Cytokines are proteins secreted by immune cells that mediate their functions and are produced in response to antigens, playing a critical role in cell growth, differentiation, and immune responses. They act primarily over short distances and time spans, binding to specific membrane receptors to induce gene expression, often in a cascade manner. Cytokines demonstrate various functional properties including synergy, redundancy, and pleiotropism, and are predominantly produced by helper T cells and macrophages.

1. LESSON 8
CYTOKINES

2. Properties of cytokines
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Cytokines are proteins secreted by;
Cells of innate and adaptive immunity
Cytokines mediate the functions of these cells.
Produced in response to microbes and other
antigens.

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Functions of cytokines include;
Stimulate the growth and differentiation of
lymphocytes.
Stimulate the development of hematopoietic
cells.
Therapeutic agents-target for specific
antagonists in immune and inflammatory
diseases.

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Cytokines are named based on their cellular
source.
Monokines-produced by monocytes
Lymphokines- produced by lymphocytes.
Generally called cytokines because they are
produced by many other cells.

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Because many cytokines are made by
leukocytes and act on other leukocytes are
also called interleukins.
(1)The family of cytokines consists mainly of
smaller, water-soluble proteins and
glycoproteins with.
(2) Generally (although not always) they act
over short distances and short time spans.

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(3) They act by binding to specific membrane
receptors, and induce specific gene expression
via a second messenger (often tyrosine kinases)
.
(4) Cytokines are often produced in a cascade,
as one cytokine stimulates its target cells to
secret additional cytokines.

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(5) Cytokines can act "synergistically" (two or
more cytokines acting together) or "
antagonistically" (causing opposing activities).
(6) Certain cytokines are "redundant" in their
activity, (means similar functions can be
stimulated by different cytokines)

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(7) Cytokines express "pleiotropism" (literally
means a single cytokine has many different
functional effects on many different cell types,
but in fact sometimes even on the same cell).
(8) They act at very low concentrations and
possess very short life span.
(9) They are produced de novo in response to
an immune stimulus.

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(10) Responses to cytokines include
increasing or decreasing expression of
membrane proteins (including cytokine
receptors), proliferation, and secretion of
effectors molecules.
(11) Cytokines are released by many cell
populations, but the predominant producers
are helper T cells (TH) and macrophages.