Invertebrate Immunity

Question 1

What are the two types of immunity?

Answer 1

Innate immunity and acquired immunity.

Question 2

What is innate immunity?

Answer 2

The main defensive mechanisms found in invertebrates. It is naturally present and not due to prior sensitisation to an antigen from a infection or vaccination. It is nonspecific.

Question 3

What is acquired immunity?

Answer 3

Immunity that develops with exposure to various antigens.

Question 4

What are the three attributes of an immune system?

Answer 4

Reconnaissance, Recognition and Response.

Question 5

What is the first layer of immune defence?

Answer 5

The skin, which blocks most pathogens.

Question 6

What is the second layer of immune defense?

Answer 6

Physiological, where conditions such as temperature make the bodily environment more hostile for pathogens, e.g. stomach acid. Bivalves can rapidly change the pH of their mantle fluid, which pathogens cannot deal with.

Question 7

What is the third layer of immune defence?

Answer 7

The innate immune system, consisting of roaming scavenger cells such as phagocytes which engulf pathogens and debris. Phagocytes are only able to self & non self. Motivated strongly by metabolism.

Question 8

What is diapedesis?

Answer 8

When phagocytes migrate to an outer layer of the body and ‘spit out’ debris, so it is eliminated from the organism.

Question 9

What is the fourth layer of immune defences?

Answer 9

The adaptive immune system, which consists of cells called lymphocytes that adapt to the structure of pathogens to eliminate them efficiently.

Question 10

Why is the adaptive immune system called adaptive?

Answer 10

Because antibody shapes are tailored to the 3D shapes of different pathogens.

Question 11

When did the first T and B cells appear?

Answer 11

In the placoderms.

Question 12

What is the immune systems of the Porifera like?

Answer 12

They have carbohydrate–based self–recognition and can aggregate their own cells, organising them through intercellular signalling, eventually binding them together using proteins such as fibronectin. Capable of reacting to non–self material & enhanced allogenic rejection.

Question 13

How do Porifera react to non–self material?

Answer 13

They can deactivate non–self material by initiating melanin synthesis and using exopinacocytes and mesohyl (granule–bearing) cell types for endocytosis and lysozome release.

Question 14

What is melanin synthesis?

Answer 14

A defence system used throughout the invertebrates. Melanin is a disinfectant and when pathogens are coated they can be disinfected and in sufficient concentrations can even kill them.

Question 15

What is the immune systems of the Coelenterata like?

Answer 15

They show self and non–self recognition, complex cell signalling and phagocytic activity, as demonstrated by would healing. They produce non–specific antimicrobials e.g. oxygen radicals & antifungal(chitinase)/bacterial extracellular enzymes.

Question 16

How do the Coelenterata deal with non–self material?

Answer 16

Some gorgonians can isolate/inactivate foreign material by melanisation (black spots), & chitinase as most fungi have chitin in cell walls.

Question 17

What are oxygen radicals?

Answer 17

Powerful nonspecific disinfecting agents. Oxygen radicals are disruptive, and disrupts biological molecules. They are formed from peroxidase activity.

Question 18

What is the immune system of the Annelids like?

Answer 18

They have developed cellular immunity against pathogens, including phagocytosis, encapsulation and spontaneous cytotoxicity of coelomocytes against allogenic or xenogenic cells. They also have humoral immunity that is based on antimicrobial, haemolytic and clotting properties of their body fluids.

Question 19

What is encapsulation?

Answer 19

Circulating phagocytes surround and isolate the foreign material if unable to enzymically destroy it.

Question 20

What is humoral immunity?

Answer 20

Immunity based in body fluids.

Question 21

What is the immune system of the Mollusca like?

Answer 21

They have well developed self & nonself recognition that can be locally suppressed in brooding bivalves. They can produce lectins to bind to nonself material, preparing it for phagocytosis. Humoral antiviral activity has been found in some spp, and there is nonspecific antimicrobial superoxide activity.

Question 22

What are lectins?

Answer 22

They are proteins that bind to pathogens and fix them in lace & stimulate their phagocytic response.

Question 23

What is B–hyalinocyte?

Answer 23

It contains lots of endoplasmic reticulum, which produce metabolic enzymes which produce superoxides & get a respiratory burst. They secrete huge amounts of hydrogen peroxide & bring in phagocytes bc of messenger molecules in debris of pathogen & hyalinocytes.

Question 24

What is the immune system of the Arthropoda like?

Answer 24

They have a well developed innate humoral antiviral and antibacterial agents, wound repair systems that make use of exoskeletal formation systems and toll–like receptors for pathogen recognition. Some crustaceans have primitive immunological memory, with enhanced antibacterial response on second exposure and strain specific immunity passed to offspring in Daphnia magna.

Question 25

What are toll like receptors?

Answer 25

Proteins that are specific mostly to pathogens. They are used to recognise self and nonself via PAMP.

Question 26

What are PAMPS?

Answer 26

Pathogen Associated Molecular Patterns.

Question 27

What uses does the Limulus haemolymph have in human medicine?

Answer 27

It exhibits an extreme agglutination reaction when exposed to bacteria or even minute traces of bacterial endotoxins. It is therefore used to test the purity of intravenous saline & other medical media.

Question 28

What is LAL?

Answer 28

Limulus amoebocyte lysate.

Question 29

Why does Limulus haemolymph agglutinate when exposed to bacteria?

Answer 29

The agglutination is produced by the degranulation of amoebocytes.

Question 30

What are the immune systems of the Echinodermata like?

Answer 30

They have a well developed innate immune system that includes complement proteins analogous to the C3 proteins in vertebrates. There is also some evidence of an immunological memory (enhanced allogenic rejection) similar to acquired vertebrate immunological memory.

Question 31

What are the immune systems of the Chordata like?

Answer 31

Studies of tunicates shows well-developed self & non-self recognition, e.g. in colonial ascidians adjacent clone colonies will fuse but non-related colonies will produce lesions where they meet. They have non-specific TLRs and a variety of antibacterial peptides and a prophenoloxidase cascade wound response.

Question 32

What is a prophenoloxidase cascade wound response?

Answer 32

It’s activated when different receptors recognise PAMPs, which causes serine proteases to hydrolyze and activate proPAPs to PAPs. The PAPs then hydrolyze PPO, releasing PO. PO then oxidises tyrosine to DOPA, and then into quinones, which are the precursors to melanin, cytotoxic products and then encapsulation of pathogens.

Question 33

What are proPAPs?

Answer 33

Prophenoloxidase-activating proteinase precursors.

Question 34

What is PAP?

Answer 34

Prophenoloxidase-activating proteinase.

Question 35

What is PPO?

Answer 35

Prophenoloxidase.

Question 36

What is PO?

Answer 36

Phenoloxidase.

Question 37

What is DOPA?

Answer 37

Dihydroxyphenylalanine.

Question 38

What are T & B Cells?

Answer 38

The cellular components of vertebrate immune systems that recognise pathogens by the shape of molecules (antigens) on their surfaces. Vertebrate immune systems can produce a T & B-cell to fit every possible shape.

Question 39

What happens to T & B cells with the ability to bind to the body’s own cells?

Answer 39

They are destroyed, because if they were left in the body the result would be autoimmune disease.

Question 40

What does a B-cell do?

Answer 40

It attacks invaders outside cells.

Question 41

What do T-cells do?

Answer 41

They attack invaders inside cells.

Question 42

What are the functions of T-cells?

Answer 42

Having recognised non-self material, they have different jobs. Some send cytokines (chemical instructions) to the rest of the immune system, activating the appropriate defence systems. Others recognise and kill infected cells directly. Some help B-cells to make antibodies.

Question 43

What are the functions of B-cells?

Answer 43

With the help of T-cells, they produce antibodies that bind to antigens on the surface of pathogens, initiating the process of inflammation, firstly immobilising the pathogens by agglutination, then stimulating phagocytic macrophages and natural killer cells to engulf and digest the antibody-marked pathogens.

Question 44

What are the two regions of an antibody?

Answer 44

Variable and constant regions. The antibody is Y-shaped, with the arms being variable and the tail being constant.

Question 45

What does the variable region of the antibody do?

Answer 45

It provides specific binding of of pathogen epitopes.

Question 46

What does the constant region of the antibody do?

Answer 46

It defines the isotype that binds to other immune system components, e.g. macrophages.

Question 47

How are pathogens detected in the vertebrate immune system?

Answer 47

Detection is a consequence of binding between complementary chemical receptors. The surface of a lymphocyte is covered in receptors, and some pathogens will have epitopes with a high affinity for receptors,allowing them to bind and be detected.

Question 48

How is receptor diversity generated?

Answer 48

“Random” recombination of gene segments generates a combinatorial number of receptor varieties.

Question 49

What is affinity maturation?

Answer 49

The selection of effective receptors. Activated B-cells proliferate, producing mutated clones, which are selected by their affinity. High affinity clones are selected to form plasma cells and produce antibodies, or become memory cells. Low affinity clones cannot bind and undergo cell death.

Question 50

What effect does immune memory have on responses to pathogens?

Answer 50

Primary responses to new pathogens take an order of weeks, whereas memory of previously seen pathogens allows the secondary response to be in a matter of days with a much larger reaction.

Question 51

How are intra-cellular pathogens destroyed?

Answer 51

Tk-cells are activated by binding to a MHC/peptide complex on a self cell and costimulated by the innate immune system will destroy the self cell that presented the MHC/peptide complex.

Question 52

What is the role of the prophenoloxidase cascade in crustaceans?

Answer 52

Responds to pathogens and tissue damage by encapsulating and melanising pathogen and/or damaged tissues.