Overview of The Adaptive Immune System Flashcards
What is the functions of the adaptive immune system
- More potent
- Specific
- Memory function
- less easy to evade
Why do we have an adaptive immunity
- Protection from and defence against pathogens
- Also role in malignancy surveillance
- Also linked to damage healing and repair
How are pathogens recognised
- Generic recognisable features - TLS, PAMPs
- Presence associated with damage
- Same pathogen is seen before
- If not self cells
How does adaptive immunity prepare for unseen pathogens
- Cells have receptors for all possibilities in hopes one receptor matches with a pathogen of interest
What is the problem associated with having a massive array of possibilities approach to immunity
- Can cause autoimmune responses against self cells
- Arthritis, MS
What is the primary purpose of the immune system
- Protection from and defence against pathogens
- The same pathogens often come back and attack again - Opportunity to have effectors ready which are specific and potent
- Some pathogens stop around - Need controlling by effectors
- The effectors are primarily lymphocytes
Give some examples of B cell deficiencies/ defects
- Congenital agammaglobulinaemia
- Common variable immunodeficiency (CVID)
- Novel biologics – Rituximab
Give some examples of T cell deficiencies/ defects
- Severe Combined Immunodeficiency (SCID)
- DiGeorge syndrome -thymic failure
- Acquired – HIV / Chemotherapy / Novel biologics
Describe the multidimensionality model for defining lymphocytes
- There aren’t just different types of lymphocytes but also different dimensions
What dimensions are used to define lymphocytes
- Morphology
- Lineage
- Location
- Differentiation
- Function
How does adaptive immunity work
Has 2 key features:
- Specificity
- Memory
The pivotal role of clonal selection:
- One clone - one specificity
- Progeny can be expanded and retained
What is the basic principle of specificity for B cells and T cells according to the provided information?
- Defined by their antibody
- Ig for B cells and T cel receptors for T cells
What are the long-term protective mechanisms employed by both B cells and T cells, and how do these contribute to secondary immune responses?
- Continued production of antibody (B cells / Plasma cells)
- More rapid specific secondary responses (B and T cells)
Describe the structure of a B cell receptor
- Antigen-binding site
- Light chain
- Heavy chain
- Transmembrane region
What is required for T cell receptors (TCRs) to detect a peptide sequence from pathogens?
- Detect peptide sequence in association with MHC.
TCR doesn’t go fishing in the extracellular milieu, the pathogen peptides needs to be processed and presented to it
What cells Recognise what receptor
- CD8 T cells recognise MHC-1 through their TCR, all cells
- CD4 T cells recognise MHC-2 through their TCR, only specialised antigen presenting cells
How are T cells selected in the thymus
- Positive selection - must bind MHC
- Negative selection - Must not bind self peptides
What happens to T cells after the thymus
Naive T cells recirculate the blood and lymph nodes for future infection
Describe T cell differentiation
T cells can differentiate to carry out different functions either:
- Lymphoid homing proliferation potential self-renewal multi potency
- Peripheral homing effector function antigen dependance
Describe T cell’s memory heterogeneity
Central Memory:
- Tcm - CCR7+, CD62L+
- Enter LN and recirculate
Effector Memory
- Tem - CCR7-, CD62L-
- Migrate into tissues
- Rapid effector activity
- Cytolytic, Cytokines
Describe the central and effector memory kinetics of TEM: Effector Memory Cells
- Short-lived population
- Continually replenished
- Doubling time about 15 days
Describe the central and effector memory kinetics of TCM: Central memory cells
- Turnover at a significant rate
- Doubling time about 48 days
Describe the central and effector memory kinetics of Treg: Regulatory T-cells
- Very dynamic
- Control the responses of other T cells
How are B cells selected for
- Positive selection
- Receptor editing
- Negative selection
- Transition to IgM+ IgD+ mature B cell
- Antigen recognition leads to proliferation/differentiation
- Activated B cells transform into Plasma cells
Describe the anatomy of lymphocytes
- Organised Mainly into lymph nodes
- Key role of spleen in antibody generation
