Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cellular Basis of Immunity > Lecture 5 - Antibody molecules > Flashcards

Lecture 5 - Antibody molecules Flashcards

What are they? How are they made? Structure Classes Antibody-antigen interactions Complement

1
Q

What are antibody molecules?

A

Host proteins produced in response to the presence of foreign molecules in the body.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What cell type are antibodies primarily synthesised by?

A

Plasma cells (lymphoid lineage) and are components of the adaptive immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do antibodies bind?

A

Antigens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are antibody-antigen complexes removed from circulation?

A

Primarily through phagocytosis by macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What did Linus Paling’s model propose?

A

preformed undifferentiated ‘immunoprotein’ folded over the antigen at different locations at different haptenic groups

He also proposed that a single immunoprotein reacted with all antigens but its conformation was different in each case.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What did Sir Frank MacFarlane Burnet propose in 1959?

A

That Pauling’s model was wrong

He proposed the ‘clonal selection theory’ of acquired immunity

He realised that during the immune response certain cells were selected for antibody production

Proposed that somatic mutation during embryonic life generates the random specificities of antibodies, that cells possess concordant antigen receptors, and that cells to self -antigens are killed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 3 steps in the process of clonal selection?

A

1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce immature lymphocytes with many different antigen receptors.
2) Those that bind to antigens from the body’s own tissues are destroyed. (clonal deletion)
3) The rest are allowed to mature into inactive lymphocytes, and multiply by clonal expansion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does clonal selection achieve?

A

Detection and removal of self reactive lymphocytes, which cooked lead to conditions such as autoimmunity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 8 steps in the process of induction of B cell AB response by T cells?

A
  1. Germinal centres where b cells proliferate and undergo both isotype switching and somatic hypermutation, form within the B cell follicles in lymphoid organs
  2. This starts when DCs display antigen on their surface and activate cd4 t cells
  3. These proliferate and mature into effector cells capable of activating antigen specific b cells
  4. B Cell proliferates to form a primary focus of antigen specific b cells
  5. B cells migrate to follicles and proliferate
  6. These undergo somatic mutation, introducing new variation into the b cell receptor
  7. They then undergo a selection process: tested on their ability to bind antigen
  8. Those that don’t die undergo isotype switching – IgM-IgG…
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the structural and functional features that are shared across families of antibodies?

A

Functional - able to bind both to antigens and to specialised cells or proteins of the immune system

Structural - composed of one or more copies of a characteristic unit that form a Y shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define antigen

A

Molecule or part of molecules recognised by the variable antigen receptors of lymphocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define epitope

A

Also known as antigenic determinant, it is the specific region of the antigen bound by the variable region of an immunoglobulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define paratope

A

the antigen-binding region of an antibody

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define affinity

A

the measure of the strength of the binding of an antigen by an antibody.
The binding of an antibody by an antigen is non-covalent and reversible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the equation that describes the relationship between the affinity of an antibody for an antigen?

A

Kforward
[Ab] + [Ag] [AbAg]
Kbackward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many polypeptides does each Y shape AB contain?

A

4

2x identical heavy chains
2x identical light chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the 4 polypeptide chains of an antibody held together by?

A

Disulphide bridges and non covalent bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the role of the Fc region of an antibody and where is it located within the structure?

A

Speaks to cells of the immune system or binds to compliment

It is located at the bottom (the ‘stem’) of the Y shape (constant region)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the role of the Fab region of an antibody and where is it located within the structure?

A

Binds to the target antigen

It is located at the top two ‘arms’ of the Y shape (variable region)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What process allows alteration of the structure of the heavy and light chains in the AB variable region?

A

Somatic hypermutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are CDRs?

A

Complementarity determining regions, they are able to exhibit hyper variability, giving the AB specific finite binding capability to the target antigen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What did Rodney Porter and Gerald Edelman demonstrate?

A

Both worked on the structure of IgGand showed that:

Porter - using proteolytic fragmentation with an enzyme, showed g-globulin consisted of 3 fractions (Fab and Fc fragments)

Edelman - Showed IgG consists of 4 chains, a pair of heavy and light coins giving a Y shape configuration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the 5 main classes of AB in serum?

A

IgG, IgM, IgA, IgE and IgD

24
Q

How many different classes of heavy chain polypeptide are there?

A

five (g, u, a, e and d)

25
Q

How many different classes of light chain polypeptide are there?

A

two (kappa or lamda)

26
Q

How many sub classes does IgG have?

A

four (IgG1, 2, 3 and 4)

27
Q

How many sub classes does IgA have?

A

two (IgA1 and IgA2)

28
Q

What is the role of a J chain?

A

Holds antibody structure into a pentamer or dimer (IgM and IgA)

29
Q

What is the role of a secretory component?

A

Allows movement of the antibody out of the bloodstream into the mucosa (IgA)

30
Q

What are the roles of secretory IgA?

