Comparative Immunology

Question 1

What does recognition by TLRs and carbohydrate-binding lectins do?

Answer 1

Activates opsonic/lytic pathways in vertebrates, coagulation cascade in arthropods, phagocytosis and pathogen lysis by antimicrobial peptides.

Question 2

TNFR in Mammals

Answer 2

Tumor Necrosis Factor Receptor.

Question 3

PGRP-LC in drosophila

Answer 3

PeptidoGlycan Recognition Protein- LC.

Question 4

Where are TLRs present?

Answer 4

In haemolymph or cell surface of immune tissues.

Question 5

What does recognition of infection activate?

Answer 5

Toll and Imd pathways in fat bodies and haemocytes, these use NF-kB and Jnk-related proteins to induce production of antimicrobial peptides.

Question 6

What are haemocytes used for?

Answer 6

Antiparasitic infection through encapsulation and melanisation.

Question 7

What do JAK-STAT release?

Answer 7

Vir-1 and Tep-1 (boosts Toll response).

Question 8

What does NF-kB release?

Answer 8

Tot-A (stress signal).

Question 9

CNS immune response

Answer 9

Produces AMPs and/or cytokines, inflammation and neuronal death and degeneration.

Question 10

Respiratory system response

Answer 10

Trachea in flies, lungs in man which produce AMPs.

Question 11

Systemic response

Answer 11

Fat body in flies and liver in man, produces AMPs and acute phase response.

Question 12

Digestive system response

Answer 12

Produce AMPs and local ROS production via Duox and Nox.

Question 13

Excretory system response

Answer 13

Malphigian tubules/kidneys produce AMPs and regulate hormones.

Question 14

Cellular response

Answer 14

Haemolymph/blood + lymph perform phagocytosis, clotting and coagulation along with cytokine secretion.

Question 15

Immune cells of drosophila

Answer 15

Plasmatocyte (phagocytosis), lamellocyte (encapsulation) and crystal cell (melanisation and clotting).

Question 16

Phagocytosis mechanism

Answer 16

Bacterium is attached to pseudopodia and is ingested which forms a phagosome, this then fuses with a lysosome with these enzymes digesting the bacteria and the products are then released.

Question 17

Functions of complement system

Answer 17

Lysis, opsonisation, activation of inflammatory response and immune complex clearance.

Question 18

Three pathways of complement activation

Answer 18

Classical, lectin and alternative.

Question 19

Classical complement activation

Answer 19

Ag:Ab complex with C1q,r,s, C4 and C2.

Question 20

Lectin pathway

Answer 20

Mannose-binding lectin binds to pathogen surface, MBL, MASP-2, C4 and C2.

Question 21

Alternative pathway

Answer 21

Does not require antibodies, C3, B and D.

Question 22

Where do all pathways converge?

Answer 22

Proteolytic activation of C3 to C3b.

Question 23

C3b

Answer 23

Binds to complement receptor on phagocytes, opsonises pathogens and removes immune complexes.

Question 24

C3a and C5a

Answer 24

Peptide mediators of inflammation and phagocyte recruitment.

Question 25

Terminal complement components

Answer 25

Complement proteins C5b and C6-C9, which can assemble to form the membrane-attack complex on cells coated with complement.

Question 26

Where are classical and lytic pathways seen?

Answer 26

Jawed vertebrates only.

Question 27

What happens to newly synthesised C3?

Answer 27

It is cleaved to generate a beta chain and alpha chain joined by disulfide bonds, exposing a reactive thioester bond in C3b with C3a released.

Question 28

Cnidaria immune system

Answer 28

C3-like molecules and phagocytes for defence, clonal animals can attack individuals of different genetic clones while avoiding self.

Question 29

Nematoda immune system

Answer 29

No complement pathway, pattern recognition with constitutive components such as anti-microbial and digestive peptides and inducible components like cytokines, signalling and apoptosis.

Question 30

What pathways do invertebrate chordates have?

