Defense against infectious disease

1. Defense against infectious disease Part 1 – Chapter 6.3

2. 6.3.1 Define pathogen • Any living organism or virus that causes a disease • includes: viruses, bacteria, protozoa, fungi, and worms • exposure doesn’t always result in disease due to our immune system

3. List six methods by which pathogens are transmitted and gain entry into the body.

4. Summarize the body’s three lines of defense against disease. Nonspecific Defense First line • Skin/mucous membranes • Skin secretions Second Line • WBC • Antimicrobial proteins • Inflammation Specific Defense (Immune system) Third Line • Lymphocytes • Antibodies

5. 6.3.2 Explain why antibiotics are effective against bacteria but not against viruses. • Antibiotics are chemicals that differentiate between prokaryotic and eukaryotic cells. • they damage or kill prokaryotic cells but not damage eukaryotic cells • There are different types of antibiotics: • some block bacterial protein synthesis • some inhibit new cell wall production • Viruses use our own (eukaryotic) cells to create new viruses so antibiotics aren’t effective against viruses

6. 6.3.3 Outline the role of skin and mucous membranes in defense against pathogens. • Skin: barrier to infection • Dermis: lower layer (live cells) • Epidermis: upper layer (dead cells) • Good barrier against most pathogens because cells aren’t alive • Stomach acid: kills most ingested pathogens • Mucus: lines passageways • stickiness traps pathogens preventing them from reaching cells they could infect • secretes lyzozyme which kills pathogens

7. White Blood Cells - Leucocytes 3 Classes of leucocytes • Granulocytes, which include: • Neutrophils – attracted to damage & ingulf invaders • Eosinophils & Basophils – cause inflammation in lungs and skin • Lymphocytes, which include: • B cells – make antibodies • T cells – kill infected cells • Monocytes – become macrophages that clean up debris

8. 6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and body tissues. • Phagocytosis: swallowing up of invaders by special white cells • Neutrophils: over half of WBC’s • Attracted by damage (chemicals released) • Destroy invaders at the damage site • Short life span—die in the process

9. 6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and body tissues. • Monocytes: only few of WBC’s • More effective phagocytic defense • Recognizes self vs. non-self cells • Short (hours) circulation before becoming macrophages • Macrophages engulf microbes killing with enzymes • Eosinophils: Even fewer of WBC’s • Fight off the large stuff (flukes)

10. 6.3.5 Distinguish between antigens and antibodies. • Response is the third line of defense = specific • Antigen: Antibody generator • foreign molecule recognized and causes a response by the body • causes “B Cell” to secrete antibodies • Antibody: • protein that recognizes a specific invader • B cells and T cells specialize in different types of antigens

11. 6.3.6 Explain antibody production. • Antibodies are produced by the plasma cells derived from the B cell that identified the antigen • They match and can bind to a portion of the invader (and somewhat match the antigen receptor)

13. 6.3.6 Explain antibody production. • Specific antigen type is identified • Specific B lymphocyte binds to antigen • B lymphocytes clone themselves to rapidly increase their numbers • B lymphocytes begin antibody production • Antibodies circulate bloodstream to find antigen match • Antibodies help eliminate the pathogen • Some cloned B lymphocytes remain in bloodstream & give immunity from a 2nd infection by same pathogen = memory cells

14. Distinguish between primary and secondary immune response. • Primary: first time exposure • Activation of lymphocytes after antigen is presented (creating memory cells) • 10-17 days from exposure to antigen to have maximum response • Symptoms of illness diminish & disappear as antibodies and T cells clear antigen from body • Secondary: second time exposure • The memory cells quickly and powerfully recognize the antigen and mount a stronger response (2-7 days)

15. 6.3.7 Outline the effects of HIV on the immune system. HIV (human immunodeficiency virus) EFFECTS: • AIDS (acquired immunodeficiency syndrome) • Retrovirus that destroys helper T cells • Recall that helper T cells stimulate immune response • The population of helper T’s eventually declines to the point where immunity collapses and secondary infections develop (e.g. pneumonia)

16. 6.3.7 Outline the effects of HIV on the immune system. EFFECTS: • Individuals w/AIDS are highly susceptible to opportunistic diseases, infections and cancers that take advantage of a deficient immune system • Not eliminated from the body by antibodies because: • The latent virus is invisible to the immune system • The virus changes rapidly during replication

17. 6.3.8 Discuss the cause, transmission, and social implications of AIDS. CAUSE: • Retrovirus operates by reverse-transcribing its RNA to make DNA to make RNA to make its viral proteins. • Infects Helper T-cells TRANSMISSION: • Transfer of infected cells through blood or other body secretions (mother-child, needles, unprotected sex)

18. 6.3.8 Discuss the cause, transmission, and social implications of AIDS. SOCIAL IMPLICATIONS: • Treatment is very expensive, so developing countries are very hard hit. • At present: no effective treatment for AIDS. • AZT can slow its progress by blocking reverse transcription, but its effect is temporary and it often produces serious side effects. • Education is the key to prevention.