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Infection And Immunity > B Cells And Antibodies > Flashcards

B Cells And Antibodies Flashcards

1
Q

What are B CELLS

A

Found in lymphatic system
Respond to antigens by differentiating into plasma cells and producing antibodies

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2
Q

How are they activated?

A

B cells receptors bind to specific antigens.
B cells in lymphatic tissue respond to unprocessed antigens or antigens presented by APC.
B CELLS respond to foreign things by taking some of it and combine it with MHC 2.
Complex recognised by helper T CELLS.
T cells make cytokines IL 2,4,6
THEY co stimulate b cells
After activation some of b cells enlarge and become different into the plasma
Plasma secretes antibodies specific to starting STIMULATING antigen

Some b cells don’t differentiate into plasma cells but turn into memory cells

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3
Q

What are antibodies?

A

Made up of 4 polypeptides chains
2 identical heavy chains: 450 amino acids and carb chains
2 light chains: 220 amino acids

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4
Q

What is each chain bound to by?
What are two chains held by?

A

Bound to heavy chain by disulfide bond
Two chains held by: disulfide bonds which make hinge region of antibody.

Heavy chains form a common stem region

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5
Q

What do both ligh and heavy chains have in common

A

V and C regions

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6
Q

V region?

A

Specificity of antibody
Found at tips of H and I chain at apex of antibody arms

Each antibody has two antigen binding sites.
Flexibility of hinge region lets the two recognition sites bind to widely separated antigens

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7
Q

Constant C region?

A

Same in different antibodies
Has H and L chain regions not associated to antigen binding

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8
Q

C region of H chain

A

Differs between different classes of antibodies
Allows classification of antibodies in 5 different classes
Eg: IgG IgA IgM IgD IgE

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9
Q

What is a COMPLEMENT

A

Complex system of a number of SERUM PROTEINS act in a sequence

Is the major effector mechanism in humoral defence against extracellular microorganisms

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10
Q

Name complement proteins and factors

A

C1 C2 C3 C4 C5 C6 C7 C8 C9

Factor B FACTOR D and Properdin

MBP: Mannose binding protein
Some are receptors on cells and in control of sequences

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11
Q

Name complement receptors?

A

CR1,2,3

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12
Q

Complement microorganisms

A

Innate Alternative pathway: C3 B D P

LECTIN INNATE PATHWAY: MBP C4, 2

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13
Q

Complement antigen or antibody (IgM, IgG) COMPLEXES

A

Specific pathway C1 C4 C2

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14
Q

What do they lead to

A

Terminal sequence C3,5,6,7,8,9
Create biological effects

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15
Q

How does the specific pathway work

A

Antibody IgM/IgG binds to epitopes of antigen
C1 binds to FC region of antibodies
C1r activates C1s which is a proteinase
C1s cleaves C4

C4b binds to antigen
C4a remains in fluid phase

C1s cleaves C2
C2 binds to antigen, C2 remains in fluid space
C2b binds to antigen, c2a stays in fluid space

C2b cleaves C5

C2b is a proteinase cleaves C3

C3b binds to antigen C3 in fluid space
C2b cleaves C5

C5 no spontaneous binding, c5a in fluid space

C5 binds C6,7,8 in fluid phase
C5b678 bind to lipid bi layer

C9 is a pore forming protein which inserts a whole into the membrane

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16
Q

What is the microorganism lysed by

A

Membrane attack complex

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17
Q

What is the membrane attack complex

A

Complement cascade is enzymatic

Each enzyme cleaves many molecules of substrate

Lots of MAC deposited into lipid bilayer membrane of cellular antigens

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18
Q

What does the MAC form?

