Phagocytosis

Question 1

What is job of phagocytes?

Answer 1

Fight new infection and present antigens

Question 2

What are the professional phagocytes?

Answer 2

1. Neutrophils
2. Macrophages
3. Dendritic cells

Question 3

How do phagocytes identify pathogens?

Answer 3

Recognising patterns on their surface using receptors

Question 4

Describe process of phagocytosis

Answer 4

1. Pathogens engulfed by cell membrane to form phagosome
2. Phagosome fuses with lysosome containing digestive enzymes - forming phagolysosome
3. Digestive enzymes in phagolysosome digest pathogen
4. Formation of residue body containing indigestible material
5. Indigested material secreted by fusion of residual body with cell membrane

Question 5

What happens once phagocytes have digest pathogen down to their component proteins?

Answer 5

Present digested protein antigens to cells of immune system via MHC on their surfaces

Question 6

What is purpose of MHC?

Answer 6

Safety mechanism to prevent immune system being activated too easily by ensuring T cells only react to antigen if presented with MHC II complex

Question 7

Which cells have MHC I on their surface?

Answer 7

All cells

Question 8

Which cells have MHC II on their surface?

Answer 8

Professional phagocytes and antigen-presenting B cells

Question 9

How are antigens held onto surface of cell?

Answer 9

By MHC II receptors that bind peptides

Question 10

What is job of APCs?

Answer 10

Presented to T cell, causing activation of B cells