Immunosero Mod 2.2

Cytokine

opolypeptides produced in response to microbes and other antigens that mediate

and regulate immune and inflammatory reactions.

ochemical messengers that regulate immunity, influencing both the innate and

adaptive responses to infection.

o CHONs secreted by WBCs that transmit messages to regulate cell growth and

differentiation.

Lymphokine

produced by lymphocytes

Monokine

– produced by monocytes

Pleiotropic

Redundancy

Action of cytokines are often

Autocrine

bind to receptors on the same cell from which they were secreted are said to signal in an

Paracrine

act on cells within the tissue region surrounding their cellular source

Endocrine

✓diffuse into the bloodstream, allowing them to influence cells far from the cell or cells that produce them.

✓act as hormones

Synergistic

two different cytokines complement and enhance each other

Antagonism

one cytokine counteracts the action of another

Cytokine cascade

Many cytokines induce the production of additional cytokines by target cells, resulting in a

Tumor Necrosis Factors (TNF)

Interferons (IFN)

Transforming Growth Factors (TGF)

Chemokines

Interleukins (IL)

Major Cytokine Family

Cytokines in the Innate Immune Response

• Produced mainly by mononuclear phagocytes

• Mostly acts on endothelial cells and leukocytes to stimulate the early inflammatory reactions to microbes

Cytokines in the Adaptive Immune Response

Produced mainly by T lymphocytes in response to foreign antigens

Hematopoietic Growth Factors

• Produced by bone marrow stromal cells, leukocytes and other cells

• Stimulate the growth and differentiation of immature leukocytes

✓interleukin-1 (IL-1)

✓interleukin-6 (IL-6)

✓TNF-α

Primary cytokines provoked by infection with extracellular microbes

The Interleukin-1 (IL-1) Cytokine Family

family of 11 structurally and functionally related cytokines

✓IL-1ɑ

✓IL-1β

✓IL-1RA (IL-1eceptor antagonist)

The Interleukin-1 (IL-1) Cytokine Family is characterized by

IL-1α

• expressed in;

✓phagocytic cells, epithelial cells from

the skin, lungs, gastrointestinal tract

• retained within the cell cytoplasm

and is only released after cell

death.

free IL-1α

✓helps to attract inflammatory cells to areas where cells and tissues are being damaged or killed

• released from macrophages and monocytes

• mediates paracrine and endocrine activity

✓ activation of phagocytes, fever, and production of acute-phase proteins

Chemokines

binding of IL-1β to IL-1 receptors on blood vessel endothelial cells alters adhesion molecule expression and stimulates the production o

IL-1β

endogenous pyrogen: has an ability to induce fever

nduces the production of specific Colony Stimulating Factors in the bone marrow

IL-1RA

• Anti-inflammatory:

✓antagonizes, or works against, the activity of other IL-1 cytokines

• accomplishes this antagonism by binding to only one of the

two transmembrane proteins that compose the IL-1

receptor.

• IL-1RA helps to regulate the physiological response to IL-1

and turn off the response when no longer needed.

Tumor Necrosis Factors (TNF)

products of macrophages and lymphocytes. • The name tumor necrosis factor emerged from the observation that these cytokines induce lysis of mouse tumor cells.

✓TNF-α aka cachectin

✓TNF-β aka lymphotoxin

Subpopulations of TNF

cachectin

✓TNF-α aka

lymphotoxin

✓TNF-β aka

TNF-α

• produced by macrophages

• Major inducer: Lipopolysaccharide (LPS), a component of the cell walls of gram-negative bacteria

TNFR1
TNFR2

TNF-α is a ligand for two receptors:

TNFR!

TNF-α

expressed on many cells and tissues throughout the body

TNFR2

TNF-α

limited to cells of hematopoietic origin and endothelial cells

TNF-β

• aka lymphotoxin

✓causes cell death, or cytotoxicity, in many different types of cells.

• produced by a unique class of lymphocytes known as lymphoidtissue inducer cells

✓important signal during the development of lymphoid tissues in the

gastrointestinal immune system, anti-parasitic

• necessary for the formation of secondary lymphoid tissues

(mesenteric lymph nodes and Peyer’s patches)

lymphoid-tissue inducer cell

TNF-β produced by a unique class of lymphocytes known as

lymphoid-tissue inducer cell

✓important signal during the development of lymphoid tissues in the gastrointestinal immune system, anti-parasitic

Interleukin-6 (IL-6)

third cytokine most prominently associated with the inflammatory response

✓macrophages/monocytes

✓endothelial cells

✓fibroblasts

✓some varieties of lymphocytes

✓skeletal muscle cells

✓adipose tissue

pricipal cell sources of Interleukin-6 (IL-6)

IL-6 as innate cytokine

✓ stimulates the production of acute-phase proteins by liver hepatocytes

✓ increases the production and release of granulocytes by the bone marrow.

