10.3 the second line of defence

Question 1

what is the second line of defence?

Answer 1

to destroy pathogens that make it past the chemical and physical barriers of the first line of defence.
- non-specific and innate.
- involves white blood cells.

Question 2

what are platelets?

Answer 2

1. blood cell fragments that circulate in the bloodstream
2. responsible for blood clotting to prevent bleeding
3. do not interact with pathogens

Question 3

what are mast cells?

Answer 3

1. non-specific
2. found in connective tissue rather than in blood or lymph
3. produce and release histamine to trigger inflammation

Question 4

what are neutrophils?

Answer 4

1. non-specific, type of phagocyte
2. most common type of WBC
3. matures in the blood
4. primarily attacks bacteria
5. release cytokine to attract other leukocytes
6. release antimicrobial compounds to destroy membranes of bacteria and fungi

Question 5

what are macrophages?

Answer 5

1. non-specific
2. type of phagocyte
3. circulate in the blood but mature at the site of infection
4. release cytokines to attract other leukocytes
5. antigen-presenting cell. presents the pathogen’s antigen on its own surface to help activate other leukocytes

Question 6

what are natural killer cells?

Answer 6

1. non-specific
2. mature in the bone marrow and lymph nodes before entering the bloodstream,
3. attack virus-infected and cancerous cells
4. respond quickly

Question 7

what are cytokines?

Answer 7

1. protein signalling molecules, trigger a variety of immune system responses
   - cause more WBCs to be produced
   - activate WBCs
   - regulate WBC function
   - attract more WBCs to the site of infection or injury
   - induce inflammation and fever

Question 8

what are complement proteins?

Answer 8

1. increase the intensity of the inflammatory response
2. help the process of phagocytosis
3. destroy cellular pathogens directly by lysis

Question 9

what is histamine?

Answer 9

substance that trigger the inflammatory response, causes blood vessels to dilate and become leaky. the endothelial cells of the capillaries spread apart to allow WBCs and complement proteins to move out of the blood vessel and into the infected tissue. capillary dilation also increases blood flow in general, causing the area to become red, swollen and hot.

Question 10

what is the inflammatory response?

Answer 10

• to bring WBCs to the site of injury or infection
  example of inflammatory response
  1. you step on a rusty nail and cut your foot. bacteria and other pathogens enter the body.
  2. platelets release blood-clotting factors and help to close the wound to prevent more pathogens from entering the body
  3. damaged cells release cytokines, which attract neutrophils to the site of injury. mast cells near the injury release histamine. histamine causes the capillaries to dilate and become ‘leaky’. leaky capillaries allow WBCs and immune chemicals to move out of the blood vessels and into the infected tissue
  4. neutrophils are activated by cytokines and produce compounds to break down bacterial and fungal cell walls. neutrophils attract macrophages by releasing more cytokines. complement proteins break holes in the membranes and cell walls of the pathogens, causing them to lyse
  5. macrophages are activated and also release cytokines to continue attracting more WBCs. activated neutrophils and macrophages ingest pathogens and foreign particles by a process called phagocytosis
  6. the process continues until all pathogens have been destroyed and the wound is healed.

Question 11

what is a fever?

Answer 11

1. secondary immune response. body core temperature is increased above the normal homeostatic set point. thermoregulatory centres in the hypothalamus increase the set point in response to the cytokines released by WBCs
2. increased temp, leads to higher metabolic rates of healthy cells, speeds up repair of damaged tissue. vasodilation and increased blood flow bring WBCs to the site of infection
3. enzymes of pathogens denature, slows spread of infection.