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Foundations in Microbiology

Chapter

17

PowerPoint to accompany

Fifth Edition

Talaro

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Disorders in Immunity

Chapter 17

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Immunopathology Allergy, hypersensitivity an exaggerated,

misdirected expression of immune responses

Involves the same types of immune reactions asthose at work in protective immunities.

Autoimmunity abnormal responses to self Ag

Immunodeficiency deficiency or loss ofimmunity

Cancer results from a lack of surveillance

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Type I Hypersensitivity

Atopy any chronic local allergy such as

hay fever or asthma

Anaphylaxis a systemic, often explosive

reaction that involves airway obstruction

and circulatory collapse

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Mechanism of Type I

sensitizing dose on first contact with allergen, specificB cells form IgE which attaches to mast cells and

basophils

provocativedose - subsequent exposure with the sameallergen binds to the IgE-mast cell complex

degranulation releases mediators with physiologicaleffects such as vasodilation and bronchoconstriction

symptoms are rash, itching, redness, increased mucous

discharge, pain, swelling, and difficulty breathing

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Role of Mast Cells & Basophils Mast cells are located in the connective tissue

of virtually all organs; high conc. in lungs, skin,

GI and genital tract

Basophils circulate in blood, migrate into

tissues

each cell can bind 10,000-40,000 IgE

cytoplasmic granules contain physiologically

active cytokines, histamine, etc

cells degranulate when stimulated by allergen

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Chemical mediators

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Systemic Anaphylaxis

Sudden respiratory and circulatory

disruption that can be fatal in a few minutes

Allergen and route are variable

Bee stings, antibiotics or serum injection

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Strategies for circumventing allergic

attacks

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Blocking Ab

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Type II Hypersensitivity

Reactions that lyse foreign cells

Involve antibodies, complement, leading to

lysis of foreign cells

Transfusion reactions

ABO blood groups

Rh factor hemolytic disease of the newborn

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Type III Hypersensitivity

A large quantity of soluble foreign Agstimulates Ab that produce small, solubleAg-Ab complexes

Immune complexes become trapped intissues & incite a damaging inflammatoryresponse

Arthus reaction local reaction to series ofinjected Ag to same body site

Serum sickness systemic disease resultingfrom repeated injections of foreign proteins

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Autoimmunity In certain type I & II hypersensitivities, the immune system

has lost tolerance to self molecules and formsautoantibodies and sensitized T cells against them.

More common in females

Disruption of function can be systemic or organic specific

Systemic lupus erythematosus

Rheumatoid arthritis

Endocrine autoimmunities

Myasthenia gravis Multiple sclerosis

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Type IV Hypersensitivity

Cell-mediated

A delayed response to Ag involving activation of

and damage by T cells Delayed allergic response skin response toallergens tuberculin skin test, contact dermititisfrom plants, metals, cosmetics

Graft rejection reaction of cytotoxic T cellsdirected against foreign cells of a grafted tissue;involves recognition of foreign HLA

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Immunodeficiency diseases Components of the immune response system are absent.

Deficiencies involve B and T cells, phagocytes, andcomplement

Primary immunodeficiency genetically basedcongenital lack of B-cell and/or T cell activity

B cell defect agammaglobulinemia patient lacksantibodies

T cell defect thymus is missing or abnormal

Severe combined immunodeficiency - both limbs oflymphocyte system are missing or defective; noadaptive immune response

Secondary (acquired) immune deficiency due to

damage after birth (infections, drugs, radiation) AIDS

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Cancer

Overgrowth of abnormal tissue arises due to

malfunction of immune surveillance

Tumors may be benign (nonspreading) ormalignant (a cancer) that spreads from tissue of

origin to other sites

Malignant tumors may be

carcinomas originate from epithelial tissue

sarcomas originate from embryonic connective tissue

Cancers occur in nearly every cell type

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Characteristics of cancerous growths

Disorganized behavior and independence

from surrounding normal tissues

Permanent loss of cell differentiation

Expression of special markers on their

surface

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Interrelationship between genes and

cancer1. Cancer cell often have damaged chromosomes

2. A specific alteration in a gene can lead to cancer

3. Predisposition for some cancers is inherited

4. Rates of cancer are highest in individuals who cannotrepair damaged DNA

5. Mutagenic agents cause cancer

6. Cells contain genes that can be transformed to cancer-causing oncogenes

7. Tumor-supressor genes exist in the normal genome

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Mechanism of Cancer

Some type of gene alteration turns a normalgene (proto-oncogene) that regulates the

onset of mitosis into an oncogene The oncogene overrides normal mitotic

controls and cause the cell to dividecontinuously

Tumor suppressor genes may be missing orinactivated

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Role of viruses in cancer

Some viruses carry oncogenes whose products

cause transformation of host cells into cancer

cells Viral genome may be inserted into regulatory

sites

Human papillomavirus cervical cancer Epstein-Barr virus Burkitts lymphoma

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Function of immune system in

cancer Cells with cancer-causing potential arise constantly

in the body but the immune system normallydiscovers and destroys them

Cell-mediated immunity, TC, NK & macrophages,

antibodies

Immune system fails in cancer may not be immunogenic enough

may retain self-markers and not be targeted

Maybe a slight or transient failure allows cancer todevelop