial cells. It acts on them by mediating their protection and regeneration. Unlike IL-6, it has little effect on lymphocytes.

Interleukin – 12. This 70 kDa glycoprotein acts on Th1 T cells and induces IFN and IL-2 synthesis. It is also able to reduce the production of IL-4, IL-5 and IL-10 by Th2 cells.

Interleukin – 13. Regulates monocyte and B-cell function. Decreases production of pro-inflammatory interleukins and chemokines and increases production of IL-1-RA.

Interleukin-14. Designates high molecular weight B-cell growth factor (HMW-BCGF).

Interleukin – 15. It has a similar biological activity to IL-2, but does not act on the same cells. uses the ß-receptors (p75) and (p64) of the IL-2 receptor system as transduction units.

Interleukin-16. It is a pro-inflammatory cytokine secreted by activated CD8 cells. Promotes chemotaxis and expression of IL-2 receptor and HLA-DR.

Interleukin – 17. It is a 155 amino acid glycoprotein produced by CD4 T cells.+ stimulated. It increases the expression of ICAM-1 in fibroblasts and is able to stimulate the secretion of IL-6, IL-8 and G-CSF by epithelial cells, endothelial cells and fibroblasts.

Interleukin – 18. This cytokine induces IFN synthesis. It has a synergistic effect with IL-12 on IFN production by T cells. This protein increases IL-2 production and IL-2 receptor chain expression. It is involved in the regulation of the Th1-type response and may also decrease IL-10 production.


The main function of these cytokines is to communicate between cells. Failure in this regard may result in the message not reaching all the necessary parts and therefore a part of the body not knowing that it is facing danger. Therefore, an analysis of these proteins helps to detect any abnormalities. At AmbarLab we have more than 3000 laboratory tests at your disposal. We are proud to say that our team of specialists will know how to meet your specific needs, so if you have any queries please do not hesitate to contact us.

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