Interleukin & Receptor Proteins

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Interleukin & Receptor Proteins

Interleukin & Receptor Proteins Background

Interleukinin(IL) is a kind of cytokine produced by and used in many kinds of cells. Since it was first discovered that white blood cells are produced and play a regulatory role between cells, hence the name. IL now refers to a class of cytokines whose molecular structure and biological functions have been basically defined and whose important regulatory functions have been uniformly named. IL plays an important role in transmitting information, activating and regulating immune cells, mediating the activation, proliferation and differentiation of T and B cells and playing an important role in inflammatory response. It is a member of the 1ymphokins family, produced by lymphocytes and macrophages.

During the study of the immune response, researchers found that there were many bioactive molecules in the supernatant of cell culture treated with various stimuli, and named them after the measured activity. Nearly 100 factors have been reported in the past ten years. Later, comparative studies with the help of molecular biology techniques found that many factors named after biological activity in the past are actually the same substance capable of exerting multiple biological effects.

Schematic diagram of interleukin 7 and its receptor Fig.1 Schematic diagram of interleukin 7 and its receptor

The classification of interleukins

Classification Character Principle members
Interleukin-1 family (IL-1F) There are 11 members in total, most of which are pro-inflammatory cytokines, which mainly stimulate the expression of genes related to inflammation and autoimmune diseases to induce the expression of effector proteins such as cyclinase 2, phospholipase A2, nitric oxide synthase, interferon receptor and adhesion molecule. It plays an important role in immune regulation and inflammation. IL-1α, IL-1β, IL-Ⅰreceptor antagoni, IL-18, IL-36α, IL-37, IL-36β, IL-36γ, IL-38 and IL-33.
Interleukin-2 family (γc family) There are five of them, and they're a group of cytokines that depend on the γc chain for signaling. IL-2, IL-4, IL-13, IL-15 and IL-21
A family of chemokines IL-3, IL-8 and some cytokines that do not belong to interleukin are classified as chemokines, and IL-8 belongs to its C-X-C/α family. IL-3, IL-8
The interleukin-12 / interleukin-6 family The interleukin-12 / interleukin-6 family consists of five members. IL-6, IL-12, IL-23, IL-27(IL-30), IL-35
The interleukin-10 family IL - 10 family cytokines is Ⅱ class of a family, the immune system plays a variety of regulatory role. IL-10, IL-9, IL-20, IL-22 and IL-24/MDA-7, IL-26.
The interleukin-17 family The interleukin-17 family have IL-17A ~IL-17F IL-17 and IL-25(IL-17E)
Others The rest of the interleukins are not clear which family they belong to IL-5, IL-7, IL-9, IL-11, IL-14, IL-16, IL-31, IL-32

 

  1. Interleukin-2 (IL-2)

    As an important immune regulator, IL - 2 can promote the activation and proliferation of T cells, the growth and differentiation of B cells, and enhance the division and proliferation of NK cells and monocytes. It can also promote the secretion of other cytokines, such as IFN, and enhance the antigen presentation. Therefore, it is an important factor to regulate the body immunity, and plays an important role in anti-tumor, antitoxin, immune regulation and the treatment of infectious diseases.

    IL-2 is produced mainly by T lymphocytes or T lymphocyte lines. Morgan et al. (1976) first found that mouse IL-2 can promote and maintain the growth of T cells in the supernatant of pha-stimulated mouse spleen lymphocyte culture, so it was called T cell growth factor (TCGF). In 1979, it was officially named IL-2 at the second international lymphoid conference.

    IL-2 is a Thl cytokine that can activate macrophages and participate in the occurrence and development of cell-mediated immune responses. The recombinant ch IL-2 gene encoded by poxvirus can express the biologically active ch IL-2 (rFPV—IL-2) in vitro, and selectively increase the expression of IL-8 and IL-2 to activate neutrophils and better play the role of innate effector cells in fighting bacterial growth.

    In infectious bursal disease virus (IBDV)(Park et al. 2009) during vaccine immunization, IL-2 was used simultaneously, and the results showed a significant increase in protective immunity. It indicates that ch IL-2 has the function of adjuvant. At present, the functional domain of ch IL-2 has been identified. This helps to explain the interaction between ch IL-2 and its receptor, and thus elucidates the mechanism for the existence of a potential vaccine in the chicken immune system.

    Molecular structure and coding genes of IL-2: IL-2 is a glycoprotein with 133 amino acid residues and a relative molecular weight of (15 ~ 35)×103. Natural IL-2 contains glycosyl at the N end, but the glycosyl has no significant effect on the biological activity of IL-2. IL-2 molecule contains three cysteine amino acids, located at positions 58, 105 and 125, respectively. Among them, the intra-chain disulfide bond formed between 58 and 105 cysteine plays an important role in maintaining the biological activity of IL-2.

    Schematic diagram of interleukin-2 protein Fig.2 Schematic diagram of interleukin-2 protein
  2. Interleukin-3 (IL-3)

    The human interleukin 3 (IL-3) gene is located on chromosome 5q23~31, with a relative molecular weight of 15kD and composed of 133 amino acids. IL-3 is mainly produced by activated CD4+T cells. Its main biological function is to promote the directed differentiation and proliferation of pluripotent hematopoietic stem cells in the bone marrow and produce various types of blood cells.

