IRCelular11 (stu)

8/3/2019 IRCelular11 (stu)

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Objectives

After working through this module, you should

be able to:

Explain the mechanisms involved in cellular

immunity.

Explain the interaction between the

components of the immune system in regulating

immune response.

Describe the mechanism of immune response

towards superantigen


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Cellular Immune Response

While humoral immune response is for

extracellular bacterial, cellular immune

response is more for intracellular bacteria,

viruses, tumours and transplants.

Cells involved in specific cellular immune

response are the T lymphocytes


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Lymphocyte ActivationMacrophage

NK cell

TH2TH1

IFN-

IL-12IFN-

Il-12, TNF-

IFN-

Il-4, IL-10

Cross-regulation

Promotes cellular immunity Promotes humoral immunity

IL-4

IL-5IL-6

IL-10

IL-13

IL-2

IFN-TNF-


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Antigen Elimination

The elimination ofantigens in the effector phase ofspecific immune responses occurs by the cooperativeactions of differentiated lymphocytes and defence

mechanisms of innate immunity

In cell-mediated immunity, activated T lymphocytessecrete cytokines, which enhance the functions of

phagocytes and other inflammatory leukocytes

However, cytotoxic T cells do not require other

cooperating mechanisms to eradicate microbes


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Antigen Elimination

Cellular Immunity

Microbe (bacteria)surviving in phagocyte

MHC-II

CD4 recognizesexogenous antigen

Activation of microbicidalfunctions of phagocyte

MHC-I

CD8 recognizes

endogenous antigen Lysis of infected cell

Microbe (virus) infecting

non-phagocytic cell


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Regulation of Immune Response

The immune response has to be regulated and

brought back to the normal status as excessiveresponse will be detrimental to the body.


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Immunoregulation

Y Y Y

Y Y Y

Antigen

Macrophage IL-1

Suppresor T cell

IL-2

IL-1

Helper T cellStimulation

B cell

Feedback

inhibition

Idiotype network

interactions


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Based on the diagram above, themechanisms of immunoregulation.

1.Control by antigen

level of exogenous antigen intensityof response

2.Feedback control by antibodyIgG inhibit responses via Fc receptor on

B-cells


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3. T-cell regulation

a. activated T-cells express Fas and FasL

which restrain unlimited clonal expansion

Fas-mediated apoptosis of activatedmature cells

b. mutual inhibition between TH1 and TH2cells suppression


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4. Idiotype networks

antigen-specific receptors on lymphocytes

can interact with the idiotypes on thereceptors of other lymphocytes to form anetwork (Jerne)

5. Genetic factors

10 genes control overall antibody response

affecting

- macrophage ag processing

- microbicidal activity

- rate of proliferation of differentiating

B-cells


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6. Immunoneuroendocrine networks

- interaction among immunologic, neurologic

and endocrinologic systems

- regulatory interdependent circuits feedback by cytokines augmentingproduction of corticosteroids shutsdown TH1 and macrophage activity

- estrogens largely responsible for the moreactive responses in females relative to

males


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7. Effects of diet and other factors on

immunity

- protein-calorie malnutrition impairs

- exercise

- trauma

- age: IL-2, TNF, IL-1, IL-6

- environmental pollution


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SUPERANTIGEN

ACTIVITY 1

Based on the diagrams below, how is

superantigen different from normal antigenin antigen recognition and stimulating animmune response?


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macrophage

lymphocytelymphocyte

macrophage

antigen

TCR TCR

Antigen piece

MHC II MHC II

ANTIGEN SUPERANTIGEN

V V V V


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References

Stites DP, Terr Al and Parslow TG. Medical Immunology. 10th Edition,Appleton & Lange, Prentice-hall International Inc. 2001.

Roitt I, Brostoff J and Male D. Immunology. 6th Edition, GowerMedical Publishing, London. 2001

Geo.F.Brooks, Janet S.Butel and Stephen A.Morse. Jawetz, Melnick,

& Adelbergs Medical Microbiology. 23rd Edition, McGraw-Hill. 2004.

Cedric Mims, Hazel M. Dockrell, Richard V.Goering, Ivan Roitt, DerekWakelin and Mark Zuckerman. Medical Microbiology. 3rd Edition,Elsevier Mosby. 2004.

Marjorie Kelly Cowan and Kathleen Park Talaro. Microbiology ASystems Approach. McGraw-Hill. 2006.

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