Lecture 3.2 - Adaptive Immunity

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Questions and Answers

What is the primary function of MHC I in the immune response?

To activate B cells

To present antigens to CD4+ T cells

To present antigens to CD8+ T cells (correct)

To recognize and remove apoptotic cells

What is the outcome of T cell tolerance?

Proliferation of cytotoxic T cells

Enhanced inflammatory response

Prevention of autoimmune responses (correct)

Activation of B cells

Which type of T cell is involved in the activation of B cells?

Regulatory T cells

Cytotoxic T cells

Memory T cells

Helper T cells (correct)

What is the primary function of antigen presenting cells?

To process and present antigens to T cells Signup and view all the answers

What is the outcome of V(D)J recombination?

Production of a vast range of unique receptors Signup and view all the answers

What is the role of CD4 in the immune response?

To interact with MHC II and activate helper T cells Signup and view all the answers

What is the difference between MHC I and MHC II?

MHC I presents endogenous antigens, while MHC II presents exogenous antigens Signup and view all the answers

What is the role of T cell receptors in the immune response?

To recognize and respond to a specific antigen Signup and view all the answers

What is the primary role of the B cell receptor?

To internalize and process antigens Signup and view all the answers

What is the primary function of opsonins?

To label pathogens for clearance by phagocytes Signup and view all the answers

What is the outcome when a primed T cell encounters a B cell displaying the same antigen?

The B cell is activated and proliferates Signup and view all the answers

What is the primary mechanism of antigen presentation by B cells?

Antigen presentation through MHC II Signup and view all the answers

What is the role of Fc receptors on phagocytes?

To internalize opsonized pathogens Signup and view all the answers

What is the outcome when IgG binds to its antigen?

The complement pathway is activated Signup and view all the answers

What is the primary mechanism of pathogen clearance by phagocytes?

Internalization of opsonized pathogens Signup and view all the answers

What is the role of IL-2 in B cell activation?

It causes the expansion of T cells that recognize the antigen Signup and view all the answers

What is the primary function of dendritic cells in the process of adaptive immunity?

To phagocytose invading microorganisms and present antigens to T cells Signup and view all the answers

Which type of T cell is responsible for producing cytokines that cause proliferation of cytotoxic T cells?

CD4+ helper T cells Signup and view all the answers

What is the primary mechanism by which the immune system determines whether a cell is 'self' or 'non-self'?

Through the recognition of antigens presented on MHC I and II molecules Signup and view all the answers

What is the fate of T cells that recognize 'self' antigens during their development in the thymus?

They are directed towards apoptosis Signup and view all the answers

What is the primary function of B cells in the process of adaptive immunity?

To produce antibodies against specific antigens Signup and view all the answers

What type of T cell is responsible for recognizing antigens presented on MHC I molecules and killing virus-infected cells directly?

CD8+ cytotoxic T cells Signup and view all the answers

What is the primary role of MHC II molecules in the process of adaptive immunity?

To present antigens to CD4+ helper T cells Signup and view all the answers

What is the fate of B cells that recognize specific antigens during the process of adaptive immunity?

They mature into plasma cells and produce antibodies Signup and view all the answers

Study Notes

T Cell Tolerance and Antigen Presentation

MHC I interacts with CD8 on cytotoxic T cells, essential for cancer cell detection and clearance, as well as virally infected cells.
MHC II interacts with CD4 on helper T cells, displaying antigens processed by antigen presenting cells, leading to adaptive immune response.

Antigen Presentation

Antigen presentation is a two-step process occurring in lymph nodes, with antigen presenting cells presenting antigens to T cells.
T cell receptors are specific to a single antigen, and B cells only produce specific antibodies to specific antigens.

Antigen Processing Pathways

V(D)J recombination is a process of gene rearrangement, producing a vast range of unique receptors.

T Cell/B Cell Interaction

T cells must "help" B cells to effectively respond to antigens, with B cells having receptors specific to a single antigen.

Adaptive Immunity

Adaptive immunity is the process of eliciting a specific immune response, with T cells and B cells residing in peripheral lymphoid tissue.
Each T cell has a T cell receptor specific to a single antigen, and each B cell has a B cell receptor specific to a single antigen.

Cells of the Immune System

Dendritic cells phagocytose invading microorganisms, exhibiting antigen on MHC II molecules, and travel to lymph nodes to interact with T cells.
T cells proliferate into CD4+ Helper T cells, interacting with B cells, which then mature into plasma cells producing antibodies.

T Cells

T cells mature in the Thymus, originate from haematopoietic stem cells, and are screened for self-antigen recognition, with those that do undergoing apoptosis.

Major Histocompatibility Complex (MHC)

MHC proteins exist on the surface of cells, displaying proteins made within the cell, allowing the immune system to determine self or non-self.

B Cells

B cell receptors are essentially immunoglobulins, with B cells internalizing antigens and presenting them on MHC II.

Immunoglobulins

Immunoglobulins are proteins produced by B cells, having an affinity for a unique antigen.

Opsonisation

Opsonisation is the process of labelling pathogens for clearance by phagocytes, with opsonins being molecules that attach to antigens on the surface of pathogens.

IgG and Complement

IgG can activate the complement pathway once bound to its antigen, with classical, alternative, and lectin pathways.

Clearance of Opsonised Pathogen

Complement can "punch holes" in the cell membrane of the pathogen, leading to death, and phagocytes internalize the pathogen, producing reactive oxygen species to destroy it.

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Description

Learn about the role of MHC I and II in T cell interactions, antigen presentation, and immune tolerance. Understand how MHC molecules interact with CD4 and CD8 on T cells to trigger immune responses.