The document summarizes key points about cytokines from their definition and properties to classification and functions. Cytokines are cell signaling proteins that mediate cell-cell communication during immune responses. They are classified based on structure and receptors. Cytokines play important roles in health by regulating immunity and inflammation but can also contribute to diseases if dysregulated. Some cytokines like interferons and lymphokines are important immune signaling molecules.

1. Reaccredited with B grade with a CGPA of 2.71 in the second cycle of NAAC
affiliated to manonmanium sundaranar university, tirunelveli.
Post graduate & Research Centre – Department of Microbiology
(government aided)
ACADEMIC YEAR 2021-2022
II SEM CORE: IMMUNUNOLOGY – (ZMBM23)
UNIT – I
CYTOKINES
SUBMITTED BY,
K. RAMKUMAR
REG NO: 20211232516122
I M.SC MICROBIOLOGY
SUBMITTED TO
GUIDE: DR.S.VISWANATHAN
ASSISTANT PROFESSOR AND
HEAD

2. Synopsis
 Introduction
 Definition
 General properties
 Classification of cytokines
 Receptor
 Role in health and disease
 Medical use as drugs
 Lymphokines
 Interferons and their types

3. INTRODUCTION:
 The “Cytokines” is derived from a combination of two Greek words – “cyto”
meaning cell and “kines” meaning movement.
 That is low molecular weight.
 Cytokines are cell signaling molecules that aid cell to cell communication in
immune responses and stimulate the movement of cells towards sites of infection.
 Cytokines are a large group of proteins, peptides or glycoproteins that are secreted
by specific cells of immune system.

4.  Cytokines stimulate or suppress the functional activity of lymphocytes, monocytes,
neutrophils, fibroblast and endothelial cells.
 They are synthesized and released by white blood cells and tissue macrophages.
 200 different human cytokines was have been identified.

5. Definition:
 Cytokines are loose category of small proteins important in cell signalling.
 Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the
cytoplasm.
 Cytokines have been shown to be involved in autocrine, paracrine and endocrine
signalling as immunomodulating agents.

6. Macrophage
Granulocyte
Mast cell
Endothelial cells

7. Macrophage:
A type of white blood cell that surrounds and kills microorganisms, and
removes dead cells.
That helps eliminate foreign substance.
Granulocytes:
type of immune cell that has granules with enzymes. That are released
during infections, allergic reactions, and asthma.
Neutrophils, eosinophils, and basophils are granulocytes.
Fibroblast:
A fibroblast is the most common type of cell found in connective tissue.
Important role in healing wound.

8. Endothelial cells:
The main type of cell found in the inside lining of blood vessels, lymph vessels,
and the heart.
Mast cell:
A type of white blood cell that is found in connective tissues all through the
body, especially under the skin, near blood vessels and lymph vessels, in nerves, and
the lungs and intestines.
Lymphocyte:
A type of white blood cell in the immune system of most vertebrates.
Lymphocytes include natural killer cells, T cells and B cells.

9. General properties:
 Cytokines are produced during immune and inflammatory responses and secretion
of these mediators is transient and closely regulated.
 Cytokine effects are often redundant and these proteins can influence the synthesis
or action of other cytokines.
 Cytokines are small secreted proteins which mediate and regulate immunity,
inflammation and hematopoiesis.
 Cytokines trigger the signal transduction pathway by binding to specific receptors
present on the target cells.

10. Cytokine
Receptor
Target cell
Cytokine producing
cell
Biological
effects
Inducing stimulus

11. Autocrine:
An individual cytokines binds to their specific receptor on the same cell
exhibit “autocrine” action.
Paracrine:
The cytokines binds to the nearby target cell, the action is called “paracrine”.
Endocrine:
In some cases, cytokines may bind to the target cells present in the distant
regions of the body, then it is termed as “endocrine”

12. Autocrine action

13. Classification of cytokines:
Based on Structural:
 a-helix bundle family
- IL-2 subfamily
That is largest family. It contains several non-immunological
cytokines including erythropoietin and thrombopoietin.
- IL-10 subfamily
- Interferon subfamily
 IL-1 family, which includes IL-18.
 The cysteine knot
Including TGF-B1, TGF-B2 and TGF-B3
 IL-17 family

14.  In recent years, the cytokine receptors have come to demand the attention of more
investigators than cytokines themselves.
 A classification of cytokine receptors based on their three-dimensional structure.
- Immunoglobulin superfamily
- Hemopoietic Growth Factor family
- Interferon family, IFN-B and Y
- Tumor necrosis factors family
- Transmembrane helix family
- Interleukin-17 receptor family
Receptors:

15. Role in health and disease:
 Cytokines are involved in several developmental processes during embryonic
development.
 Cytokines are crucial for fighting off infections and in other immune responses.
 They can become dysregulated and pathological in inflammation, trauma, sepsis,
and hemorrhagic stroke.
 Dysregulated cytokine secretion in the aged population can lead to
inflammaging.

16. Medical use as drugs:
 Some cytokines have been developed into protein therapeutics using
recombinant DNA technology.
 Bone morphogenetic protein(BMP)
 Erythropoietin(EPO)
 Interleukin 2 , used to treat cancer
 Interferon alfa, used to treat hepatitis C

17. Lymphokines
 Lymphokines are a subset of cytokines that are produced by a type of immune
cell known as a lymphocyte.
 They are protein mediators typically produced by T cells to direct the immune
system response by signalling between its cells.
 Lymphokines have many roles, including the attraction of other immune cells,
including macrophages and other lymphocytes.
 Lymphokines secreted by the T helper cell include, IL2, IL3, IL4, IL5, IL6,
Interferon-gamma, Granulocyte, macrophage and colony stimulating factor.

18. Interferons
 That are group of signalling proteins, that made and released by host cells in
response to the presence of several viruses.
 A virus infected cell will release interferons causing nearby cells to heighten their
anti-viral defenses.
 IFNs belong to the large class of proteins known as cytokines.
 Interferons are named for their ability to “Interfere” with viral replication by
protecting cells from virus infections.

19. Types
 Interferon type I
 Interferon type II
 Interferon type III
 Interferons type I and II are responsible for regulating and activating the immune
response.