The Immune System: Innate Host Defenses
1. Name the two major categories of innate (nonspecific) defenses:
• _____________________________
__________
• _____________________________
___________
2. Surface barriers include the ____________ and ________________ of the respiratory, gastrointestinal and genitourinary tracts.
3. List the three properties of skin that help it resist invasion:
• ___________________________
• ___________________________
• ___________________________
4. The mucus membranes not only provide a barrier, but they also produce a variety of protective chemicals. For example, the stomach secretes _____________ enzymes and has a very _____ pH. The respiratory and digestive tracts are lined with ___________ that traps pathogens.
5. Once the surface barrier has been broken, the second line of defense, the innate internal defense system (nonspecific defense system), attempts to limit the spread of pathogens. Name the 5 components of the innate internal defense system:
• ___________________________
• ___________________________
• ___________________________
• ___________________________
• ___________________________
6. Neutrophils and monocytes/macrophages (monocytes develop into macrophages in the tissue) are the two types of phagocytes discussed. Answer the following questions by circling the correct answer.
Which phagocyte is most abundant? Neutrophil or Monocyte
Which phagocytizes more pathogens? Neutrophil or Macrophage
Which cell is not found in healthy tissue? Neutrophil or Macrophage
7. A phagocyte recognizes and binds to molecules found on pathogens using special membrane receptors, such as the ______________ receptor and the ___________ (____) receptor.
8. At least 10 different TLRs have been identified on human phagocytes. Two reactions are triggered when TLRs recognize a pathogen:
• _____________________________
____________
• _____________________________
_____________________________
_____
9. A phagocyte engulfs a pathogen and brings it inside the phagocyte in a vesicle called a _____________, which later fuses with a lysosome and is then called a __________________.
10. Name three ways the pathogen is destroyed:
• _____________________________
_____________________________
_
• _____________________________
_____________________________
_
• _____________________________
_____________________________
_
11. Many pathogens have evolved strategies to avoid being killed by phagocytes. For example, some bacteria enclose themselves in capsules. _______________ is a process of coating bacteria to enhance phagocytosis by a macrophage. Phagocytes have receptors that can attach to opsonins on the bacteria. Two factors can act as opsonins:
• __________________
• __________________
12. Certain _______ (from the adaptive defense system) can enhance the killing process within a macrophage. This happens when the macrophage presents antigens from the bacteria to this cell. This is an example of the interaction between the innate and adaptive defense systems.
13. ______________ cells are a type of lymphocyte, but, unlike the B and T cells, they are not specific. However, they can still recognize abnormal cells. T cells look for the presence of abnormal antigens on the cell surface, while these cells look for the ____________ of normally occurring self-proteins.
14. NK cells kill like ___________ T cells; direct contact with a target cell causes it to undergo ____________, a form of cellular suicide.
15. Name the two types of antimicrobial proteins:
• ______________________
• ______________________
16. Interferons are cytokines that do the following three things:
• ____________________________
• ____________________________
• ____________________________
17. What causes a cell to secrete interferons? _____________________________
__
18. The interferons secreted by this cell bind to receptors on nearby cells, causing these nearby cells to produce proteins that __________________ by degrading ____________ and preventing synthesis of _________________.
19. The complement system is a cascade of interdependent proteins which enhance both the innate and adaptive defenses. When activated, these proteins can:
• _____________________________
_______________
• _____________________________
_______________
• _____________________________
_______________
20. Both adaptive and innate defense systems can activate this cascade via several pathways. For example:
• _________ on cells activate the cascade via the classical pathway.
• _________ bind to sugars on the surface of bacteria (___________ pathway).
• A lack of ___________ proteins on body cells active the alternative pathway.
21. All three pathways cause activation of the C3 protein, which splits into two fragments, C3b and C3a. What do these fragments do?
• C3a causes ______________________.
• C3b causes ______________________.
22. C3b cleaves C5 into two parts:
• C5a causes __________________.
• C5b combines with other complement proteins to form the ________________________ (____), which causes the cell to lyse.
23. Name the four cardinal signs of inflammation:
• ____________________
• ____________________
• ____________________
• ____________________
24. The purpose of inflammation is to bring __________ and ________ into an injured area. This action accomplishes three things:
• Prevents _______________________
• Disposes of _____________________
• Sets the stage for _________________
25. When tissues are injured, macrophages release chemical mediators, called inflammatory mediators. These chemical mediators cause two key effects:
• __________________, which causes redness and heat
• ______________________, which causes swelling and, thus, pain
26. These chemical mediators activate cell adhesion molecules on endothelial cells. _________________ is the process where neutrophils and monocytes bind to these cell adhesion molecules. When neutrophils bind to these molecules, they are activated and leave the blood vessel by a process called ____________. Once in the tissue, the neutrophils follow a chemical trail to the site of infection. This process is called ______________.
27. The leakiness of the capillaries allows plasma and proteins to leak into the injured area. What three important classes of proteins enter the affected area?
• _______________________
• _______________________
• _______________________
28. In addition to the complement system, other chemicals act as inflammatory mediators:
• _______________________
• _______________________
• _______________________
29. Bacterial components and cytokines act as ___________, which cause the body's thermostat to set its temperature higher, thus causing a __________. This elevated body temperature is advantageous to our defense system because:
• _____________________________
___________________________
• _____________________________
___________________________
• _____________________________
___________________________
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