  3. Interleukin-4 (IL-4)

    The human interleukin-4 (IL-4) gene is located on chromosome 5 with a relative molecular weight of 20kD and is composed of 129 amino acids. IL-4 is mainly produced by activated T cells, monocytes, mast cells and basophils. Its main biological functions are to promote the activation, proliferation, differentiation, secretion of Ig, IgE type immunoglobulin conversion, and inhibition of Thl cells.

  4. Interleukin-5 (IL-5)

    IL-5, mainly produced by activated T cells, promotes IgA synthesis and IgM secretion. Physiological effects: chemotactic human eosinophils, prolonging the survival time of mature eosinophils, stimulating the function of human and mouse eosinophils, and inducing eosinophils differentiation.

  5. Interleukin-6 (IL-6)

    IL-6 is produced in lymphoid and some non-lymphoid cells. Physiological effects: IL-6 can promote the proliferation and differentiation of various cells, which is related to the occurrence of various clinical diseases.

    A hypothesized model of the involvement of IL-6 from different cell sources in the pathogenesis of HDM induced allergic asthma Fig.3 A hypothesized model of the involvement of IL-6 from different cell sources in the pathogenesis of HDM induced allergic asthma
    IL-6 drives the pathway involved in allergen-induced asthma pathogenesis Fig.4 IL-6 drives the pathway involved in allergen-induced asthma pathogenesis
  6. Interleukin-7 (IL-7)

    Human interleukin-7 (IL-7) gene is located on chromosome 8q12~13, with a relative molecular weight of 25kD and composed of 152 amino acids. IL-7 is mainly produced by bone marrow stromal cells and its main biological function is to promote the proliferation and differentiation of precursor cells of T and B cells.

  7. Interleukin-8 (IL-8)

    IL-8 is a neutrophil chemokine produced by monocytes. Physiological effects: chemotaxis and activation of neutrophils, stimulating their production of leukotriene. Chemotaxis of eosinophils and stimulation of their release of histamine may be involved in the development of tachycoid hypersensitivity. In addition, it can also chemotactic T lymphocytes, cell proliferation and differentiation and immune regulation.

  8. Interleukin-9 (IL-9)

    Human interleukin-9 (IL-9) gene is located on chromosome 5 with a relative molecular weight of 30-40kd and composed of 126 amino acids. IL-9 is produced by Th cells and its main biological function is to stimulate the growth of Th2 cells and mast cells.

  9. Interleukin-10 (IL-10)

    Human interleukin-10 (IL-10) gene is located in chromosome lq31~32, with a relative molecular weight of 18kD and composed of 160 amino acids. IL-10 is mainly produced by Th2 cells, and its main biological function is to inhibit the production of IL-2 and IFN-1 by Thl cells and to inhibit the activity of macrophages.

  10. Interleukin-11 (IL-11)

    The human interleukin-11 (IL -11) gene is located in chromosome 19q13~14, with a relative molecular weight of 23kD and composed of 178 amino acids. IL-11 can be produced by bone marrow stromal cells. Its main biological functions are to synergistically stimulate hematopoiesis, enhance the production of T cells and monocytes dependent B cell antibodies, and stimulate the expression of acute phase proteins in liver cells.

Conclusion

There are many kinds of interleukins, and new interleukins are still being discovered. In terms of molecular structure, interleukins are small peptides, most of which are composed of about 100 amino acids. Interleukinin exerts its biological effects by specific binding to cytokine receptors on the surface of target cells. These effects include promoting the proliferation and differentiation of target cells, enhancing the effect of anti-infection and killing tumor cells, promoting or inhibiting the synthesis of other cytokines, promoting the inflammatory process, and affecting cell metabolism.

Schematic diagram of the strong regulatory effect of IL-36 on dendritic and T cells Fig.5 Schematic diagram of the strong regulatory effect of IL-36 on dendritic and T cells

At present, the detection of interleukin has not been widely carried out in clinical diagnosis, mainly for the following reasons:

  1. Interleukinin has no disease specificity.
  2. The content of interleukin was very low (pg/mL), and there were significant interferences from allotropic antibodies, rheumatoid factors, and specific and non-specific cytokine binding proteins.
  3. The detection method of interleukinin is not perfect, and the results obtained by different detection methods are quite different.

References:

  1. Dinarello C A. Interleukin-1[J]. Reviews of infectious diseases, 1984, 6(1): 51-95.
  2. Dinarello C A. Interleukin-1 and interleukin-1 antagonism[J]. Blood, 1991, 77(8): 1627-1652.
  3. Moore K W, de Waal Malefyt R, Coffman R L, et al. Interleukin-10 and the interleukin-10 receptor[J]. Annual review of immunology, 2001, 19(1): 683-765.
  4. Smith K A. Interleukin 2[J]. Annual review of immunology, 1984, 2(1): 319-333.
  5. Van Snick J. Interleukin-6: an overview[J]. Annual review of immunology, 1990, 8(1): 253-278.
  6. Kishimoto T. The biology of interleukin-6[J]. Blood, 1989, 74(1): 1-10.
  7. de Waal Malefyt R, Hans Y, Roncarolo M G, et al. Interleukin-10[J]. Current opinion in immunology, 1992, 4(3): 314-320.

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