Antigen-receptors, MHC, and antigen-presentation

Question 1

What are antigen-receptors?

Answer 1

Specialized receptors on B and T cells that recognize specific antigens, triggering immune responses.

Question 2

What is MHC (Major Histocompatibility Complex)?

Answer 2

Molecules on the surface of cells that present antigens to T cells, aiding in the recognition of pathogens or infected cells.

Question 3

What does MHC Class I do?

Answer 3

Presents endogenous antigens (e.g., from viruses) to CD8+ cytotoxic T cells.

Question 4

What does MHC Class II do?

Answer 4

Presents exogenous antigens (e.g., from bacteria) to CD4+ helper T cells.

Question 5

What is antigen presentation?

Answer 5

The process by which cells display antigen fragments on their MHC molecules to activate T cells.

Question 6

What is a BCR (B-cell receptor)?

Answer 6

A membrane-bound antibody on B cells that binds to specific antigens, initiating an immune response.

Question 7

What is a TCR (T-cell receptor)?

Answer 7

A receptor on T cells that recognizes processed antigens presented by MHC molecules on the surface of other cells.

Question 8

What is cross-presentation?

Answer 8

The process where dendritic cells present exogenous antigens on MHC Class I molecules to activate CD8+ T cells.

Question 9

What are endogenous antigens?

Answer 9

Antigens originating from inside the cell, such as viral proteins, presented on MHC Class I molecules.

Question 10

What are exogenous antigens?

Answer 10

Antigens from outside the cell, such as bacterial proteins, presented on MHC Class II molecules.

Question 11

What is antigen-processing?

Answer 11

The breakdown of proteins into smaller peptides for presentation on MHC molecules.

Question 12

What are CD8+ T cells?

Answer 12

Cytotoxic T cells that recognize antigens presented by MHC Class I molecules and kill infected cells.

Question 13

What are CD4+ T cells?

Answer 13

Helper T cells that recognize antigens presented by MHC Class II molecules and assist other immune cells in responding.

Question 14

What are APCs (Antigen-presenting cells)?

Answer 14

Cells like dendritic cells, macrophages, and B cells that present antigens to T cells.

Question 15

What are dendritic cells?

Answer 15

The most potent APCs, crucial for initiating immune responses by presenting antigens to T cells.

Question 16

What are cytotoxic T cells (CD8+)?

Answer 16

T cells that kill infected or cancerous cells upon recognition of antigens on MHC Class I molecules.

Question 17

What are helper T cells (CD4+)?

Answer 17

T cells that activate other immune cells, such as B cells and cytotoxic T cells, in response to antigens presented on MHC Class II.

Question 18

What is a peptide-MHC complex?

Answer 18

The combination of an antigenic peptide and an MHC molecule that is recognized by T-cell receptors.

Question 19

What is clonal selection?

Answer 19

The process by which a specific T or B cell is selected for activation and proliferation upon recognition of its specific antigen.

Question 20

What is an immune synapse?

Answer 20

The interface between an antigen-presenting cell and a T cell, where antigen recognition and signal transduction occur.

Question 21

What is T-cell activation?

Answer 21

The process by which T cells become activated upon binding to antigen-MHC complexes on APCs.

Question 22

What is B-cell activation?

Answer 22

The process by which B cells become activated after binding an antigen with their BCR, leading to antibody production.

Question 23

What is MHC polymorphism?

Answer 23

The genetic diversity in MHC molecules that allows the immune system to recognize a wide variety of antigens.

Question 24

What is antigenic variation?

Answer 24

The ability of pathogens to alter their surface antigens to evade immune recognition.

Question 25

What is self-tolerance?

Answer 25

The ability of the immune system to recognize and ignore the body’s own cells to prevent autoimmunity.

Question 26

What are superantigens?

Answer 26

Pathogen-derived proteins that can activate a large number of T cells by binding to the MHC Class II molecules and TCRs, leading to excessive immune activation.