Cytokines: what they are, what types are there and what functions they have

You’ve probably heard of cytokines. But, what are they exactly? What are they for? Who makes them? What biological meaning do they have?

We could say that cytokines are basically like the messengers in our body, which serve to transmit messages between our cells when they have to perform a specific function.

    What are cytokines

    Cytokines (also called cytokines) are proteins that generate cells and work by sending signals between different types of cells, Depending on what our body needs.

    In this article, we will talk about cytokines and their biochemistry, their properties, to whom they send messages, what can be their functions in the body and finally what types exist.

    What are they for?

    As we have already mentioned, cytokines are proteins that cells make when they want to communicate with each other. These low molecular weight proteins act through complex interactions between different types of cells.

    These proteins are part of the immune system and their function is as follows: imagine a small molecule, which is produced by a cell which receives a stimulus.

    this molecule he goes to his receiver (who is in another cell) to give a signal or a message (These receptors are found in cell membranes). This second cell will give a response, and from there an intracellular signal transduction cascade begins. This cascade will trigger a specific biological response.

      Characteristics of cytokines

      cytokines they are very different molecules from each other and very complex, although they share a number of characteristics which we will see in detail below.

      As part of the immune system, are mainly produced by macrophages, essential molecules of the innate immune system. Remember, the innate immune system is what involves cells generically recognizing pathogens and attacking them.

      If we are talking about a specific immune system, the collaborating T cells are responsible for the production of cytokines. The specific immune system is the one which, as its name suggests, has a specificity; that is, cells specifically attack specific pathogenic receptors.

      The production of cytokines is relatively short (Transient) and is subject to the duration of the stimulus (i.e. the pathogen in case of macrophages and T cells)

      Other features include:

      • They possess pleiotropy; that is, they trigger multiple effects after acting on different cells.
      • They are redundant, which means that different cytokines can produce the same effect.
      • They can be synergistic; that is to say, they cause an effect which is potentiated between them.
      • They can be antagonistic; that is, they can block each other.
      • Cytokines have various affinities for their specific receptor.


      There are several classifications of cytokines, because they are very complex molecules, With different origins and different functions. Here we show you different classifications:

      1. According to cytokine interactions

      Basically, interactions happen between lymphoid cells (cells of the immune system), inflammatory cells and hematopoietic cells (Blood cells).

      But these interactions can be of different types, and depending on these types, we get a classification of cytokines:

      1. 1. Autocrine cytokines

      It is these cytokines that they act on the same cell that produces them.

      1. 2. Paracrine cytokines

      It is these cytokines that act in the region adjacent to the secretion site.

      1. 3. Endocrine cytokines

      It is these cytokines that they work in remote areas from where they were secreted. These cytokines travel in the blood and their function is to act on different tissues.

      2. According to the functions of cytokines

      Cytokines, being such diverse and complex molecules, they can fulfill a wide variety of functions. Here we will categorize them into the most essential:

      2. 1. Pro-inflammatory function

      They are pro-inflammatory cytokines; they act on the innate immune response, Nonspecific or inflammation.

      2. 2. Developmental function, cell maturation and / or cytotoxicity

      They act at different times in the cell cycle to model cell development, maturation and / or death.

      2. 3. Production of the functions of different immunoglobulins

      These are the proteins that protect us from infections.

      2. 4. Hematopoietic functions

      It is these cytokines involved in the development and maturation of blood cells (Mostly red blood cells, white blood cells and platelets).

      Cytokine receptors

      As we have seen, cytokines must interact with a receptor in a cell to trigger a response.

      There is a wide variety of cytokine receptors. It is these receptors that will determine the response that will trigger the effector cell. This variety of receptors is grouped into the five so-called cytokine receptor families.

      1. Immunoglobulin superfamily

      These are the known antibody receptors, which are the essential molecules that the body creates to specifically attack pathogens.

      2. Class I family of cytokine receptors

      This family of receptors constitutes the hematopoietin receptors, that is to say blood cells.

      3. Class II cytokine receptor family

      This family of receivers constitutes the interferon receptors. Remember that interferons are proteins made by the body in response to pathogens (viruses, bacteria, parasites, etc.).

      4. TNF receptor family (tumor necrosis factor)

      These are the molecules involved in the processes of inflammation and cell death.

      5. Chemokine receptor family

      This last group of cytokine receptors is particularly peculiar: they are so called because they are able to attract and direct other cells of the immune system to repair tissue.


      Of all these “superfamilies” mentioned, there are several subgroups of each. That is, for example, there are many receptors of TNF which are named TNF-ɑ and TNF-various, various types of receptors of the class I, class II family, etc.

      Each superfamily, as we have seen, is involved in specific molecular mechanisms.

      The most famous cytokines

      Of all the cytokines the body can produce, interleukins (IL) are among the most important cytokines. These types of cytokines are mainly produced by lymphocytes and macrophages, but can also be produced by endothelial cells, fat cells, endothelial cells, muscle cells, etc.

      Its main action is to regulate inflammation by various mechanisms. They are generally classified as pro-inflammatory and anti-inflammatory.

      The other cytokines, also essential for the inflammatory response, are tumor necrosis factor Alpha (TNF-α) and interferons. All these pro-inflammatory proteins.

      As you can see, the body is a complex system where many needs are orchestrated and measured by cytokines so that the body can function through a stimulation-response mechanism.

      Bibliographical references:

      • Feduchi Canosa, Elena (2014). Biochemistry. Essential concepts. Editorial Médica Panamericana SA; second edition.
      • Nelson, David L, Cox, MICHAEL M. (authors), Knife Foix, Claudi M. (translator). (2018). Principles of biochemistry. Lehninger Editorial; seventh edition.
      • Tortora, Gerard J., Derrickson, Bryan (2018). Principles of anatomy and physiology. Editorial Médica Panamericana SA; fifteenth edition.

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