NF-AT Pathway and T Cell Activation

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Questions and Answers

What type of interaction during thymic selection is positively selected in T cells?

Weak interaction with MHC and peptide

Intermediate interaction with MHC and peptide (correct)

No interaction with MHC

Strong interaction with MHC and peptide

Which mechanism of graft rejection involves TCR recognizing foreign MHC regardless of peptide?

Indirect rejection

Humoral rejection

Direct rejection (correct)

Cell-mediated rejection

What is the primary purpose of HLA typing in transplantation?

To evaluate innate immune responses

To identify infectious agents

To assess graft rejection mechanisms

To match class I and class II MHC genes for compatibility (correct)

What describes a characteristic of the innate immune system?

Provides a quick response within minutes to hours Signup and view all the answers

Which process marks the first encounter of pathogens by the immune system?

Breach of epithelial barriers Signup and view all the answers

What is the role of pattern recognition receptors (PRRs)?

To bind pathogen-associated molecular patterns (PAMPs) Signup and view all the answers

What distinguishes neutrophils from macrophages in terms of their behavior during an infection?

Neutrophils migrate from the blood to tissues during infection Signup and view all the answers

How do macrophages utilize respiratory burst in their defense mechanism?

To generate reactive oxygen species to kill pathogens Signup and view all the answers

What is the primary function of defensins?

To kill bacteria through antimicrobial properties Signup and view all the answers

Where do macrophages and dendritic cells originate before maturing and migrating?

The bone marrow Signup and view all the answers

What role does calcium play in the NF-AT pathway?

Combines with calmodulin to activate calcineurin. Signup and view all the answers

Which molecule is necessary for full T cell activation?

CD28 binding to B7 on APC. Signup and view all the answers

What effect does CTLA4 have in T cell regulation?

Blocks B7 from binding CD28. Signup and view all the answers

What is the significance of LFA-1 binding to ICAM-1?

Facilitates stable interaction between T cells and APCs. Signup and view all the answers

Which statement about TCR and BCR is correct?

BCR is bivalent while TCR is monovalent. Signup and view all the answers

What is the function of the CD4 molecule?

It provides a coreceptor role for T cell activation. Signup and view all the answers

Which statement describes clonality in adaptive immunity?

Each cell expresses a receptor with unique specificity. Signup and view all the answers

What is the purpose of peripheral tolerance?

To maintain homeostasis and prevent autoimmunity. Signup and view all the answers

Which cytokine is NOT secreted by macrophages and dendritic cells?

IL-10 Signup and view all the answers

What triggers the classical pathway of the complement system?

Antibody/antigen complex Signup and view all the answers

What is the primary function of C3b in the complement system?

Opsonization Signup and view all the answers

Which receptor is recognized for directly facilitating phagocytosis?

Macrophage mannose receptor (MMR) Signup and view all the answers

What characteristic is true about neutrophils?

They consume pathogens quickly and die shortly after. Signup and view all the answers

What is the role of mannose binding lectin (MBL) in the immune response?

Facilitates opsonization and complement initiation. Signup and view all the answers

Which type of receptors recognizes bacterial polypeptides but is NOT involved in phagocytosis?

fMLP receptors Signup and view all the answers

What role does C3a play in the complement system?

Induction of inflammation Signup and view all the answers

What is the role of Toll-like receptors (TLRs) in the immune response?

They engage in signaling pathways that trigger a specific cellular response. Signup and view all the answers

Which TLR is specifically involved in the recognition of double-stranded RNA viruses?

TLR3 Signup and view all the answers

What major immune cells are involved in the response mediated by TLRs?

Macrophages and dendritic cells Signup and view all the answers

Which combination of proteins is recognized by TLR4 during the immune response?

LPS, MD-2, and CD14 Signup and view all the answers

Which of the following is true regarding innate and adaptive immune mechanisms?

Adaptive mechanisms build upon the innate response. Signup and view all the answers

What is the primary function of complement proteins in the immune system?

To enhance phagocytosis and inflammation. Signup and view all the answers

Which cytokine signaling pathway is typically associated with TLR signal transduction?

MyD88 pathway Signup and view all the answers

What characterizes the classes of pathogens recognized by immune mechanisms?

