Structure Of The Immune System

Question 1

What are the two arms of the immune system?

Answer 1

Innate: fast, non-specific, immediate, PAMPs and early induced response
Adaptive: slow but highly specific, antigen driven, mediated by lymphocytes and late response

Question 2

What are the barriers of the immune system?

Answer 2

Tissue and mucus

Question 3

What is haematopoeisis?

Answer 3

Differentiation and maturation of haematological cells

Two lineages; erythroid and lymphoid

Question 4

What are the innate immune cells?

Answer 4

Monocytes
Neutrophils
Macrophage 
Mast cells
Basophils
Eosinophils 
Dendritic cells
Non toxic ILCs
Natural killer cells
γδ T cells

Question 5

What are monocytes?

Answer 5

large, horse shoe shaped nucleus, recruited to tissue and differentiate into tissue specific macrophages

Question 6

What are neutrophils?

Answer 6

multi lobed nucleus and granular cytoplasm, 40-95% of total wbc, migrate into tissue and act as phagocytes, important in bacterial infections, produce anti microbial peptides

Question 7

What are mast cells?

Answer 7

Round nucleus
Precursors differentiate in tissues
Allergic response- cross linking of IgE
Release of granules

Question 8

What are basophils?

Answer 8

Largest granulocyte
Similar to mast cells (IgE)
Fewer but larger granules 
Differentiate and mature in bone marrow 
Circulate in periphery but can infiltrate tissue

Question 9

What are eosinophils?

Answer 9

Bi-lobed nucleus and protein granules
Granules can kill larger pathogens
Important in parasitic infection and allergy
Can do phagocytosis but not main role

Question 10

What are dendritic cells?

Answer 10

Most potent APC
Concentrated in secondary lymphoid organs
Professional phagocytes
Various non-self receptors

Question 11

What are non-cytotoxic ILCs?

Answer 11

Classical lymphoid morphology but no cell surface markers
Three groups;
ILC1: involved in immunity to intracellular bacteria and parasites
ILC2: involved in anti-helminth immunity, allergic inflammation and tissue repair
ILC3: can promote antibacterial immunity, chronic inflammation and tissue repair

Question 12

What are natural killer cells?

Answer 12

Develop in bone marrow
Innate sentinels
Kill virus infected cells

Question 13

What are γδ T cells?

Answer 13

Type of T cell with γ and δ sub units
Not restricted to presented peptide and recognise while protein and free Ag
Mostly in gut

Question 14

What are the cells of the innate immune system?

Answer 14

Naive
T cells
B cells

Question 15

What are naive lymphocytes?

Answer 15

Small, motile and morphologically indistinguishable
Short life span
Thin rim of cytoplasm around condensed nucleus

Question 16

What are T cells?

Answer 16

Progenitors from bone marrow migrate to thymus for maturation and expansion 
98% die due to positive and negative selections against them
Several types;
T helper: assist other leukocytes
Cytotoxic: destroy infected cells
Memory:antigen specific 
NKT: recognise glycolipid Ag on CD1d
γδ Τ cells
Regulatory

Question 17

What are B cells?

Answer 17

Progenitors arise and mature in bone marrow
Migrate to spleen and lymph nodes
Antigen blinds to B cell receptor
Types:
Plasma cell; antibody producer
Memory; dormant ready for secondary infection
Follicular; most common and generate high affinity antibody
Marginal zone; live in spleen and act as first line defence against blood pathogens
Regulatory

Question 18

What is opsonisation?

Answer 18

Particles targeted for destruction by an immune cells known as a phagocyte

Question 19

What are routes of antigen presentation?

Answer 19

MHC 1 and 2

1: peptides from cytosol to CD8 T cells
2: peptides from vesicules to CD4 T cells