70 Questions
What is the name of the pathway that regulates T cell deletion by apoptotic cell death?
Mitochondrial pathway
Which protein family is involved in initiating the mitochondrial pathway of T cell deletion?
BCL-2 family proteins
What happens when BAX and BAK insert into the outer mitochondrial membrane during T cell deletion?
Increased mitochondrial permeability
Which event leads to the activation of cytosolic enzymes called caspases during T cell deletion?
Release of cytochrome c from mitochondria
What type of signaling can induce or activate cytoplasmic proteins of the BCL-2 family during T cell deletion?
Receptor-mediated signaling
What is the purpose of peripheral tolerance mechanisms discussed in the text?
To maintain unresponsiveness to self antigens in peripheral tissues
Which cell type is responsible for actively suppressing the activation of lymphocytes specific for self and other antigens in peripheral tolerance?
Regulatory T cells (Tregs)
What is deletion or negative selection in the context of central T cell tolerance?
Death of immature T cells recognizing antigens with high avidity in the thymus
In central T cell tolerance, where does negative selection of thymocytes primarily occur?
Thymic cortex
Which protein plays a crucial role in controlling autoimmune diseases by regulating peripheral tissue antigens in the thymus?
Autoimmune regulator protein (AIRE)
What characterizes autoimmune diseases that are under the control of autoimmune regulator protein (AIRE)?
Damage to multiple endocrine organs and skin
What is the principal function of regulatory T cells?
To suppress immune responses
Which transcription factor is expressed by CD4+ FOXP3+ CD25high T cells?
FOXP3
How are the majority of Tregs in lymphoid tissues derived?
From self antigen expression
What is required for the generation of some Tregs?
TGF-β
What are the two major pathways of apoptosis?
Mitochondrial (intrinsic) pathway and death receptor (extrinsic) pathway
What happens to T lymphocytes that repeatedly stimulated by antigens?
They die by apoptosis
Which pathway involves the activation of cytoplasmic adaptor proteins and procaspase-8?
Extrinsic pathway
Which receptor-ligand pair is most important in inducing apoptosis in T cells?
FAS-FAS ligand (FASL)
Where does central B-cell tolerance mainly occur?
Bone marrow
What is the fate of mature B lymphocytes recognizing self antigens in peripheral tissues without T cell help?
Apoptosis
What mechanism renders some B lymphocytes anergic or leads to their apoptosis when recognizing self antigens?
Signaling by inhibitory receptors - CD22
Which type of T lymphocytes function to control responses to self antigens in peripheral tissues?
T follicular regulatory (Tfr) cells
What happens to some immature T cells in the thymus when they encounter self antigens?
Negative selection (death)
In CD4+ T cells, what induces anergy?
Engagement of inhibitory receptors like CTLA-4 and PD-1
"Receptor editing" may occur in B lymphocytes when:
"Immature B cells recognize multivalent self antigens"
"Peripheral tolerance" in B cells may involve each EXCEPT:
"Proliferation"
What mechanism causes mature CD4+ T cells to become unresponsive to an antigen?
Exposure to the antigen in the absence of costimulation
Which signal is required for full activation of T cells?
Recognition of costimulators by CD28 and recognition of the antigen by the TCR
What occurs in anergic cells that blocks TCR-induced signal transduction?
Blockage of TCR-induced signal transduction
What happens when T cells recognize self antigens in the absence of innate immune responses?
They engage inhibitory receptors of the CD28 family
Which of the following is NOT a mechanism that may function to induce and maintain the anergic state?
Recognition of costimulators by CD28
What is the result of self antigen recognition without costimulation?
Activation of cellular ubiquitin ligases
What initiates the mitochondrial pathway of T cell deletion by apoptotic cell death?
Growth factor deprivation
Which proteins lead to increased mitochondrial permeability during T cell deletion?
BAX and BAK
What factor is crucial for the generation, survival, and functional competence of Regulatory T cells?
