W3 Immune memory Flashcards
What is the difference between a long lived plasma cell and a memory B cell?
Long lived plasma cells - consistently secrete low levels of antibodies even after the first infection is tackled, these antibodies act immediate on the second infection.
Memory B cells - must be reactivated on second infection by coming into contact with the antigen.
Where can memory cells be found?
Circulate in the blood and lymphoid tissue, log lived plasma cells often return to the bone marrow.
What is a primary immune response?
First time an individual’s immune system sees an antigen either by infection or vaccination.
What is a secondary immune response?
How is this different to a primary immune response?
When an individuals immune system sees a pathogen for a second onwards time.
The cells are antigen experienced and have immunological memory.
Response is quantitativly (amount) and qualitativly (quality) better, meaning often fewer or no symptoms.
What is meant by a safe dose of a pathogen?
Purposfully given in a manageable way, does not cause illness or death, such as a vaccine.
How long do memory cells often last?
Long lived plasma cells and antibody concentration remains at a higher level for longer, reducing by less than 25% over more than 30 years.
CD4 cells memory decreases faster reaching half life around 22 years.
CD8 cell memory is lost quicker again reaching half life at around 22 years.
How are short lived plasma cells produced?
A follicle B cell with a presented antigen is actived by a FH t-cell.
B cell proliferates and immediately some cells differentiate inot short lived plasma cells produce IgM antibody to give a faster response to infection
These plasma cells are produced before somatic hypermutation and often die later in the response by apoptosis.
How are long lived plasma cells produced?
After short lived plasma cells are produced the activated B cell enters the germinal centre, the cell undergoes somatic hyper-mutation and proliferates rapidly into large amounts.
B cells with higher affinity antibodies are activated by T helper cells hence selected for.
These will differentiate into plasma cells or memory B cells and leave the germinal centre.
When does class switiching recombination occur for B-cells?
In the germinal centre, after the production of short lived plasma cells.
During the process / before the production of long lived plasma cells.
What are some characteristics of memory B cells?
Higher affinity for antibody than plasma cells - as undergoes further somatic hypermutation and affinity maturation by re-entering germinal centres
Produces class switched antibody.
Produces antibody faster
Higher levels of MHC2 and costimulatory molecules to attract helper T cells.
What type of class switched antibody do long lived B cells produce?
IgG and IgA
What are the two different types of memory T cells?
Two types, Central and effector memory T cells
How do memory T cell develop?
Naive T cell is activated by a dendritic cell to become an effector cell.
Some effector cells directly become memory cells (no action in 1st response = anergic as cannot respond to antigen)
Some effect cells carry out their function then die by apoptosis or become memory cells by becoming quiescent (dormant).
What are some features of central memory cells?
Have a CCR7 receptor.
Remain in lymph nodes so can move to any part of the body on secondary infection.
Behave similar to naive cells.
Not commited to Th1 or Th2 cell.
Long lived precursors can take longer to respond.
What are some key features of effector memory cells?
Reside in area of tissue where first infection occured
Immediate expansion on re-infection within this site
Express receptors for inflammatory chemokines so can be recruited to inflammation sites rapidly.
Committed to a lineage, Th2 Th17 etc
Produce cytokines quickly.
Have a CCR5 receptor.
What is meant by trained imunity?
When the innate immune system shows short term memory.
Can be caused by epigentic or metabolic reprogramming to cause enhanced effector functions.
Innate cells will give a large response such as production of more cytokines, more neutrophil migration.
Based on the idea that in the short term after an innate response the body may still be in an area where is is likely to be exposed to the pathogen again.
How is the innate system trained memory different to the adaptive system memory?
Trained immunity is shorter lived and properties eventually return to normal as if the memory never occured
Adaptive memory is longer lasting and cells do not return to normal.
What type of immunity should a vaccine trigger?
Vaccines needs to trigger an adaptive immune response to produce memory B cells and hopefully memory T cells.
This means the method used must be pathogenic enough to survive the innate response but not too pathogenic to causes illness.