✓ stimulates the production of chemokines

IL-6 as adaptive cytokine

✓ increases the activation of B and T lymphocytes

✓ modulates immunoglobulin synthesis

✓ induces CD4+ T cells to produce greater quantities of both pro- and anti-inflammatory cytokines

• IL-6 receptor(IL-6R) – IL6Rα or CD126

• growth factors, called glycoprotein 130 (gp130)

IL-6 multiple subunits

growth factors, called glycoprotein 130 (gp130)

✓initiate intracellular signaling cascades, driving the expression of IL-6-mediated genes that code for products such as C-reactive protein, complement proteins, and fibrinogen

Chemokines

derived from the words cytokine and chemotaxis (movement of a cell toward a stimulus)-chemoattractants.

subgroup of cytokines that influence the motility and migration of their target cells

Chemotaxis

movement of a cell toward a stimulus)-chemoattractants.

1. CXC group

2. CC group

3. C chemokines

4. The CX3C chemokines

Chemokines are classified into four families based on the sequence of amino acids found in their N-termini:

1. CXC group

contains a single amino acid, “X,” between the first and second cysteines. Attracts neutrophils

2. CC group

cysteines are found together, with no intervening amino acid.- attract monocytes, T cells, and eosinophils

3. C chemokines

has only a single cysteine. –attracts T and NK cells

4. The CX3C chemokines

have three amino acids between the cysteines.- attracts monocytes, NK cells and T cells

Chemokines

Recruitment to and movement of leukocytes to the areas of infection and inflammation.

monocytes and neutrophils

Chemokine receptors allow ___ and ___ to detect chemokine gradients that exist within inflamed tissues.

CXCR4 and CCR5

Chemokine receptors _____ and ____are utilized by HIV as co-receptors for infection of CD4+ T cells and macrophages

Transforming Growth Factor-β

factor that induces anti-proliferative activity in a wide variety of cell types

✓TGF-β1,

✓TGF-β2,

✓TGF-β3

3 isoforms of Transforming Growth Factor-β

o Active TGF-β

is primarily a regulator of cell growth, differentiation, apoptosis, migration, and the inflammatory response.

Transforming Growth Factor-β

• acts as both an activator and an inhibitor of proliferation.

• regulates the expression of CD8 in CD4-CD8 thymocytes and acts as an autocrine inhibitory factor for immature thymocytes.

• blocks the production of IL-12 and strongly inhibits the induction of IFNgamma (IFN-γ).

• inhibits the activation of macrophages and the growth of many different somatic cell types and functions as an anti-inflammatory factor for mature T cells

• inhibits proliferation and may function as an autocrine regulator to limit the expansion of activated cells

Interferons

First identified as soluble substances produced by virally infected cells that interfere with the ability of viruses to replicate.

Type I

Type II

Type III

Types of Interferons

Type I

the primary antiviral interferons

✓ consisting of IFN-α (product of dendritic cells and macrophages) and IFN-β (produced by a wide variety of infected cells) ,

✓ the most important cytokines in the response to viral infection

Type II

-primarily produced by T cells and NK cells

✓ associated with one particular form of adaptive immune response, known as a Th1 response

Type III

Mainly found on epithelial cells, lining the gut and lungs. (localized antiviral role)

o AKA interferon-lambdas

interferon-lambdas

Type III interferon is also known as?

TYPE I INTERFERON

halts protein translation and inducing production of RNases that target viral RNAs.

• recruits innate lymphocytes, such as natural killer (NK) cells, to sites of viral infection.

✓combination of IFN-α and IFN-β activity and NK cell killing constitutes the most important innate defense mechanism against viral infection.

• to augment the activity of NK cells, type I IFNs also enhance the expression of class I major histocompatibility complex (MHC) proteins on target cells.

