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Regulation of immune response immunotolerance

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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.

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