Overview of The Adaptive Immune System Flashcards
What is adaptive immunity?
- The part of the immune system that has enhanced rapidity, potency or specificity as a consequence of previous events (exposure or vaccination).
- Memory is the key element
- “Anamnestic response” – not forgetting
Why have adaptive immunity?
- Protection from and defence against pathogens
- Also role in malignancy surveillance
- Also linked to damage healing and repair
How do we spot pathogens?
• Generic recognisable features – eg TLR – PAMP’s
There’s trouble going on (Their presence is associated with damage)(tissue damage)
• The Danger Hypothesis – co-stimulation – CD28
• Damage-associated molecular pattern molecules (DAMP)
• Seen the pathogen before
• Autoimmunity
What are the main drivers of the adaptive immune response
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How does the immune system set up a system to recognise things not yet seen?
• The “massive array of possibilities” approach
Why do we need effectors?
- The same pathogens often come back and attack again
- Opportunity to have effectors ready which are specific and potent
- Some pathogens stick around
- Need controlling by effectors
Give some examples of T and B cell deficiency’s
B cells
• Congenital agammaglobulinaemia
• Common variable immunodeficiency (CVID)
• Novel biologics – Rituximab
T cells
• Severe Combined Immunodeficiency (SCID)
• DiGeorge syndrome -thymic failure
• Acquired – HIV / Chemotherapy / Novel biologics
All create major, often life-threatening clinical problems
Where do lymphocytes fit in the immune response
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Describe the cells of the innate and adaptive immune system
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What are the bridging cells between the innate and adaptive immune system?
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How do we define lymphocytes?
• Morphology: o White cell; small, large nucleus • Lineage: o T and B cells • Location o Tissue-resident memory cells (TRM) o Marginal zone B cells • Differentiation o Naïve / memory (central, effector, stem cell memory) o Immature / mature or differentiated / senescent • Function: What they do o eg Helper / Cytotoxic / Regulatory / Antibody-producing
How can lymphocytes be classified?
• Phenotype: What surface markers they express
o Eg CD4, CD8, CD28 … Usually functional receptors–
not just there for our convenience!
• Specificity
o What target – What Ab produced or epitope recognised (TCR)
• Type of receptor
o Ig class for B cells / αβ vs γδ for T cells
• By what they produce
o TH1 (IL-2, IFN-γ)
o TH2 (IL-4, IL-5, IL-6, IL-10)
How does Adaptive immunity work?
Two key features:
• Specificity
• Memory
The pivotal role of clonal selection
• One clone – one specificity
• Progeny can be expanded and retained
Describe clonal selection of the adaptive immune system
• Basic tenet – one cell / one specificity
• For B cells – one cell, one Ig
o Defined by their antibody
o May class switch / undergo affinity maturation
o but always the same basic Ig
• For T cells – one cell, one T cell receptor – TCR
o Selection and expansion of that clone ± differentiation
o Retention in “memory” of clonal progeny
• Continued protection
o Continued production of antibody (B cells / Plasma cells)
o More rapid specific secondary responses (B and T cells)
Describe the lineages of T and B cells
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