• helps protect against certain malignancies

CD4-positive T helper (Th) cells

Cytokines associated with adaptive immunity are mainly secreted by T lymphocytes especially

TH1

TH2

TH17

Treg cells

T helper cells subpopulations:

TH1

they produces IFN-γ & TNF-α (activate macrophages)

TH2

they secrete IL-4, IL-5, IL-13 (differentiation of B cells into antibody-producing plasma cells and recruit other cells)

TH17

they produce IL-17 and IL-22 (recruit neutrophils)

Treg cells

they produce immunosuppressive cytokines IL-10 and TGF-β (suppress activity of other T cells and prevent excessive or self-destructive immune responses)

Cytokine IL-12

✓causes differentiation to the Th1 lineage, a change often observed in response to infections with viruses and intracellular bacteria

✓ produced by Dendritic cells

Cytokine IL-4

drives antibody-mediated immunity

Cytokine IL-3

✓production of Th17

Cytokine TGF-β

✓production of Th17

Th1 Cells

ocytokine IL-12:

✓is secreted by DCs in response to infections with viruses and intracellular bacteria

✓induces the transformation of Th1 cells from naïve T helper cells. osecrete cytokines that cause antigen-activated B cells to produce IgG1 and IgG3 antibodies ✓capable of opsonizing pathogens and fixing complement opromotes cell-mediated immunity

✓CD8-positive cytotoxic T cells that kill infected host cells and activated macrophages that are more effective at killing intracellular bacteria.

Interleukin 2 (IL-2) aka T-cell growth factor

• drives the growth and differentiation of both T and B cells and enhances the lytic activity of NK cells.

• with IFN-γ, IL-2 causes naïve helper T cells to differentiate into Th1 cells

Interferon-γ (IFN-γ)

• primary cytokine of the Th1 response

• associated with cell-mediated immunity, IFN-γ tends to increase the expression of genes that shape the responses of T cells and macrophages.

• Increases expression of class I and II MHC molecules on antigen-presenting cells (APCs).

• potent activator of macrophages ✓increases their ability to kill ingested microbes. The resulting “super” macrophages possess enhanced phagocytic and cytotoxic abilities.

Cytokine Interleukin 2 (IL-2)

Type II Interferon, Interferonγ (INF-y

Cytokines produced by Th1 Cells

Interleukin 4 (IL-4)

Interleukin 10 (IL-10)

Type II Interferon, Interferonγ (INF-y

oInterleukin-4 (IL-4) aka B cell growth factor I

is expressed on lymphocytes and on numerous nonhematopoietic cell types.

• induces the production of MHC-I, IL-4, IL-5, IL-13, and the costimulatory molecules CD80 and CD86.

• Regulates Th2 differentiation and proliferation • Promotes the production of IgG2a and IgE

TH17 cells

play an important role in host defense against bacterial and fungal infections at mucosal surfaces

Upon an encounter with bacteria or fungi, APCs secrete cytokines, which differentiate Th17 subsets of cells.

• secrete cytokines (IL-17) necessary for the continuous recruitment of neutrophils ✓ IL-17A and IL-17F induce epithelial cells, endothelial cells, and fibroblasts to produce CXC ligand 8 (CXCL-8)which is crucial for the recruitment of neutrophils to the site of inflammation.

• important for long-term maintenance of the anti-microbial response during chronic bacterial infections.

IL-10

produced by monocytes, macrophages, CD8+ T cells, and CD4+ Th2 cells.

• has anti-inflammatory and suppressive effects on Th1 cells.

IFN-γ production

one of the major effects of IL-10 is inhibition of

T-regulatory cells

third major subclass of CD4-positive T cells.

✓CD4

✓CD25

✓the transcription factor FoxP3

T-regulatory cells

T-Regulatory Cells

• establishes peripheral tolerance to a wide variety of selfantigens as well as harmless antigens, such as those found in foods and the environment.

• the production of suppressive cytokines, such as IL 10 and TGF-β

• disruption of T-cell metabolism

• direct cytotoxic killing of T cells and APCs

• modulation of signaling between APC and T cells

Colony-stimulating factor

Function: stimulate the formation of colonies of cells in the bone marrow (hematopoiesis

✓IL-3 ✓erythropoietin (EPO),

✓granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF),

✓granulocyte–macrophage colony-stimulating factor (GM-CSF

Examples of Colony stimulating factor

Interleukin 3: multi-lineage

• induces bone marrow stem cells to form T and B cells (drives the stem cells into the lymphocyte differentiation pathway) • cellular differentiation:

GM-CSF / Granulocyte-Macrophage Colony Stimulating Factor

acts to drive differentiation toward other WBC types

Erythropoietin/ EPO

regulates RBC production in the bone marrow, but it is primarily produced in the kidneys.

Multiplexed ELISAs

Microbead assays

ELISpot assays

Clinical Assays for Cytokines

Multiplexed ELISAs

• allow for simultaneous detection of several cytokines from serum or plasma in a single test run. • In the microarray format, each well on the slide contains a microarray of spotted antibodies, with “spots” for each of the cytokines plus additional “spots” for positive and negative controls. The replicate spots allow for the acquisition of reliable quantitative data from a single sample

Microbead assays

detection of multiple cytokines in a single tube

ELISpot assays

allow the detection and enumeration of individual cytokine-secreting cells.