Overview Of Adaptive Immunity Flashcards
Why do we have an adaptive immune system?
Some pathogens often come back and attack again - opportunity to have effectors ready
Some pathogens stick around - need controlling
How do we recognise pathogens?
Generic recognisable features- PAMPS
They’re presence is associated with damage - damage associated molecular pattern molecules (DAMP)
Memory of past infection
Not familiar - autoimmunity - organ rejection
What is the problems with predicting the unpredictable?
Over and under assiduous recognition
Self recognition
What is a reactivated infection?
Low CD4 count has allowed “opportunistic infection” to get through the immune defences that should control it
What are examples of diseases caused by B cell deficiency?
Common variable immunodeficiency (CVID)
What are examples of diseases caused by T cell deficiency?
Severe combined immunodeficiency (SCID)
Acquired - HIV/chemotherapy
What are the ways we can define lymphocytes?
Morphology - white cell, small, largeb
Lineage - T cell and B cell
Location - tissue resident and marginal zone
Differentiation - memory, mature, immature, differentiated
Function: what they do - helper, cytotoxic, antibody producing
What factors define a lymphocyte?
Phenotype: what surface markers they express
Specificity- what target
Type of receptor
By what they produce
How does adaptive immunity work?
Specificity
Memory
What is clonal selection?
One cell - one specificity
Describe clonal selection for B cells
One cell - one immunoglobulin (ig)
Defined by their antibody
May class switch/ undergo affinity maturation
But always the same basic ig
Describe clonal selection for T cells
One cell - one T cell receptor
Selection and expansion of that clone and differentiation
Retention in “memory” of clonal progeny
Which clonal cells provide continuous production of antibodies?
B cells
Plasma cells
Which clonal cells provide a more rapid specific secondary response?
B and T cells
What is a defining feature of a lymphocyte?
The specific receptor - variable reigons
How do antigen presenting cells express the specific antigen?
Specialised antigen presenting cells process and present peptides on MHC-1
Recognised by CD8 cells through they’re TCR
Bind to TCR on CD4 T cells
What is positive thymic selection of T cells?
Must bind MHC
What is negative thymic selection of T cells?
Must not bind to self peptides
If it binds to self proteins too much the cells die
How are naive cells maintained?
They just float around in the blood and lymph nodes
Why do naive T cells have slow turn over rates?
They remain in active until a very strong antigen binds to its receptor
Then they differentiate into other T cells
What are effector memory cells TEM?
Short lived population
Continually replenished
Doubling time about 15 days
What are central memory cells TCM?
Turnover at a significant rate
Doubling time about 48 days
How are B cells selected?
Posative/negative selection
Transition to IGN and IGD and mature B cell
Receptor editing
Activated B cells transform into plasma cells
Antigen recognition leads to proliferation/differentiation
Describe the anatomy of lymphocytes
Organised mainly into lymph nodes - archetecbture optimised to facilitate cellular interaction
What important role does the spleen play in antibody production?
Splenectomy increases risk of infection
Especially pneumococcal infection
