o Robert Koch- “father of disease” o research focused on anthrax o Koch’s Postulates

 Initial reaction of body to ALL pathogens  Pathogen-any agent that causes disease ▪ Ex: bacteria, virus, fungi, parasites  Come into contact with the body by:  Air  Food  Water  Person-to-person contact  Animal bites

 Skin – prevents entry  Oil – traps and kills invaders  Sweat-have toxins that can kill bacteria  Mucous Membranes – epithelial tissue that protect the interior surfaces of the body. ▪ Mucous-sticky fluid that traps pathogens  Hair/Cilia ▪ Respiratory tract into digestive tract  Tears  Saliva  Ear wax

If a pathogen penetrates the first line of defense... Inflammatory Response: series of reactions that suppress infection and speed up recovery. 1. Cells are damaged. Ex: cut, pathogen invasion 2. Damaged cells release histamine o Causes increased blood flow and permeability of blood vessels around injured area o Histamine causes redness, swelling, warmth, pain o Sends signal to white blood cells to come 3. White blood cells (Phagocytes) arrive o Phagocytes ingest and destroy pathogens o 2 Types of Phagocytes: Neutrophils & Macrophages 4. Platelets arrive-seal off surrounding tissues and stop pathogens from entering the rest of the body

 Natural Killer Cells-large white blood cells that attack pathogen- infected cells  Can kill cancer cells and virus-infected cells  Pierces cell membrane to kill the cell  Fever  Increase in body temperature  Slows growth of bacteria and viruses  Promotes WBC activity  Complement System  Proteins circulate in blood and become active when they encounter certain pathogens  Some puncture infected cell membranes to kill the cell  Interferon  Protein released by virus-infected cells  Causes nearby cells to make proteins that help them resist the virus infection

When pathogens get past the NonSpecific Defense… Aimed at SPECIFIC pathogens o Immune System-cells and tissues that recognize and attack foreign substances o Tissues: o Bone marrow-makes lymphocytes o Thymus-gland where T cells mature o Lymph nodes-contain lymphocytes, filter lymph o Spleen-stores healthy blood cells, breaks down old blood cells, helps develop lymphocytes and other WBC, collects pathogens o Tonsils & Adenoids- masses of lymph tissue found in nose and throat that contain lymphocytes which produce antibodies o Cells: o Lymphocytes (WBC of the immune system) o 2 Types: o B Cells-made in bone marrow and mature there o T Cells-made in bone marrow, but mature in thymus

 Lymphocytes react to presence of antigens  Antigens-proteins on the surface of pathogens  Lymphocytes have unique receptors on surface that match specific antigens  Matching lymphocytes bind to antigen to start attack  Immune Response-reaction of the body against pathogens

 An immune response begins with:  1) Macrophage engulfs a pathogen  2) Macrophage displays fragments of the pathogen’s antigens on its surface  3) Helper T cell (lymphocyte) with matching receptors to the antigens binds to the macrophage  4) Macrophage releases proteins that activate more helper T cells

 The immune response occurs in 2 parts, which happen simultaneously  Part 1- Cell-Mediated Immune Response  Increase in Helper T cells and their division rates  Cytotoxic T cells are produced ▪ Recognize and destroy pathogen-infected cells ▪ Cytotoxic T cells have receptors that match antigens ▪ Puncture the cell membrane to kill it

 Part 2- Humoral Immune Response  B cells that have matching receptors to the antigen divide  Change into plasma cells and memory cells ▪ Plasma cells-make antibodies  Antibodies-defensive proteins that are released into blood ▪ Antibodies bind to specific antigen ▪ They do not destroy the pathogens directly

o Some B cells turn into memory cells o Lymphocytes that will not respond the 1 st time they meet an antigen, but will recognize and attack with later infections o Explains why you get most diseases only once o Primary Immune Response o First time the body encounters an antigen o Memory cells produced for that specific antigen o Secondary Immune Response o Later infection by the same pathogen o Memory cells respond faster and stronger o Exception: Cold and Flu viruses

 Immunity-the ability to resist an infectious disease  Memory cells  Vaccinations  Vaccine-solution that contains a dead or weakened pathogen  Body produces primary immune response ▪ Memory cells  Booster shots

 Can react to harmless antigens in ways that can be harmful  Allergies, Asthma, Autoimmune Diseases  Allergy-a physical response to an antigen  Many symptoms due to histamine ▪ Antihistamines-drugs that counteract effects of histamines and relieve symptoms of allergies

 Allergies can trigger Asthma  Respiratory disorder ▪ Bronchioles narrow ▪ Swelling and inflammation ▪ Difficulty breathing  Autoimmune Diseases  Disease where the immune system attacks the organism’s own cells  Ex: Multiple sclerosis ▪ Nervous system ▪ T cells attack insulating material in nerve cells in the brain, spinal cord, and nerves in eye ▪ Cause weakness, tingling, blurred vision  Severe cases can cause paralysis, blindness, death

 AIDS- Acquired Immunodeficiency Syndrome  The immune system loses its ability to fight off pathogens and cancers  AIDS results from infection by HIV  HIV-Human Immunodeficiency Virus ▪ Destroys Helper T cells  cripples the immune system  leads to AIDS  Opportunistic Infections-illnesses caused by pathogens that produce disease in people with weakened immune systems  Usually these pathogens don’t create problems in healthy people  HIV does NOT cause death, but AIDS is fatal  Death caused by weakened immune system’s inability to fight opportunistic infections and cancers  HIV is transmitted by body fluids and contaminated needles *PLAY DISCOVERYEDUCATION VIDEO*

Type of CellFunction Macrophage Engulfs and kills pathogens Helps initiate immune response NeutrophilEngulfs and kills pathogens Natural Killer CellPunctures infected cells Helper T Cell Activates cytotoxic T cells Helps B cells multiply to form antibodies Cytotoxic T CellPuncture labeled infected cells B CellLabels invaders for destruction by macrophage Plasma CellReleases antibodies Memory CellStores information about a pathogen