Overview of Adaptive Immune System Flashcards
What is the point of adaptive immune system if innate can get rid of some pathogens?
- In case same (not diff) pathogen comes back so effector cells are ready for potent response
- Latency - prevent reactivation of pathogen that wasn’t fully cleared (latent infection)
What are the 2 types of adaptive response?
Learned response (repeated pathogen) Programmed (detected damage/problem)
What things can be recognised causing an adaptive response to take place?
- PAMPs e.g flagellum recognised by TLRs
- Damage detected (DAMPs or CD28 co-stimulation)
- Reoccuring infection e.g. shingles
- Autoimmunity - self vs non self e.g. transplant
What are the cells involved in adaptive immunity?
Effector cells called primary lymphocytes
What will happen if there are no T cells?
Allows opportunistic infections such as reactivation infections that immune system otherwise would’ve been able to control
Give examples of lymphocyte deficiency (of B cells)?
Give examples of lymphocyte deficiency (of T cells)?
What are all the lymphocytes?
NK cells, B cells and T cells
only B and T are adaptive - have memory
What are the different categories to define lymphocytes?
Morphology (small/large nucleus)
Lineage (T or B cells)
Location (tissue resident memory cells or marginal zone B cells)
Differentiation (naiive or memory, immature or mature)
Function (helper, cytotoxic, regulatory)
Phenotype (surface markers e.g. CD4 or CD8)
Specificity (antibody produced or epitope produced according to TCR)
Type of receptor (Ig for B cells, alpha beta or gamma delta in T cells)
Which cytokines they produce (TH1 produces diff types to TH2 cells)
What are the 2 main features of adaptive immunity? and why are they important
Specificity
Memory
- allows clonal selection for continued and rapid protection during secondary response
What is clonal selection?
One specific type c is clones e.g B cell - produces 1 Ig and T cells produces one T cell receptor (TCR)
Where do B cells and T cell originate from?
Bone marrow
What does the receptor in B cells look like?
Surface immunoglobulin (B cell receptor) variable region, constant region AND A TRANSMEMBRANE REGION Antibody has all but transmembrane region
What does a T cell receptor have structurally?
Antigen binding site, variable region, constant region, transmembrane region (either alpha and beta chain or gamma and delta chain)
What is the structure of an antibody?
Antigen binding site, heavy chain and light chain (only a portion of heavy chain is in constant region) (both in variable region)
What do T cell receptors recognise in the antigen binding site?
Peptide sequence (that has been processed and presented) associated to a MHC molecule (in its groove)
Where are MHC class 1 molecules found? and what do they present?
On all cells - present intracellular contents
What recongises MHC class 1 molecules?
CD8 T cells T cell receptors
Where are MHC class 2 molecules found and what do they present?
Found on specialised antigen presenting cells (APC) which have processed and presented peptides
Which recognises MHC class 2?
TCR on CD4 T cells
What happens in thymic selection briefly? major stages
Positive selection of T cells - must bind to self MHC to select T cells
Negative selection of T cells - Must not bind to self peptides
Why is T cells thymic selection important?
Keep balanced amount of correct T cells
What happens to T cells after thymic selection?
Naive T cells recirculate (some into peripheral blood and some into lymph nodes)
How do we label lymphocytes?
In vivo with deuterium labelled glucose
Why are a little amount of naiive T cells found in peripheral blood?
naiive T cells have very slow turnover rates - stay naiive until activated
What are the types of memory T cells?
Central memory t cells (TCM)
Effector memory T cells
Where are central memory t cells found?
Enter lymph nodes then recirculate
Where are effector memory T cells found?
Migrate into tissues for rapid effector activity
Which are the types of T cells left after infection (no longer naiive)?
TEM (effector memory cells)
TCM (central memory cells)
Treg (regulatory T cells)
What are the steps for B cell repertoire selection?
Positive selection Receptor editing (to avoid recognising self) Negative selection Transition from IgM to IgD mature B cell Antigen recognition leads to proliferation/differentation e.g. into plasma cells, memory B cells
Where are lymphocytes mostly found? and why
not much in blood, more in lymph nodes. as lymph flows through, infected cells detected and correct B/T cell is selected for
What is the structure of a lymph nodes
B cells, T cell, macrophages and plasma cells are densely packaged
Lymph flows through vessels with valves to prevent backflow
What is the marker of tissue resident T cells?
CD69+ T cells
