32-1 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease Infection The presence of a pathogen in or on the body Pathogen.

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Defenses Against Disease Infection

The presence of a pathogen in or on the body

Pathogen A disease-causing agent

Innate immunity Nonspecific defenses to

protect against pathogens

Nonspecific defenses Species resistance

Mechanical barriers

Chemical barriers

Phagocytosis

Fever

Inflammation

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Defenses Against Disease: Specific Defenses

Immunities Protect against very

specific pathogens Antigens

Foreign substances in the body

Haptens Foreign substances too

small to start an immune response by themselves

Other substances Proteins – antibodies and

complements WBCs – lymphocytes and

macrophages Lymph system

Cytokines – assist in immune response regulation

Monokines – increase B cell production and stimulate WBC production

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Defenses Against Disease (cont.)

Two major types of lymphocytes

B Cells and T Cells

Recognize antigens in the body

T Cells Cell-mediated response Bind to antigens on cells

and attack them directly Secrete lymphokines that increase T cell production and directly kill cells with antigens

T Cells Cell-mediated response Bind to antigens on cells

and attack them directly Secrete lymphokines that increase T cell production and directly kill cells with antigens

B cells Respond to antigens by becoming plasma cells Plasma cells make antibodies Memory B cells produce stronger response with next exposure to antigen

B cells Respond to antigens by becoming plasma cells Plasma cells make antibodies Memory B cells produce stronger response with next exposure to antigen

Response

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Defenses Against Disease (cont.)

T cell activation Begins when macrophage ingests and digests

pathogen with antigen on it Antigens are placed on cell membrane of

macrophage T cell recognizes and binds to antigen and the

major histocompatibility complex (MHC) on the surface of the macrophage

Now can divide to form other types of T cells

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Defenses Against Disease (cont.)

Types Cytotoxic T cells

Protect body against viruses and cancer cells Helper T cells

Increase antibody formation, memory cell formation, B cell formation, and phagocytosis

Memory T cells Remember the pathogen that activated original T cell Later exposures trigger an immune response more

effective than initial response

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Defenses Against Disease (cont.)

Natural killer (NK) cells

Type of lymphocyte

Primarily target cancer cells

Kill on contact

Do not recognize a specific antigen

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Antibodies

Also called immunoglobulins IgA

Prevents pathogens from entering body IgD

Found on B cell membranes Thought to control B cell activity

IgE Found with IgA Involved in triggering allergic reactions

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Antibodies (cont.)

IgG Recognizes bacteria, viruses, and toxins Activates complements

IgM Large and binds to antigens on food, bacteria, or

incompatible blood cells Activates compliments

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Antibodies (cont.)

Actions that occur when antibodies bind to antigens Allow phagocytes to recognize and destroy antigens

Cause antigens to clump together, causing them to be destroyed by macrophages

Cover the toxic portions of antigens, making them harmless

Activate complement Group of proteins in serum that attack pathogens by forming holes

in them

Attract macrophages to pathogens and can stimulate inflammation

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Immune Responses and Acquired Immunity

Primary immune response occurs with first exposure to antigen Slow process Memory cells are formed

Secondary immune response with next exposure to same antigen Quick and carried out by memory cells Usually prevents person from developing disease from

the antigen

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Immune Responses and Acquired Immunity (cont.)

Naturally acquired active immunity Natural exposure to antigen – having an illness Makes antibodies and memory cells Long-lasting

Artificially acquired active immunity Injected with pathogen – immunizations Makes antibodies and memory cells Long-lasting

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Immune Responses and Acquired Immunity (cont.)

Naturally acquired passive immunity Acquired from mother

Breast milk Placenta

Short-lived

Artificially acquired passive immunity Injected with antibodies (such as antivenom) Short-lived

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Major Immune System Disorders Cancer

Uncontrolled growth of abnormal cells form malignant tumors

200 known types Treatment based on stage

0 – very early; cancer cells localizedI – spread to deeper layers or some in surrounding tissuesII – spread to surrounding tissues but contained in primary siteIII – spread beyond primary site into nearby areasIV – spread to other organsRecurrent – reappeared after treatment

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Major Immune System Disorders (cont.)

Allergies Immune response to an allergen

Can be excessive IgE antibodies bind to allergens and stimulate mast cells

to release histamine and heparin Triggers allergic response

Allergy shots Small amounts of allergen stimulates production of IgG to

prevent IgE from binding to antigen IgG antibodies do not stimulate mast cells, so immune response

is not generated

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Signs/symptoms Inhaled allergens – runny nose, sneezing, coughing, wheezing Ingested allergens – nausea, vomiting, diarrhea Skin allergens – rashes Allergens in blood – most life-threatening; can affect many

organs

Treatment Antihistamines, decongestants – OTC or prescription Epinephrine for anaphylaxis – vasoconstriction, increasing BP

Anaphylaxis – life-threatening response

Major Immune System Disorders (cont.)

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Common Immune System Disorders Autoimmune disease

Body attacks its own antigens Examples

Scleroderma Rheumatoid arthritis Multiple sclerosis Glomerulonephritis Chron’s disease Diabetes mellitus, type I

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Common Immune System Disorders (cont.)

Disorder Description AIDS Development of severe signs and symptoms

caused by HIV as it destroys lymphocytes; leaves immune system weakened and susceptible to other diseases

Chronic fatigue syndrome (CFS)

Condition of severe tiredness not relieved by rest and not related to other illnesses

Lymphedema Blockage of lymphatic vessels results in tissue swelling that increases over time

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Common IS Disorders (cont.)

Disorder Description Mononucleosis “Mono”; highly contagious viral infection

spread through saliva of infected person

Systemic lupus erythematous (SLE)

Autoimmune disorder; antibodies produces that target own cells and tissues; affects women more often than men

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In Summary Immune system is the body’s major line of defense

Primary function – protect against infection, toxins, and cancer

Specific or nonspecific defenses Lymphocytes are major cells of immune system

Immune response may be primary or secondary Medical assistant must understand immune system

Aseptic technique Infection control Educate patients