Overview of The Adaptive Immune System Flashcards
What are the key points to the Adaptive Immune System?
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 immune responses?
Protection from and defence against pathogens essentially
Also role in malignancy surveillance
Also linked to damage healing and repair
The same pathogens often come back and attack again- therefore gives an opportunity to have effectors ready which are specific and potent
Some pathogens stick around so they Need controlling
If every pathogen was completely “new” and every pathogen was completely eliminated after infection, there might be no need for an adaptive immune system
How can we spot a pathogen?
1.Generic recognisable features – eg TLR – PAMP’s
2.Recognition of a pathogen if there is tissue damage
The Danger Hypothesis – co-stimulation – CD28
Damage-associated molecular pattern molecules (DAMP)- these show up damage so allows pathogen to be recognised
- recognising pathogen that has been there before
- autoimmunity-self vs non-self
How can we describe/define lymphocytes?
Defining lymphocytes:
Morphology:
White cell; small, large nucleus
Lineage:
T and B cells
Location:
Tissue-resident memory cells (TRM)
Marginal zone B cells
Differentiation:
Naïve / memory (central, effector, stem cell memory)
Immature / mature or differentiated / senescent
Function: What they do
eg Helper / Cytotoxic / Regulatory / Antibody-producing
Phenotype: What surface markers they express
Eg CD4, CD8, CD28 … Usually functional receptors–
not just there for our convenience!
Specificity
What target – What Ab produced or epitope recognised (TCR)
Type of receptor Ig class for B cells / αβ vs γδ for T cells
By what they produce
TH1 (IL-2, IFN-γ)
TH2 (IL-4, IL-5, IL-6, IL-10)
What are the two key features of the adaptive immune response?
Two key features:
Specificity
Memory
The pivotal role of clonal selection
One clone – one specificity
Progeny can be expanded and retained
Clonal selection and adaptive immunity- what is the link/what do we know?
Basic tenet – one cell / one specificity
For B cells – one cell, one Ig
Defined by their antibody
May class switch / undergo affinity maturation
but always the same basic Ig
For T cells – one cell, one T cell receptor – TCR
Selection and expansion of that clone ± differentiation
Retention in “memory” of clonal progeny
Continued protection
Continued production of antibody (B cells / Plasma cells)
More rapid specific secondary responses (B and T cells)
What precursors do B and T cells emerge from?
Common lymphoid precursors
What does TCR (t cell receptor) do?
Detects a peptide sequence in association with MHC
Pathogen peptides need to be processed and presented
The T cell receptor recognises the peptide- it does not recognise proteins so the antigen presenting cell needs to cut up the protein into small pieces and present them to the MHC molecule.
All cells process their intracellular contents and present on MHC-I
Recognised by CD8 T cells through their TCR
Crucial to defence against viruses
Specialised antigen-presenting cells (APC) process and present peptides in MHC-II
binds to TCR on CD4 T cells
For this process to work, the T cell must bind the MHC well enough to recognise the protein.
Its a 2 step process in the thymus then after the cells come out the thymus,
Naïve cells recirculate
primarily from blood to lymph nodes.
So cells for various diseases etc eg Ebola, flu etc are ‘sleeping’ waiting for an antigen to come by and ‘wake them up and then they would proliferate
What do activated B cells transform into?
Activated B cells transform into Plasma cells
“Antibody factories”
also produce CD27+ memory B cells
