4.1.5 Phagocytes

Question 1

Phagocytes overview

Answer 1

• Produced in bone marrow
• Remove dead cells and invasive microbes
• Non-specific immune responses

3 Types :
- Neutrophils
- Macrophages
- Dendritic cells

Question 2

What are neutrophils and how do they work?

Answer 2

• Lobed nuclei
• Short lived
• Move into body tissues from blood
• Chemotaxis (Chemicals released by pathogens + histamines attract neutrophils to site of infection)
• Antibodies on pathogen trigger attack
• Cell surface membrane extends and engulfs pathogen within a PHAGOCYTIC VACUOLE (endocytosis)
• Lysosomes fuse with phagocytic vacuole secreting digestive enzymes destroying pathogen
• Neutrophil dies

Question 3

What are macrophages and what do they do?

Answer 3

• Larger than neutrophils, long lived
• Move into organs (lungs, liver, spleen, kidney, lymph nodes)
• Can carry out phagocytosis
• Mainly though, they cut up pathogen and PRESENT ANTIGENS on their surface
• Displayed antibodies recognised by lymphocytes

Question 4

What are dendritic cells and what do they do?

Answer 4

• Large
• Lengthy extensions
• Large SA
• Ingest pathogens and transport them to lymph nodes

Question 5

What happens after an antigen presenting cell is recognised?

Answer 5

• T lymphocytes produce an immune response
• T cells only bind to antigens present on antigen presenting cells
• Macrophages are the antigen presenting cell
• T cell becomes activated and divides to produce clones