TGF-β
What activates cytosolic enzymes called caspases during T cell deletion?
Release of pro-apoptotic mitochondrial proteins into the cytosol
What results from the insertion of BAX and BAK into the outer mitochondrial membrane during T cell deletion?
Leakage of pro-apoptotic mitochondrial proteins
Which pathway of apoptosis is triggered by T lymphocytes recognizing antigens with high affinity or self?
Mitochondrial pathway
What is the primary function of Regulatory T cells?
Suppress immune responses
What type of stimuli can induce or activate cytoplasmic proteins of the BCL-2 family during T cell deletion?
Noxious stimuli
Which transcription factor is expressed by CD4+ FOXP3+ CD25high T cells?
FOXP3
What cytokine is crucial for the survival and functional competence of Regulatory T cells?
IL-2
In which tissues are the majority of Regulatory T cells thought to be derived from?
Thymus
What is the most important death receptor in T cells involved in apoptosis induction?
FAS
Which cell surface receptors are engaged by their ligands in the extrinsic pathway of T cell deletion?
TNF receptor superfamily
What is a homologous ligand to TNF in the context of T cell deletion?
CD95
Which mechanism may render mature B lymphocytes recognizing self antigens in peripheral tissues unresponsive?
CTLA-4 engagement
What is the primary outcome when immature B lymphocytes recognize self antigens with high affinity in the bone marrow?
Receptor editing
What process occurs when T cells encounter self antigens without additional stimuli or repetitive stimulation?
Apoptosis
Which type of tolerance is induced in generative lymphoid organs when immature lymphocytes encounter self antigens?
Central tolerance
What occurs when mature B lymphocytes recognize self antigens in the absence of specific helper T cells?
Apoptotic death
Which event leads to the activation of downstream caspases during apoptosis induction in T cells?
Production of active caspase-8
How are CD4+ T cells rendered anergic in the context of antigen recognition?
Anergy induction
What is the primary effect of anergy on self-reactive T cells?
The cells become unresponsive to the antigen
What is required for full activation of T cells?
Both signal 1 and signal 2
What happens when T cells recognize self antigens in the absence of innate immune responses?
They engage inhibitory receptors of the CD28 family
What is NOT a mechanism that may function to induce and maintain the anergic state?
Anergic cells become hyperresponsive to the antigen
Which cells are primarily responsible for actively suppressing the activation of lymphocytes specific for self and other antigens in peripheral tolerance?
Regulatory T cells
What happens to TCR-associated proteins when self antigen recognition occurs without costimulation?
They are ubiquitinated and targeted for proteolytic degradation
What is the term for the unresponsiveness to an antigen that is induced by exposure to that antigen?
Immunotolerance
What are the antigens that induce tolerance called?
Tolerogens
What is the ability of the immune system to recognize and respond to foreign antigens but not to self antigens called?
Self-non-self discrimination
What is the term for the phenomenon where some developing T and B cells in every individual may express receptors capable of recognizing normal molecules in that individual?
Autoreactivity
What is the term for the process of eliminating and inactivating lymphocytes that express high-affinity receptors for self antigens?
Central tolerance
What is the term for the phenomenon where many self-reactive lymphocytes complete their maturation and are present in healthy individuals?
Imperfect tolerance
What is the term for the process of inducing self-tolerance in immature self-reactive lymphocytes in the generative lymphoid organs?
Central tolerance
What is the term for the process of inducing self-tolerance in lymphocytes in peripheral or mature sites?
Peripheral tolerance
What is the term for the property of the normal immune system that prevents reactions to self antigens?
Self-tolerance
What is the term for the experimental observation that animals that had encountered an antigen under particular conditions would not respond to subsequent exposures to the same antigen?
Immunotolerance
Test your knowledge on the mechanisms of peripheral tolerance in immunotolerance, which are essential for preventing the activation of potentially harmful lymphocytes. Explore how mature lymphocytes in peripheral tissues become unresponsive to self antigens through various mechanisms.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free