Lecture 7- Antibodies in Infection Flashcards

1
Q

How do antigens get to secondary lymphoid organs

A

1) blood/lymphatic fluid, uptaken by dendritic cells that transport

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2
Q

Describe how foreign antigens meet the IS, through things like the skin or GI tract

A

Foreign antigens enter our system, and are meet by dendritic cells (eg- langerhans cells).
The dendritic ingest and process this material, then travels through the lymph to lymphnodes, and present this material via APC.
Here they interact with B and T cells specific to the antigen

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3
Q

What are the two classes of lymphocytes

A

Effectors : AB production (B cells, elclusively effectors), NK cells, CD8 T lymphocytes.

Regulators: Cytokine production CD4 T lymphocytes, helper T cells, regulatory T cells

NOTE T-cells are both effectors (CD8) and regulators (CD4)

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4
Q

How are shapes recognised

A

1) recognise common characteristic of many substances (non-specific immunity)
2) recognise uncommon characteristic of a particular foreign substance. (specific immunity)
3) recognise common things in uncommon context

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5
Q

Difference with what B and T cells can recognise

A

B lymphocytes = wide range of antigens

T lymphocytes = short peptide antigens

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6
Q

antibodies/immunoglobins (Ig) look like? Draw and label

A

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7
Q

How are antigen specific lymphocytes activated

A

Antigen binds > change in surface cell receptors > antigen-specific signal > alerts the cell > cell decides whether it will respond or not

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8
Q

If Bcells or T cells respond, what happens?

A

B cells > production of that same antigen specific AB

T cells > either CD8 or CD4 production

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9
Q

Epitope

A

specific part of antigen that binds to the AB

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10
Q

Primary response

A

When an animal responds to an antigen it has never previously met.
Lag of a few days (no AB able to recognise) before specific AB appear in the blood (virgin B cells will recognise and start to pump out specific AB), that can bind to the specific antigen and lead to its neutralization/ removal.

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11
Q

Secondary response

A

animal exposed to same antigen later in life, response is much more rapid and vigorous and for much longer. IS has memory B cells of this antigen, and a build up of AB

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12
Q

How do B cells generate AB response?

A

Antigens bind to surface Ig receptors on Bcells in secondary lymphoid organs. If bound with a high enough affinity they overcome activation threshold. (also extra activation by Helper T cells).
Activation of these B cells results in proliferation of
-population of memory identical to the precursor B cell that can be restimulated for a secondary response
-population of plasma cells which secretes the same antigen specific ABs.

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13
Q

Why does it take a long time for an antigen to bind to a antigen specific Bcell

A

Because although they have 1000s of receptors they are only specific to one shape, takes a long time to find a match!

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14
Q

Memory B cells

A
  • replace original B cells
  • respond to a much lower conc
  • live longer
  • there are many more

for the SECONDARY response

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15
Q

Explain the difference of our ABs in utero to post birth

A

In utero: all AB from mum, build up

Post birth: mums decline, we start to make our own, this is a vunerable period.

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16
Q

Four ways which ABs work

A

1- Direct Neutralization
2- Opsonisation
3- AB-dependent cell-mediated cytotoxicity
4- Complement activation

17
Q

Direct neutralisation

A

Coats things, physical stops the potential harm getting to where it wants to infect

18
Q

Opsonisation

A

“enhanced phagocytosis”
AB coat foreign material, and now phagocytic cells can bind with a higher affinity , increasing the effectivness of phagocytosis.

This is because the Fc region of the antibody has a high affinty for neutrophils (Fc receptors on phagocytic cells)

19
Q

Antibody-dependent cell mediated cytotoxicity

A
K cells (small pop. of lymphocytes) have Fc (AB) and C3b (complement) receptors and can kill this cellular material short range cytotoxicity.
(They are NOT phagocytic)
20
Q

Complement activation

A

Series of 20 proteins in blood that act as an enzyme cascade, that amplifies small signals.
Antigen-AB complexes can trigger the ‘classical pathway’ of this.
Results in Chemotaxis, leakage, and membrane lysis that all help to destroy/remove foreign material.

21
Q

What of the the complement system binds to antibodies and where

A

Early components at CH2 on AB

22
Q

How is the opsonisation and membrane lysis linked

A

Opsonisation provides focus fro the later complement system, that attach themselves to C3 and forma biochemical donut that inserts itself into the membrane next to C3b = cell lysis.

23
Q

Draw the classical and alternative pathway of the complement system.

A

… page 7.9