Regulation of the immune response Flashcards
T & B cells generate
self-antigen receptors that must be destroyed or turned off
Regulation of adaptive immunity
- recognize & eliminate foreign invaders
- kill target cells
Tolerance
lack of immunity
Immature lymphocytes become tolerant to an antigen if they first met in fetal life. Observed in
chimeric calves
Central
-immature self reactive lymphocytes w/in thymus, bursa, or bone marrow die or alter their receptor specifity
Peripheral
mature lymphocytes that encounter self-antigens are turned off or suppressed by T reg cells
Chimera calves
fused placenta, born from same cow, NOT twins, cells migrate to eachother, grow inutero e/ contact from each other
- born with cells from other calf
- skin grafts will NOT BE REJECTED since they were in contact while maturing
What cells are more easily rendered tolerant: T or B cells?
T cells are more tolerant
Cells w/ non functional TCRs will undergo apoptosis
negative selection
Thymic epithelial cells
express many proteins from different tissues
AIRE= transcription regulator, autoimmune regulator
Positive selection
ensures that the cells that recognize self-MHC molecules survive
Recognize self antigens?
yes-apoptosis
no-negative selection
React w/ MHC?
moderately=positive selection
proliferation–> MHC restricted noneself reactive T cells
Very high or low dose of antigen cause
TOLERANCE
Moderate dose of antigens cause
antibody production
T cells require multiple signals in order to respond to antigen. If signals are insufficient, T cell response will
be surpressed
Central B cell tolerance
- VDJ rearrangement, gene conversion, somatic, mutation
- immature B cells recognize self antigens
- B cell supression @ early stages in animals development
Peripheral B cell tolerance
- absence of co-stimulation
- repeated exhaustive antigen stimulation=short-lived plasma cells, no memory cells=tolerance
- oral proteins in high doses induce clonal deletions & anergy
- oral proteins in low doses induce development of Treg cells
Central tolerance
immature B cells–> low doses of antigen –> clonal abortion
Peripheral tolerance
Mature B cells
- exhaustive antigen challenge-clonal exhaustion
- absence of costimulation-functional deletion
- excessive suppressor cell activity-functional deletion
- excessive T-independent antigen-receptor blockade
An inadequate immune response may lead to
immunodeficiency and increased susceptibility to infection
An excessive immune response may result of
allergies or autoimmunity
Antigen increased
immune response is prolonged
Antigen decreased
immune response stops
