Regulation of lymphocyte responses Flashcards
What is hypercytokinemia and sepsis?
When there is too much immune response
Too much cytokines in the blood
Sepsis – bacteria has crossed the mucosa and entered the blood stream
What are the two general principles of regulating the immune response?
Responses against pathogens decline as the infection is eliminated – this is driven by apoptosis of lymphocytes
Immunological tolerance to persistent antigens
Define Immunological Tolerance.
Specific unresponsiveness to an antigen that is induced by exposure of lymphocytes to the antigen
What are the two types of tolerance?
Central tolerance – destroy self-reactive B and T cells before they enter the circulation
Peripheral tolerance – destroy self-reactive B and T cells that do reach the circulation
What gene allows thymic expression of all the body’s gene products?
AIRE – autoimmune regulator
What does this gene encode?
Specialised transcription factor – allows thymic expression of all the body’s gene products
What are the four main mechanisms of peripheral tolerance?
Anergy
Deletion
Ignorance
Regulation
Describe each of the four processes.
Anergy – the way in which the APC presents the antigen shuts down the T cell and makes it unresponsiveness (sort of like increasing the activation energy by denying it of costimulation)
Deletion – antigen-induced cell death (apoptosis of T cell)
Ignorance – in some immuneprivileged sites there aren’t any APCs for the T cells to bind with
Regulation – regulation of response by cytokines released by Treg
What cytokine is frequently involved in shutting down dendritic cells?
IL-10
What transcription factor do Tregs express that is key to its function?
FoxP3
What are the two types of Treg?
Natural Tregs (nTreg) – develop in the thymus Inducible Tregs (iTreg) – when exposed to APCs they turn from T helper function to Treg function
