2.2.1 Tolerance and Autoimmunity Flashcards
(44 cards)
Define immunogenic.
Elicits proliferation, differentiation, and effector function from lymphocytes
Define tolerogenic.
does not elicit a functional lymphocyte response (lymphocyte killed, inactivated, or no reaction at all)
Distinguish b/t central and peripheral tolerance. Where do they occur?
Central: occurs during lymphocyte development in primary lymphoid organs (Thymus and BM) Peripheral: occurs in the periphery (SLOs or non-lymphoid tissues)
What is the term for the promoting survival of T cells that recognize MHC molecules with low affinity for self-peptides?
Positive Selection
What happens to T cells that have a strong affinity for self-peptides in the thymus? Is this a perfect process?
Negative selection, not 100% effective
If cells don’t recognize MHC at all, what happens?
Death by neglect
If cells recognize MHC with strong affinity for self-peptides but survive thymic development, what is their mature cellular form? What do they contibute to?
Treg; peripheral tolerance
How do T cells specific for Ag not expressed in the thymus get negatively selected?
AIRE gene (autoimmune regulator) - induces the expression of peripheral tissue Ag by cells in the thymus
What happens if there is a mutation in AIRE?
APECED (autoimmune polyendocrineopathy-candidiasis-ectodermal dystrophy syndrome): a multi-organ autoimmunity
What are the four peripheral responses to an autoreactive T cell?
- Functional inactivation (anergy)
- Treg-mediated suppression
- Death (apoptosis)
- Ignorance
What type of signal leads to anergy?
Naive T cells recognize MHC/peptide complex (signal 1) in the absence of costimulation (signal 2) or in the presence of inhibitory signals
What is the main co-receptor on T cells involved in the signal 2 of the 2-signal theory?
CD28 (on T cell) binds B7-1/2 of APC
What are two inhibitory recepors-lignand interactions responsible for angery?
PD-1 (T cell)/PDL (APC)
CTLA-4 (T cell)/B7 (APC) blocks binding of CD28 to B7 and can deliver inhibitory signals
What are the targets of ipilimumab and nivolumab?
ipilimumab: anti-CTLA-4 Ab
nivolumab: anti-PD-1 Ab
What transcription factor is important in Treg development and function?
FoxP3
A mutation in FoxP3 leads to a lack of functional Treg, which yields mulitorgan autoimmunity. What is the acronym for this disorder?
IPEX
What interaction is responsible for lymphocyte activation induced cell death that clears effector lymphocytes?
Fas-FasL
What is the genetic cause of autoimmune lymphoproliferative syndrome (ALPS)? What are the two results of this mutation?
Mutated Fas signaling; autoimmunity and lymphocyte accumulation
What is receptor editing?
Immature B cells that recognize self Ag reexpress RAG genes, resume Ig light recombination and express a new Ig light chain
What are the three mechanisms of peripheral tolerance?
Anergy, Death (apoptosis), Ignorance
How is Ig concentration related to Ig half-life?
Higher concentration, decreased half-life
Which receptors on B cells and macrophages have an immunoregulatory function?
Fc receptors
Co-cross linking of what turns off the effector B cell?
BCR and FcgammaRII
What is Rhogam? When is it administered?
Immune gammaglobulin (IgG Ab) to Rh Ag; given to Rh neg mothers during pregnancy and at parturition