Pathogens are identified based on their specific traits. Signup and view all the answers

Which immune cells differentiate in the thymus?

T cells Signup and view all the answers

In terms of pathogen recognition, what do mannose-binding lectins primarily identify?

Microbial carbohydrates Signup and view all the answers

Study Notes

NF-AT Pathway

IP3 facilitates intracellular calcium release from storage.
Calcium binds to calmodulin, activating calcineurin.
Dephosphorylation of NFAT occurs, allowing it to enter the nucleus for gene transcription, e.g., IL-2 production.
Inhibiting this pathway can reduce NFAT activation by preventing dephosphorylation.
Similar signaling pathways exist in B cells, maintaining activation via PLCgamma2.

Secondary Signals in T Cell Activation

CD4 and CD8 T cells require secondary signals for activation.
CD28 binds to B7 on antigen-presenting cells (APCs) for full T cell activation.
If T cells recognize antigen without co-stimulation, they may enter a state of anergy.
CD28 modulates signaling pathways including NFAT, NF-kB, and AP-1.

CTLA-4 and T Cell Regulation

CTLA-4 is homologous to CD28 but has a stronger affinity for B7.
CTLA-4-Ig is a drug that blocks B7, inhibiting T cell activation.
CTLA-4 is crucial for maintaining T cell homeostasis.

T Cell and APC Interactions

Costimulatory signals and adhesion responses facilitate T cell interactions.
LFA-1 binding to ICAM-1 enhances stability of T cell-APC contact.
Initial binding between TCR and APC increases affinity of LFA-1/ICAM-1 interaction.

B Cell Development and Antibody Generation

BCR/Ig functions in diverse immune roles, establishing central and peripheral tolerance.
Adaptive immunity hallmarks: clonality, specificity, diversity, and repertoire.
TCR is monovalent while BCR is bivalent, aiding in immune response diversity.
Thymic selection processes ensure T cells interact appropriately with MHC molecules.

MHC and Transplantation

Graft rejection mechanisms: direct (TCR recognizes foreign MHC) and indirect (APCs present foreign MHC on recipient's MHC).
HLA typing ensures compatibility during transplantation with vast combinations of MHC molecules.

Immune Evasion Mechanisms

Pathogens can evade immune detection by inhibiting the loading or expression of MHC molecules.

Innate Immunity Overview

Innate immune response is rapid (minutes/hours) and recognizes patterns associated with pathogens.
Characteristic features include germ line-encoded receptors and strong self/nonself discrimination.
Complement proteins and interferons are key components of innate immunity.

Pathogen Recognition

PAMPs (Pathogen-Associated Molecular Patterns) are recognized by PRRs (Pattern Recognition Receptors) throughout the immune system.
Major cells with PRRs include neutrophils, dendritic cells, and macrophages.

Cellular Responses of Innate Immunity

Macrophages and dendritic cells arise from monocytes and infiltrate tissues.
Neutrophils are present in blood but migrate to tissues during infections; they have a short lifespan.

Macrophage Functionality

Phagocytosis involves engulfing pathogens and destroying them with lysosomal enzymes.
Respiratory burst increases oxygen use, generating toxic forms of oxygen to kill pathogens.
Cytokines produced by macrophages include IL-1, IL-6, IL-8, IL-12, and TNF-α.

Complement System

Classical pathway is triggered by antibody-antigen complexes; the alternative pathway responds to microbial cell walls.
Both pathways convert C3 into C3b and C5b, which facilitate opsonization and membrane pore formation leading to pathogen lysis.

Toll-Like Receptors (TLRs)

TLRs detect specific microbial components, triggering immune responses tailored to the pathogen type.
Engagement of TLRs activates various transcription factors that modulate cytokine production, enhancing immune responses against pathogens.

Adaptive Immunity Basics

Adaptive immune response is characterized by clonal selection and the differentiation of CD4 cells according to infection type.
B cells undergo maturation in the bone marrow, while T cells develop in the thymus, essential for effective immune responses.

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Description

Explore the intricate NF-AT pathway involved in T cell activation, including the roles of calcium signaling, secondary signals, and the regulation of T cells by CTLA-4. This quiz covers crucial aspects of immunology related to T cell function and co-stimulation. Test your knowledge on how these mechanisms impact immune response.