Class notes

principles of adaptive immunity

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Course
Mechanisms of pathology

Institution
Aston University, Birmingham (Aston)

• Adaptive immunity is the third line of defence. • It happens after the physical barriers such as tears, skin mucous and stomach acid. • This is followed by innate immunity which is the immune system that is present from birth, this includes soluble mediators such as complement and cytokin...

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Uploaded on August 28, 2024
Number of pages 11
Written in 2024/2025
Type Class notes
Professor(s) Prof andre devitt
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principles
adaptive immunity
biomedical science
aston

Institution
Aston University, Birmingham (Aston)
Education Unknown
Course
Mechanisms of pathology

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Mechanisms of pathology (MOP)

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1. Class notes - Innate immunity
2. Class notes - Principles of adaptive immunity
3. Class notes - Antibody structure and b cells
4. Class notes - Antigen processing and presentation
5. Class notes - Antigen recognition by t cells
6. Class notes - Defence against infection
7. Class notes - Failures of defence
8. Class notes - Hypersensitivity
9. Class notes - Autoimmunity
10. Class notes - Tumour immunology
11. Class notes - Gram positive staphylococci
12. Class notes - Clinically significant fungi
13. Class notes - Mycobacteria
14. Class notes - Gram negative facultative anaerobes
15. Class notes - Neisseria
16. Class notes - Chlamydia
17. Class notes - Viral infection
18. Class notes - Gram positive spore forming rods
19. Class notes - Nematodes
20. Class notes - Antibiotics
21. Class notes - Cell death
22. Class notes - Inflammation in pathology
23. Class notes - Prion disease
24. Class notes - Parkinsons disease
25. Class notes - Dna structure
26. Class notes - Cml and imatanib
27. Class notes - Tumourgenesis
28. Class notes - Breast cancer
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Principles of adaptive immunity

Part 1 pathogen recognition.

 Adaptive immunity is the third line of defence.
 It happens after the physical barriers such as tears, skin mucous and stomach acid.
 This is followed by innate immunity which is the immune system that is present from
birth, this includes soluble mediators such as complement and cytokines in the
blood. And also includes a number of cell types that it can immediately recognise
and attack pathogens after they have infected our body.
 Adaptive immunity
 Requires different types of cells specifically the lymphocytes such as B and T cells.
 They have similar effective mechanisms to innate immunity but they have a unique
system of recognition that leads to a very specific response.
 These cells also have the capacity to develop memory.
 They stick around and are in place to protect us if we are infected with the same
pathogen again.

Pathogen recognition-innate immunity
 Pathogen recognition in innate immunity is the fixed repertoire of cells and soluble
molecules.
 So these are pathogen recognition receptors, such as TLR-4 (This is the PRR that
recognises LPS)
 All of these components are inherited, they are in place at birth, and new variants
very rarely arise.
 The overall strategy is to recognise broad non-differentiating pathogenic structures
or to detect alterations in infected or damaged cells.

Pathogen recognition- adaptive immunity
 Pathogen recognition in adaptive immunity is very specific.
 Each lymphocyte (T-cells and B-cells) expresses just one type of molecular receptor
with a single specificity.
 B-cells express the B cell receptor (AKA BCR or membrane bound immunoglobulin)
 T cells express the T cell receptor
 These receptors are made by gene rearrangements so they get jumbled up so we
have millions of different specificities.
 Each cell is a clone that expresses a unique and specific receptor. That only
recognises one epitope of a pathogen.
 Advantages of adaptive immunity:
 Precise targeting- immune system is only going after the main thing that has infected
you.
 Memory cells- it is able to generate memory cells
 It is also able to recognise new pathogens- pathogens do change what they look like
over time to evade the immune system and the adaptive immune system is capable
of responding to this.

Receptors of adaptive immunity

,  Receptors of adaptive immunity are antibody
 When it is expressed on the surface of a B cell it is called a B cell receptor.
 Every B cell only produces one of these antibodies.
 A B cell expresses surface immunoglobulin.
 The immunoglobulin have a transmembrane region
 whereas Plasma cells which are a more matured form of B cells, they just produce
antibody for secretion into the extracellular space.
 Plasma cells produce a secreted antibody and no longer express the antibody on the
cell surface.
 T cells
 They express a T cell receptor with an alpha and beta chain.
 This is always on the cell surface receptor and is ready to recognise antigen.
 The T cell receptor has a constant region towards the cell membrane and the distal
site at the very end of the molecule, that is where the very specific antigen binding
site is.
 The antigen binding site recognises a specific epitope or protein fragment from a
specific pathogen and each one of these T cells or B cells produces one kind of this
receptor.
 In the antibody B cell molecule, we have a constant region, this stays the same
depending on which class of antibody you are talking about.
 The antigen binding site is at the ends of the Y shaped arms of this molecule and that
is the specific region of that molecule that can detect a particular epitope of a
pathogen.

Receptor diversity is generated by gene rearrangement
 this receptor diversity is generated by gene rearrangements.
 There is a germline configuration of genes that encodes for the B cell and T cell
receptors that cannot be transcribed.
 These need to undergo a nucleotide insertion and rearrangement to allow
transcription to happen.
 And whilst this happens certain segments are chosen.
 Gene rearrangement happens differently in every clone.
 Every different lymphocyte undergoes its own unique type of rearrangements of
these genes to produce a unique T cell or B cell receptor.

Receptors of adaptive immunity are highly specific
1. During development, progenitor cells give rise to large numbers of circulating
lymphocytes, each having a different form of cell-surface receptor.
2. The receptors of only a few circulating lymphocytes interact with any given
pathogen.
3. Pathogen reactive lymphocytes are triggered to divide and proliferate.
4. Pathogen-activated lymphocytes differentiate into effector cells that eliminate the
pathogen.
 During development the progenitor cells give rise to a large numbers of circulating T
cells.
 You have many different types of T cells and B cells. So lots of different circulating
lymphocytes and each of these has a different cell surface receptor.

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