Cells Involved in Immune Response

Question 1

Neutrophils - function

Answer 1

• First life of defence against all infections
• Primary phagocytic cell of innate immunity
• Phagocytose invading organisms
• Present antigens to immune system
• Release cytokines

Question 2

What are the granulocytes? What are they characterised by?

Answer 2

Neutrophils, eosinophils, basophils

Multilobed (2-5) nuclei, granules in cytoplasms

Question 3

Eosinophils - function

Answer 3

• Specifically act against multicellular parasites
• Involved in IgE mediated allergic disorders
• Release cytokines

Question 4

Basophils - function

Answer 4

Important role in allergic reactions through binding with IgE antibodies to release histamine

Question 5

Monocytes - function

Answer 5

Produced in bone marrow and travel in blood to target tissues to become macrophages

• Phagocytosis
• Antigen presentation
• Cytokine production

Question 6

Monocytes - structure

Answer 6

Largest type of leukocyte (WBC)

• Bean shaped nuclei
• Precursor of tissue macrophages

Question 7

What are macrophages derived from?

Answer 7

Derived from blood monocytes which differentiate once they reach target tissues

Question 8

Why are macrophages not found on a full blood count?

Answer 8

Tissue cells

Question 9

Macrophages - function

Answer 9

• ‘Tidy up’ pathogens, foreign debris and old/dead cells by phagocytosis
• Antigen presentation
• Can activate memory cells
• Participate in innate and adaptive immunity

Question 10

How are macrophages controlled?

Answer 10

1. Only phagocytose dying cells

2. Only phagocytose opsonised cells and pathogens

Question 11

How do macrophages only phagocytose dying cells?

Answer 11

Membrane plasma lipid profile changes when a cell dies - macrophages recognise this

Question 12

How do macrophages only recognise opsonised cells and pathogens?

Answer 12

Surface is coated with with complement proteins/antibodies so can be taken up by Fc receptor on macrophages

Question 13

Dendritic cells - function

Answer 13

Formed in bone marrow and circulate in blood until they reach target tissues

• Phagocytose pathogens before migrating to lymph nodes where they present antigens on cell surface to activate adaptive immunity
• Main ‘professional’ antigen presenting cells
• Activate T helper and memory cells

Question 14

What happens when dendritic cells reach target tissues?

Answer 14

Activated by pathogens and differentiate into mature forms

Question 15

Dendritic cells have specialised receptors on surface. What does this enable?

Answer 15

Allows it to recognise patterns of foreign molecules (e.g. clusters of sugars)

Question 16

What happens when dendritic cells present antigen to naive T cell?

Answer 16

1. T cell can proliferate
2. Daughter T cells stimulate B cells to mature and produce antibodies
3. Antibodies coat pathogens that macrophages can phagocytose them (opsonisation)

Question 17

Can macrophages present to naive T cells?

Answer 17

No but they can present to primed daughter T cells activated by dendritic cell

Question 18

What are the lymphocytes?

Answer 18

B cells, T cells, NK cells

Question 19

B cells - function

Answer 19

• Produce antibodies after maturation
• Present antigens
• Produce memory cells
• Essential for humoral immunity (antibody-mediated response)

Question 20

T cells - function

Answer 20

• Essential for cell mediated immunity
• Influences other cells
• Can kill virally infected and tumour cells
• Generate long lived memory cells

Question 21

NK cells - structure

Answer 21

Large and granular lymphocytes

Question 22

NK cells - function

Answer 22

• Innate and adaptive immunity
• Destroy pathogens and infected cells without need for prior activation
• Viral immunity and tumour rejection
• Trigger apoptosis in target cells (can kill infected cells that don’t express foreign surface antigen)