Immunity Chapter 40

The nature of disease

Infectious diseases Any disease caused by the presence of pathogens in the body

Pathogens Disease-causing agents Bacteria, protozoans, viruses, fungi, parasites

Sources  soil, water, food, infected animals

Determining cause of a disease Some are caused by pathogens 50% Inherited Aging

Robert Koch Identified the first pathogen in 1876 Anthrax bacterium from cattle

The spread of infectious disease Must be able to survive People Animals Water and food Soil

Direct contact Passed directly from person to person STDs

Indirect contact Passed through objects like doorknobs The common cold

Through a vector  animals or objects Malaria  mosquito Lyme disease  deer tick

Airborne Passed through the air as droplets Colds, the flu, SARS

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

Patterns of disease

Endemic Constantly present in a population The common cold

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

Pandemic People worldwide are afflicted with the same disease HIV

Treating diseases Antibiotics  substances produced by 1 microorganism to kill or inhibit the growth of another microorganism Not effective against viruses Problem  bacterial resistance

Defense against infectious diseases

Body’s earliest lines of defense Innate immunity Body’s earliest lines of defense

Skin Physical barrier

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

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

Steps of the inflammatory response

Phagocytosis of pathogens  microorganisms 3 types of phagocytes Monocytes  small, immature macrophages Macrophages  engulf and digest pathogens Phagocytosis

Phagocytosis continued Neutrophils  engulf and digest Pus  dead macrophages and body fluids

Interferons Proteins that protect against viruses Produced by infected body cells Diffuse into environment  inhibits viral multiplication

Acquired immunity Defending against a pathogen by gradually building up resistance Works with innate immunity

Acquired continued Antigens  non-self Antibodies  produced in response Can take days or weeks Antibody and cellular immunity

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

T cell mechanism of action

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

B cell mechanism of action

Passive immunity Antibodies from an outside source Natural  maternal immunity Artificial  injections from animal or other human

Active immunity Body produces antibodies and killer T cells Natural  having the disease once Secondary immune response is faster

Active continued Artificial  vaccines Attenuated  using weakened microbes for exposure Edward Jenner  1st safe vaccine for cowpox

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

Lymphatic system cont. Lymph nodes  bean-shaped glands that filter pathogens from lymph Tonsils, neck, armpits, groin Produce lymphocytes (WBCs)

Lymphatic system cont. Spleen  stores lymphocytes Filters and destroys bacteria and old RBCs Thymus  lymphocytes are matured

The lymphatic system

Immune System Disorders

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

HIV life cycle

Allergies Overreaction to an antigen Release of histamine  inflammatory response Antihistamines block action Common allergens  pollen, food, dust, animal hair

Autoimmune diseases Produce antibodies against self Rheumatoid arthritis  cartilage in joints Multiple sclerosis  motor responses

Autoimmune continued Lupus erythematosis  against DNA SCID  severe combined immunodeficiency

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