A

Pores in the lipid bi layer membrane of microorganism’s

19
Q

What does MAC KILL
G.E.P

A

Gram negative bacteria
Enveloped viruses
Protozoan parasites

20
Q

What do GRAM POSITIVE BACTERIA PROTECT THEM SELF FROM

A

complement mediated lysis by their thick peptidoglycan cell walls

21
Q

What do fungi protect themselves from

A

Complement mediated lysis C.M.L by thick chitin cell walls

22
Q

Is there any cell lysis for gram-positive microorganisms?
At which cleavage does the pathway end?

A

No cell lysis
At C5

23
Q

Other biological effects?

A

Complements have important role in elimination from body
From complement cleavages: C3A,5A, C3b

24
Q

What are C3A and C5a?
What do they activate?

A

Anaphylatoxins and chemotaxis
Activate mast cells and attract phagocytes (NUETROPHILS and MONONUCLEAR phagocytes)

25
Q

What is C3B and what does it enable phagocytes to do?

A

Opsonin
Enables phagocytes to recognise, bind to antigens and phagocytose them

26
Q

How does opsonisation of C3B WORK?

A

Microbe phagocytosis enhanced by interaction of C3B with C3B receptor (CR1) on phagocyte

27
Q

What is the alternative pathway?

A

Doesn’t have antibodies so it’s innate immunity

28
Q

What does it have between microbial surface polysaccharides and factors B, D, P?

A

Interactions which activate complement proteins C3
Activates ENZYME CASCADE

29
Q
A

Same biological activity generated: MAC, C3A and C5a
Opsonisation by C3b

30
Q

Recognition of xenografts- hyperacute rejection

A

Mediated by natural occuring antibodies to:
alpha Gal:
gala 1
3galb 1
4GlcNAc
Carbohydrate residue present on:
- cell surface of glycoproteins
- glycolipids on animal cells

31
Q

What is alpha Gal synthesised by

A

A1 3 Galactosyl transferase

32
Q

As humans don’t express a-Gal epitope what do they recognise it as?

A

Foreign

33
Q

What is induced by cross-reactive microbial antigens in the gut?

A

High titres of antibodies to the a- gal epitope

34
Q

What is induced by cross-reactive microbial antigens in the gut?

A

High titres of antibodies to the a- gal epitope

35
Q

What happens when a patient receives an organ graft like a kidney with its own capillary network?

A

Antibodies enter the donor blood vessels
Bind to a- gal epitopes and endothelial cells

Complement is activated
Neutrophils attracted to site, Endothelial cells destroyed

Thrombus formation blocks vessel

Organ is deprived of oxygen dies

36
Q

Immune rejection of xenogeneic tissues

A

Hyper acute preformed antibodies to gal-a1,3 gal epitope

Acute -direct pathway of immune recognition
incompatible MHC class 2 on animal cells

  • direct pathway of immune recognition; incompatible MHC CLASS 1 ON animal cells
37
Q

What does it do?

A

Removes cells from pig tissues that are not immunogenic

Extracellular matrix components such AS COLLAGEN, ELASTIN AND GLYCOSAMINOGLYCANS are similar in animals like pigs closer to man

38
Q

Immunological memory

A

T and B CELLS stay after immune response

Can proliferate quickly if re encounter same antigen

Measure of immunological memory is the antibody titre.

39
Q

What happens after getting into contact with a New antigen?

A

Steady increase in the antibody titre

First IgM then IgG
Antibody titre steadily decreases after

40
Q

What happens to the memory cells if re encountered with the same antigen?

A

Initial contact = primary response

Memory cells activated on second encounter = secondary response = memory cells quickly proliferate and make IgG ANITBODIES

41
Q

What is AGING and IMMUNITY?

A

Increased susceptibility to disease and infection with age.
Due to low levels of immune function
T cells= less responsive to antigens= less response to infections

42
Q

Why does this happen?

A

Atrophy of thymus
Less production of thymic hormones
Decrease in T CELL PRODUCTION AND B CELLS

43
Q

What happens because of reduced T and B cells production

A

Antibody titre doesn’t increase rapidly in older people

Infection And Immunity (8 decks)

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