A

The most prevalent Ig in mucosal secretions, it binds antigens and prevents the uptake of bacteria and toxins.

31
Q

How do epithelial cells in the intestine mediate the transfer of dimeric IgA to the intestinal lumen?

A

Via the polymeric Ig receptor

32
Q

What are the 5 steps of transport of IgA across the epithelia?

A
  1. IgA dimer with J chain attached binds to the polymeric Ig receptor
  2. Binding of IgA induces transcytosis of the polymeric Ig receptor
  3. Complex is delivered to the apical surface of the epithelial cell and into the lumen
  4. Proteases cleave the pIgR near the membrane, releasing the majority of the extracellular domain still bound to IgA dimer
  5. The ‘secretory component’ protects IgA from proteases present in mucus and anchors IgA at the desired location
33
Q

What is the polymeric Ig receptor?

A

A transmembrane protein expressed at the basal surface of epithelial cells of the gut, airways and various secretory glands

34
Q

After opsonisation with IgA, which receptor mediates the uptake of organisms by macrophages and dendritic cells?

A

Fca/uR

35
Q

After opsonisation with IgA. which receptor mediates the uptake of organisms by neutrophils?

A

FcaRI

36
Q

Which class of immunoglobulin can compensated for IgA in immunodeficient patients?

A

IgM can also bind polymeric Ig receptor, and opsonise pathogens for phagocytosis via Fca/uR

37
Q

What mechanism do activating Fc receptors signal through?

A

ITAMs

38
Q

Which molecules and cell types signal through ITAMs?

A

Antigen receptors, Fc receptors and some of the captivating receptors of NK cells

39
Q

What is the ITAM signalling mechanism dependant upon?

A

A conserved amino acid sequence motif

40
Q

What does the ITAM motif consist of?

A

Two precisely placed tyrosine within a consensus sequence.
When phosphorylated the tyrosine residues provide a binding site for one or two closely related intracellular tyrosine kinases.
These have AH2 domains spaced at exactly the right distance apart to dock onto two phosphotyrosines and that activate signalling events downstream of the receptor

41
Q

What is the general principle behind ADCC?

A

Antibody dependant cell mediated cytotoxicity- antibody attracts cytotoxic cells by means of their Fc receptors

42
Q

What is the general principle behind CMC?

A

Complement mediated cytotoxicity- Antibody binding results in the fixation of complement onto the target cell

43
Q

What sort of responses does complement mediate?

A

Triggering inflammatory responses
Attraction of phagocytes to sites of inflammation
Degradation of membranes or virus envelopes
Stimulation of AB production

44
Q

What are the names of the 3 pathways that activate complement?

A
  1. Lectin pathway
  2. Classical pathway
  3. Alternative pathway
45
Q

What happens to trigger the lectin complement pathway?

A

Recognition of carbohydrate moieties e.g. by collecting such as mannose binding lectin

46
Q

What happens to trigger the classical complement pathway?

A

AB binding to antigen in immune complexes

47
Q

What happens to trigger the alternative complement pathway?

A

Occurs directly at microbial cell surfaces

48
Q

What is the purpose of the ‘early events’ of the complement cascade (what does it generate)?

A

Generates two functionally
equivalent forms of a protease, known as C3 convertase.

C3 converts can then initiate late events to produce effector components of complement.

49
Q

What are the 5 steps of the lectin complement pathway?

A
  1. AB binds microbial surface carbohydrates
  2. MASP-2 cleaves C4, C4b attaches to the cell surface and C2 binds C4b
  3. MASP-2 cleaves C2 bound to C4b
  4. C4bC2b and C3bBb C3 converts cleave C3
  5. C3 forms C3a and C3b which go on to produce effector actions.
50
Q

What are the 5 steps of the classical complement pathway?

A
  1. AB binds pentraxins or antigen-AB complexes
  2. C1 cleaves C4, C4b attaches to cell surface and C2 binds C4b
  3. C1 cleaves C2 bound to C4b
  4. C4bC2b and C3bBb C3 converts cleave C3
  5. C3 forms C3a and C3b which go on to produce effector actions.
51
Q

What are the 5 steps of the Alternative complement pathway?

A
  1. C3b binds microbial surface
  2. B binds to C3b
  3. D cleaves B bound to C3b
  4. C4bC2b and C3bBb C3 converts cleave C3
  5. C3 forms C3a and C3b which go on to produce effector actions.
52
Q

What are surfactants?

A

Phospholipids and proteins that layer and lubricate the epithelium of the respiratory tract

53
Q

What are SP-A and SP-D?

A

Surfactant protein A and Surfactant protein D - collections that function as opsonins, coating microorganisms and stimulating their uptake by phagocytosis

54
Q

What is mannose binding lectin?

A

Also part of the collection family, it binds to mannose containing carbohydrate on the surface of viruses, bacteria and fungi

55
Q

What do ficolins bind to?

A

N-acetylglucosamine

Cellular Basis of Immunity (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions