2.7: The Innate Immune System

Question 1

Innate immune system

Answer 1

• Innate or “natural” immune system, aka the second line of defence
• Non-sepcific responses to pathogens
• Rapid, non-learned response
• Has a similar response to all infections: fever or inflammation

Question 2

What the innate system involves

Answer 2

• Involves phagocytes, the non-self recognition of pathogens, cells such as WBCs and killer cells, and the inflammatory response.
• Once the pathogen enters the body:
  1. The affected area becomes red, hot, and swollen (inflammed)
  2. Damaged cells release histamine, a chemical that increases blood flow to the infected area
  3. Within the blood is special white blood cells called neutrophils (dead neutrophils form pus)

Question 3

Phagocytes

Answer 3

• Type of white blood cell that has the ability to ingest, and sometimes digest, foreign particles
• Carries out process known as phagocytosis/endocytosis
• WBCs known as neutrophils and macrophage, which are types of phagocytes, engulf the pathogen and use organelles to break down the pathogen by converting it into a osluble product
• The remains of the pathogen are removed through exocytosis
• Macrophages and neutrophils are mainly found in the lymphatic system

Question 4

Natural Killer Cells (NKCs)

Answer 4

• These cells recognise protein markers as ‘non-self’ or foreign cells
• NKCS will release cytokines, small proteins that are crucial in controlling the growth and activity of other blood cells and immune system cells that help the body’s immune and inflammation responses

Question 5

What is the inflammatory response

Answer 5

• Characterised by swelling, redness, pain and heat from a physical injury and the entry of pathogens
• Physical injuries may stimulate the release of histamine, a chemical that causes arterioles to widen, allowing greater blood flow to the area. Therefore, more WBCs reach the infection site. Histamine also increases the permeability of the blood vessels, making it easier for blood to reach the site of infection.

Question 6

Process of phagocytosis

Answer 6

1. Phagocyte engulfs pathogen via endocytosis
2. Pathogen enclosed inside phagocyte
3. Lsyosome (types of organelle with enyzmes) merges with pathogen
4. Enzymes break pathogen down
5. Less harmful products of breakdown released via exocytosis

Question 7

neutrophils

Answer 7

neutrophils are one of the first immune cells to respond. They travel to the site of infection, where they destroy the microorganisms by ingesting them and releasing enzymes that kill them. Neutrophils also boost the response of other immune cells.