Immune System Primary Function: To protect your body from pathogens. Pathogens: Bacteria, viruses, fungus, or proteins that causes illness. Spleen: stores lymphocytes and filters blood Thymus: where T cells mature Bone marrow: where blood cells are formed
Types of Immunity Innate Immunity: - present before exposure to pathogens - is nonspecific Acquired Immunity: - develops after exposure to pathogens - is very specific
Innate Immunity: External Skin - physical barrier that prevents entry of pathogens - secretions from the skin cause it to be acidic enough to prevent colonization of many pathogens
Innate Immunity: External Mucous membranes - Produce mucus, a fluid that traps pathogens - Can contain enzymes like lysozyme that digest the cell walls of many pathogens
Innate Immunity: External Cilia - In the trachea, ciliated epithelial cells sweep upward, preventing the microbes from entering the lungs Figure 43.3 10m
Innate Immunity: Internal Phagocytic cells: attach to their prey using surface receptors and engulf them (endocytosis), forming a vacuole that fuses with a lysosome. Macrophages are a type of phagocytic cell.
Innate Immunity: Internal Natural Killer cells: Attack virus-infected cells and cancer cells. Cause apoptosis (cell death) in the cells they attack.
Innate Immunity: Internal Inflammatory Response: injured cells release chemicals (histamines) that cause phagocytic cells to gather at the site. Pathogen Pin Macrophage Chemical signals Capillary Phagocytic cells Red blood cell Blood clotting elements Blood clot Phagocytosis Fluid, antimicrobial proteins, and clotting elements move from the blood to the site. Clotting begins. 2 Chemical signals released by activated macrophages and mast cells at the injury site cause nearby capillaries to widen and become more permeable. 1 Chemokines released by various kinds of cells attract more phagocytic cells from the blood to the injury site. 3 Neutrophils and macrophages phagocytose pathogens and cell debris at the site, and the tissue heals. 4
Acquired Immunity Antibodies: Proteins that recognize foreign molecules and mark them for destruction.
Acquired Immunity B cells and T cells: - Circulate in the blood - Made in bone marrow - B cells produce antibodies - T cells attack pathogens
Acquired Immunity Primary Response: B or T cells recognize the pathogen and reproduce. This creates many new cells, including memory cells.
Antibody concentration Acquired Immunity Secondary Response: Memory cells cause a faster, more efficient response to a pathogen Antibody concentration (arbitrary units) 104 103 102 101 100 7 14 21 28 35 42 49 56 Time (days) Figure 43.13 Antibodies to A to B Primary response to antigen A produces anti- bodies to A 2 Day 1: First exposure to 1 Day 28: Second exposure to antigen A; first antigen B 3 Secondary response to anti- gen A produces antibodies to A; primary response to anti- gen B produces antibodies to B 4
Allergies Allergies overly sensitive response by your immune system to a molecule (allergens) Cause: Cells in your immune system release histamines that cause an inflammatory response Figure 43.20 1 2 3 Allergen IgE Histamine Granule Mast cell
Infectious Diseases Any disease caused by “germs” that can be spread from one person to another. Germs include viruses, bacteria, and fungi.
Infectious Diseases: Whooping cough Cause: Bacterial (Bordetella pertussis) Symptoms: Severe coughing fits that can cause fractured ribs, fainting, artery tears Spread: Direct contact with mucus from the nose/throat of infected individuals Prevention: Vaccine
Infectious Diseases: HIV/AIDS Cause: Viral Symptoms: Initially, few, if any. May have flu-like symptoms. Over time, immune system is weakened because T cells are killed. Spread: Contact with bodily fluids Prevention: Avoid body fluids from infected individuals
Vaccines Improve your immune systems ability to fight off a pathogen. Include a weakened or killed form of the pathogen or part of a pathogen. Stimulates the immune system to recognize the pathogen and create memory cells.
Infectious Diseases: Strep Throat Cause: Bacterial Symptoms: Fever, sore throat with white patches Spread: Airborne (saliva or nasal secretions) Prevention: Avoid contact with infected individuals, wash hands, keep hands away from face