Lecture 14: adaptive immune response

The innate response specificity is - - - - - - -

The innate response specificity is - - - - - - -

Limited

Where is the innate immune response found

In all tissues (especially at barrier sites)

How long is the innate responses memory

Limited

Specificity of the adaptive response

Specific for particular proteins / antigens

How long is the adaptive response memory

A long lived immune memory

Where does the adaptive response get information from

The innate response

What is the spike protein

An example of an antigen: on the surface of a virus and is used to get into cells

What happens when the immune system recognises an antigen

An immunological response is produced

What is the antigen or epitope

When protein antigens are broken down to form peptide chains of around 8 peptides

What are B and T cells

Adaptive immune cells which specifically recognise antigens via specialised surface receptors

How many different B cell receptors are there

Up to 10^12

How many different T cell receptors are there

Around 10^8

Where are B cells specialised

Bone marrow

What is each B and T cell receptor specific to

One particular different pathogen

Where are T cells specialised

Thymus

How does a B cell produce a response

The B cell receptor binds to its specific antigen without the need of accessory cells

What are the 2 types of T cell

CD4, CD8

Which class of molecules do CD4 T cells recognise

Longer peptides in MHC class II

What class of molecules do CD8 T cells recognise

Short peptides in MHC class 1

How do T cells produce a response

T cells recognise the processed antigen presented on MHC molecules on the surface of antigen presenting cells

Example of an antigen presenting cell

Dendritic cells

What do T cells need to produce a response

Accessory cells

Where are adaptive immune cells activated

Secondary lymphoid organs: spleen & lymph nodes

How do T cells travel to the infected site

Use blood in the lymphatic system

Stages of the adaptive immune response

1. Finding & activating the right T & B cells

2. Pending the best response & responding

3. The immune response (attacking pathogen)

Timings of the immune response

1. Day 0-5 = innate

2. Day 3-15 = adaptive

3. Months - years after = long lived immune protection

What are plasma cells

Long living B cells which will continue to make antibodies which protect against the same pathogen

When are the adaptive immune cells alerted

If the infection is not mild and the innate immune cells cannot clear the pathogen themselves

Direction of immune response information transfer

Pathogens → innate cells → adaptive cells

What will complications in the transfer of information cause

The wrong immune response

What are antibodies made by

Plasma cells

IgM molecules

• Low affinity antibody

• High avidity

• Good for extracellular viruses

IgG molecules

Most abundant in serum

IgE molecules

Involved in allergy and anti-helminth worm responses

IgA

Found at mucosal sites

What is a somatic hyper mutation

Mutation in the arms of an antibody to increase affinity to pathogens

3 ways antibodies act to protect host

1. Binds & neutralises the pathogen to stop it infecting host cells

2. Activate complement to enhance immune response

3. Enhance phagocytosis by binding to receptors on phagocytes which have receptors for antibodies

What cells express MHC II molecules

Professional antigen presenting cells: B cells, macrophages & DCs

What cells present MHC I molecules

All nucleated cells: B cells, macrophages, DCs, epithelial cells & fibroblasts

What type of T cell is the helper cell

CD4

How do CD4 cells help CD8 t cells

Help them make a strong response via dendritic cells & soluble molecules

How do CD4 cells help B cells

Help them generate high affinity antibodies

How do CD4 cells help macrophages

They activate macrophages to kill phagocytic pathogens more effectively

What cells can make cytokines

CD4 T cells

Role of CD8 T cells

They are cytotoxic cells which find infected cells & trigger apoptosis by releasing toxic molecules into the target cell.

What type of cells kill tumour cells

CD8

What T cells initiate the immune response

CD 4

How do memory cells work

• Perform the same function as newly activated cells however respond more quickly which stops the growth of the pathogen & reduces the chance of host illness

• Form once the pathogen has met the host or if the host has been vaccinated