1. AP Biology Immune System phagocytic leukocyte Fighting the Enemy Within! Big Questions: 1.What is the purpose of a immune system? 2.How does the immune system function? 3.Why do animals have a more developed immune system?

2. AP Biology Immune Systems  Highly developed in mammals  Two types of immunity: 1. Innate immunity (nonspecific) 2. Adaptive immunity (specific) What about other organisms? Lymphatic System: Production & transport of leukocytes (WBC) Traps foreign invaders

3. AP Biology Lines of defense  1st line: Non-specific barriers  broad, external defense  “walls & moats”  skin & mucous membranes  2nd line: Non-specific patrols  broad, internal defense  “patrolling soldiers”  leukocytes = phagocytic WBC  3rd line: True immune system  specific, adaptive immunity  “elite trained units”  lymphocytes & antibodies  B cells & T cells Bacteria & insects inherit resistance. Vertebrates acquire immunity.

4. AP Biology 1st line: Non-specific External defense  Barrier  skin  Traps  mucous membranes, cilia, hair, earwax  Elimination  coughing, sneezing, urination, diarrhea  Unfavorable pH  stomach acid, sweat, saliva, urine  Lysozyme enzyme  digests bacterial cell walls  tears, sweat Lining of trachea: ciliated cells & mucus secreting cells

5. AP Biology 2nd line: Non-specific patrolling cells  attack pathogens, but don’t “remember” for next time  leukocytes  phagocytic white blood cells  macrophages, neutrophils, natural killer cells, dendritic cells  inflammatory response  increase in body temp.  increase capillary permeability  attract macrophages/neutrophils yeast macrophage bacteria

6. AP Biology 2nd line: Non-specific patrolling cells  attack pathogens, but don’t “remember” for next time  Antimicrobial proteins  Complement system – complementing protein cascade that ‘attacks’ infected cells  Interferons – infected cells release signals that stimulate surrounding cells to build up defenses yeast macrophage bacteria

7. AP Biology Inflammatory response Histamine and cytokines increase blood flow to damaged site, making it look red and puffy = INFLAMMED!

8. AP Biology Fever  When a local response is not enough  system-wide response to infection  activated macrophages release interleukin-1  triggers hypothalamus in brain to readjust bodily thermostat to raise body temperature  higher temperature helps defense  inhibits bacterial growth  stimulates phagocytosis  speeds up repair of tissues  causes liver & spleen to store iron, reducing blood iron levels  bacteria need large amounts of iron to grow

9. AP Biology Fever  Too much of a good thing?  High fevers and high body temperatures can denature the body’s own proteins….brain damage  Septic shock – overwhelming inflammatory response that involves high fever and low blood pressure  Common cause of death in critical care units

10. AP Biology  Specific defense with memory  lymphocytes  B cells - humoral response  T cells – cell mediated response  They respond to…  Antigens! 3rd line: Adaptive (active) Immunity B cell

11. AP Biology B cells  Involved in HUMORAL RESPONSE  Attacks foreign antigens in blood or lymph  Produce specific antibodies against specific antigens  Types of B cells  plasma cells  immediate production of antibodies  rapid response, short term release  memory cells  continued circulation in body  long term immunity

12. AP Biology “self”“foreign” How are invaders recognized?  Antigens - cellular ‘name tag’ proteins  “self” antigens  get no response from WBCs  Major Histocompatibility Complex – MHC Protein used by all cells for self-recognition  “foreign” antigens  Get response from WBCs  pathogens: viruses, bacteria, protozoa, parasitic worms, fungi, toxins  non-pathogens: cancer cells, transplanted tissue, pollen Mature lymphocytes are tested to make sure they can distinguish self vs. non-self

13. AP Biology What do antibodies do to invaders?

14. AP Biology

15. Humoral Immune Response

16. AP Biology T cells  Involved in CELL MEDIATED RESPONSE  Attack, learn & remember pathogens hiding in infected cells  recognize antigen fragments  also defend against “non-self” body cells  cancer & transplant cells  Types of T cells  helper T cells  alerts rest of immune system  killer (cytotoxic) T cells  attack infected body cells  memory T cells  long term immunity T cell attacking cancer cell

17. AP Biology How do T cells know a cell is infected?  Infected cells digest some pathogens  MHC proteins carry pieces to cell surface  foreign antigens now on cell membrane  called Antigen Presenting Cell (APC)  Many different WBC’s can also serve as APC  tested by Helper T cells MHC proteins displaying foreign antigens infected cell T cell with antigen receptors T H cell WANTED

18. AP Biology Cell-Mediated Response  Cytotoxic T cells destroy infected body cells or cancer cells  secretes perforin protein causing apoptosis or lysis of infected cell  Creates memory killer-T’s for further exposures

19. AP Biology What is Immunity? 2 Types: ACTIVE and PASSIVE

20. AP Biology Active Immunity  Get exposed to pathogen!  Naturally – get sick  Artificially – get a vaccination  Both methods cause memory cells to be made for future exposures. Rapid response to second exposure. You don’t even know you were exposed!

21. AP Biology

22.  Naturally  Obtaining antibodies from mother  antibodies pass from mother to baby across placenta or in mother’s milk  critical role of breastfeeding in infant health  Artificially  injection of antibodies  ex: anti-venom serum  short-term immunity Passive immunity (antibodies not immune cells)

23. AP Biology  Human Immunodeficiency Virus  virus infects helper T cells  AIDS: Acquired ImmunoDeficiency Syndrome  infections and death by opportunistic diseases  pneumonia, cancers HIV & AIDS HIV infected T cell

24. AP Biology Immune system malfunctions  Auto-immune diseases  Immune system attacks own molecules & cells  Rheumatoid arthritis  Diabetes  Multiple sclerosis  Allergies  Makes wrong antibody for foreign antigen  Allergens = proteins on pollen, dust mites, in animal saliva  At 1 st exposure you are not allergic. Allergy is confirmed after subsequent exposures

25. AP Biology