Immunity

Chapter 40

1

The nature of disease

2

Infectious diseases

• Any disease caused by the presence of pathogens in the body

3

Pathogens

• Disease-causing agents

• Bacteria, protozoans, viruses, fungi, parasites

4

• Sources soil, water, food, infected animals

5

Determining cause of a disease

• Some are caused by pathogens 50%

• Inherited

• Aging

6

Robert Koch

• Identified the first pathogen in 1876

• Anthrax bacterium from cattle

7

The spread of infectious disease

• Must be able to survive

• People

• Animals

• Water and food

• Soil

8

Direct contact

• Passed directly from person to person

• STDs

9

Indirect contact

• Passed through objects like doorknobs

• The common cold

10

Through a vector animals or objects

Malaria mosquito Lyme disease deer tick

11

Airborne

• Passed through the air as droplets

• Colds, the flu, SARS

12

Symptoms of disease

• Caused by a disruption of homeostasis

• Pathogen multiplies, damaging tissues

• Viruses take over cells

• Bacteria production of toxins– Fever, destruction of blood cells or vessels,

inhibit protein synthesis, disrupt the nervous system

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Patterns of disease

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Endemic

• Constantly present in a population

• The common cold

15

Epidemic

• Many people in an area afflicted with the same disease at the same time

• Influenza

16

Pandemic

• People worldwide are afflicted with the same disease

• HIV

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Treating diseases

• Antibiotics substances produced by 1 microorganism to kill or inhibit the growth of another microorganism

• Not effective against viruses

• Problem bacterial resistance

18

Defense against infectious diseases

19

Innate immunity

Body’s earliest lines of defense

20

Skin

• Physical barrier

21

Body secretions

• Mucous traps invaders

• Sweat, tears, saliva all contain enzymes to break down cell walls of some bacteria

• HCl in stomach also breaks down cell walls

22

Inflammation of body tissues

• Redness more RBCs– Release of histamine by WBCs and injured

cells

• Swelling, pain, heat fluid leaks from vessels into injured tissue

23

Steps of the inflammatory response

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Phagocytosis of pathogens microorganisms

• 3 types of phagocytes

• Monocytes small, immature macrophages

• Macrophages engulf and digest pathogens– Phagocytosis

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Phagocytosis continued

• Neutrophils engulf and digest

• Pus dead macrophages and body fluids

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Interferons

• Proteins that protect against viruses

• Produced by infected body cells

• Diffuse into environment inhibits viral multiplication

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Acquired immunity

• Defending against a pathogen by gradually building up resistance

• Works with innate immunity

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Acquired continued

• Antigens non-self

• Antibodies produced in response

• Can take days or weeks

• Antibody and cellular immunity

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Cellular immunity

• T cells produced in bone marrow and matured in thymus gland

• Cytotoxic (killer) T cells produce enzymes which lyse bacteria

• Helper T cells activate killers

• Suppressor T cells stop attack

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T cell mechanism of action

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Antibody immunity

• B cells produced and matured in bone marrow

• Activated by helper T cells• B cell divides into:

– Plasma cell antibodies– Memory B cell

• Complement system enzymes to help fight bacteria

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B cell mechanism of action

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Passive immunity

• Antibodies from an outside source

• Natural maternal immunity

• Artificial injections from animal or other human

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Active immunity

• Body produces antibodies and killer T cells

• Natural having the disease once– Secondary immune response is faster

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Active continued

• Artificial vaccines– Attenuated using weakened microbes for

exposure– Edward Jenner 1st safe vaccine for cowpox

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Lymphatic system

• Defense and homeostasis

• Lymph collected tissue fluid

• Lymph capillaries and veins parallel to circulatory vessels– Lymph flows toward the heart– Returns to bloodstream through ducts in the

shoulder area

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Lymphatic system cont.

• Lymph nodes bean-shaped glands that filter pathogens from lymph– Tonsils, neck, armpits, groin– Produce lymphocytes (WBCs)

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Lymphatic system cont.

• Spleen stores lymphocytes– Filters and destroys bacteria and old RBCs

• Thymus lymphocytes are matured

40

The lymphatic system

41

Immune System Disorders

42

HIV human immunodeficiency virus

• Attaches to receptor on helper T cells– Other cells cannot be activated

• RNA turned to viral DNA

• Incubation period 4-10 years

• Death caused by inability to combat other pathogens

43

HIV life cycle

44

Allergies

• Overreaction to an antigen

• Release of histamine inflammatory response

• Antihistamines block action

• Common allergens pollen, food, dust, animal hair

45

Autoimmune diseases

• Produce antibodies against self

• Rheumatoid arthritis cartilage in joints

• Multiple sclerosis motor responses

46

Autoimmune continued

• Lupus erythematosis against DNA

• SCID severe combined immunodeficiency

47

Cancer uncontrolled cell replication

• Caused by mutations in DNA viruses, chemicals, radiation, genetic predisposition

• Sarcoma connective tissue, bone, muscle

• Carcinoma epithelial tissue (skin, organs)

• 3 deadliest forms lung, colo-rectal, breast

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