MICR223_L16_immunology introduction

What is the difference between innate and adaptive immunity?

Innate immunity is the immediate, non-specific defense system (e.g., physical barriers, immune cells like NK cells), while adaptive immunity involves specific responses from B and T cells.

What are Pattern Recognition Receptors (PRRs)?

PRRs are proteins on immune cells that recognize Pathogen-Associated Molecular Patterns (PAMPs) and Damage-Associated Molecular Patterns (DAMPs).

What do Toll-like receptors (TLRs) recognize?

TLRs recognize various PAMPs such as lipopolysaccharide (LPS), flagellin, and viral RNA.

What do PRRs activate in cells?

PRRs activate antigen presenting cells like dendritic cells (DC), enhancing their ability to stimulate T cells.

What is the role of CD4 and CD8 molecules in T cell activation?

CD4 molecules assist in binding TCR to MHC-II, while CD8 molecules stabilize TCR binding to MHC-I for T cell activation.

What triggers 'Signal 1' in T cell activation?

Signal 1 is triggered by antigen/MHC binding to the TCR, initiated by serial triggering of MHC-TCR interactions.

What is the purpose of costimulation in T cell activation?

Costimulation provides a secondary signal needed alongside TCR signaling for full T cell activation.

What is the role of dendritic cells in activating T helper cells?

Dendritic cells phagocytose pathogens and provide costimulatory signals to T helper cells through MHC-II interactions.

How do T helper cells assist B cells?

T helper cells release cytokines that stimulate B cells to produce antibodies.

What is the significance of 'missing self' in NK cell activation?

NK cells are activated by detecting low or absent MHC-I expression on target cells, leading to the killing of those cells.

What role do regulatory T cells (Tregs) play in immune tolerance?

Tregs help maintain peripheral tolerance by secreting immunosuppressive cytokines and preventing activation of autoreactive T cells.

Describe central tolerance in T cells.

Central tolerance involves the deletion of autoreactive T cells in the thymus and the selection of T cells that react moderately to self-antigens.

What are the mechanisms of peripheral tolerance?

Peripheral tolerance can occur when T cells are activated without costimulation, leading to anergy or functional inactivation.

What is the effect of costimulation absence on T cells?

T cells may become anergic, meaning they lose their ability to respond to antigens in the absence of costimulation.

What are the components of the adaptive immune system?

The adaptive immune system primarily consists of B cells and T cells that provide specific immunity.

What does MHC-I present to T cells?

MHC-I presents peptides from intracellular pathogens to CD8 cytotoxic T cells.

What happens when TCR binds a strong signal in thymus?

T cells that bind with a strong signal to self-antigens are deleted through negative selection.

What cytokines do T helper cells produce?

T helper cells produce cytokines such as IL-2 and help stimulate B cells and cytotoxic T cells.

What is the function of perforin in cytotoxic T cells?

Perforin forms pores in the target cell membrane, allowing granzymes to enter and induce apoptosis.

What immune response do babies have at birth?

Neonatal tolerance mechanisms are in place; infants are often immunocompromised and may exhibit tolerance to self-antigens.

What is the role of dendritic cells in providing full T cell activation?

Dendritic cells must not only present antigen but also provide costimulation to achieve complete T cell activation.

What leads to the killing of cancer or virally infected cells?

Cytotoxic T cells recognize and kill infected or cancerous cells based on MHC-I presenting viral peptides.

When are Tregs produced, and what do they help with?

Tregs are produced early in life to help maintain tolerance and prevent autoimmune reactions.

What happens to autoreactive B cells during development?

Autoreactive B cells that recognize self-antigens undergo programmed cell death in the bone marrow.

What defines the role of NK cells in the immune response?

NK cells play a crucial role in innate immunity by detecting and killing cells with altered MHC-I expression.

How do the innate and adaptive immune systems interact?

The innate immune system activates antigen-presenting cells that subsequently boost the adaptive immune response.

What are the 'danger signals' that help activate dendritic cells?

'Danger signals' come from pathogens and activate dendritic cells via PRR signaling, enhancing T cell response.

Explain the principle of serial triggering in T cell activation.

Serial triggering allows one MHC molecule to activate multiple TCRs, thus increasing the efficiency of antigen recognition.