Answer 30

Lectin and alternative.

Question 31

Fish complement activation

Answer 31

Multiple C3 isoforms, have a 2 chain structure with catalytic residue variations providing different affinity for different substrates, specialisation to bind specific surfaces and increase efficiency to eliminate microbes.

Question 32

What fish have 3 C3 isoforms?

Answer 32

Trout, medaka and zebrafish.

Question 33

What fish have 5 C3 isoforms?

Answer 33

Seabream and carp.

Question 34

Fish bacteriolytic and haemolytic activity

Answer 34

Higher than mammals.

Question 35

What is the primitive complement system?

Answer 35

Alternative pathway with C3 and Bf.

Question 36

What animals have no complement genes?

Answer 36

Flies and worms.

Question 37

What allowed for classical pathway development?

Answer 37

Vertebrate specific complement gene duplications among C3/4/5 and between Bf/C2 and MASP/C1r/s occurred.

Question 38

What provides immune cell diversity in mosquitoes and flies?

Answer 38

Dscam with many Ig domains which is diversified via alternative splicing.

Question 39

Cellular and humoural response in fish

Answer 39

Generative and secondary lymphoid organs found in mammals also found in fish, except lymph nodes and bone marrow which are replaced by the head kidney.

Question 40

Head kidney of fish

Answer 40

Haematopoietic function, phagocytosis, Ag processing, hormones and IgM.

Question 41

How many Dscam isoforms are there?

Answer 41

38,000.

Question 42

Where has somatic hypermutation been seen?

Answer 42

In animals up to land snails, which use FRP in the haemolymph.

Question 43

Mucus

Answer 43

Important barrier with freshwater fish producing more mucus with an increase in stress, contains trypsin-like cathepsin proteases, lysozyme and lectins.

Question 44

Where are fish lymphoid tissues?

Answer 44

Distributed around skin, gills and intestine to complement epidermal secretions.

Question 45

Fish thymus

Answer 45

Produces T cells involved in allograft rejection and antibody production by B cells (RAG1/2).

Question 46

What affects fish thymus involution?

Answer 46

Hormonal cycles and seasonal variants, not age.

Question 47

What appears abruptly in jawed fish?

Answer 47

Ig-based adaptive immunity.

Question 48

Variable lymphocyte receptors in jawless fish

Answer 48

Do not encode complete receptors in germline, recombination of VLR gene with flanking sequences provides a full gene which can be expressed on cell surfaces or secreted.

Question 49

Key event in ancestral hawed fish immunity evolution

Answer 49

Reinsertion that interrupts V-type Ig receptor gene, followed by recombination separating RAG from TR-tagged gene segments followed by evolution resulting in complex antigen-receptor locus with somatic recombination.

Question 50

First animal to have Ig/TCR/MHC/RAG based adaptive immunity response

Answer 50

Cartilaginous fish.

Question 51

Cartilaginous fish B cells

Answer 51

Resemble CD5+ B cells.

Question 52

Cartilaginous fish T cells

Answer 52

Resemble gamma/delta T cells.

Question 53

Cartilaginous fish gene rearrangement

Answer 53

Occurs in a cluster.

Question 54

Cartilaginous fish secondary lymphoid tissue

Answer 54

Segregated into discrete B and T cell zones.

Question 55

Cartilaginous fish MHC

Answer 55

Polymorphic Class I and Class II.

Question 56

How many VLR genes do humans have in heavy chain locus?

Answer 56

65 V, 27 D and 6 J.

Question 57

Shark heavy chain locus

Answer 57

Different configuration of VDJC repeats, regions not just sequence.

Question 58

Chicken heavy chain

Answer 58

VH pseudogenes.

Question 59

Chickens clonal diversity method

Answer 59

Unique with immature chicken B cells all produce same original heavy and light chain, then rearrangement occurs with homologous sequences in pseudogene are part of expressed Ig through somatic hypermutation.