Antibody and Cell-Mediated Effector Functions

Question 1

What are the antibody-mediated effector functions?

Answer 1

Antibodies neutralize pathogens, opsonize them for phagocytosis, and activate the complement system.

Question 2

What is neutralization by antibodies?

Answer 2

Antibodies bind to pathogens or toxins, blocking their ability to infect cells or cause damage.

Question 3

What is opsonization?

Answer 3

Antibodies coat pathogens, making them easier for phagocytes to recognize and engulf.

Question 4

How do antibodies activate the complement system?

Answer 4

Antibodies (mainly IgM and IgG) bind to antigens, activating the complement cascade, leading to pathogen lysis.

Question 5

What is antibody-dependent cell-mediated cytotoxicity (ADCC)?

Answer 5

Antibodies bound to target cells recruit NK cells, which kill the antibody-coated cells.

Question 6

What are Fc receptors?

Answer 6

Receptors on immune cells (e.g., macrophages, neutrophils, NK cells) that bind the Fc region of antibodies, triggering effector functions like phagocytosis and cytotoxicity.

Question 7

What are IgM antibodies?

Answer 7

The first antibodies produced during an immune response, effective at activating complement and neutralizing pathogens.

Question 8

What are IgG antibodies?

Answer 8

Provide long-term immunity, are involved in neutralization, opsonization, and complement activation.

Question 9

What are IgA antibodies?

Answer 9

Found in mucosal areas, they protect against pathogens at mucosal surfaces by preventing their attachment.

Question 10

What are IgE antibodies?

Answer 10

Involved in allergic responses and defense against parasitic infections by binding to allergens and activating mast cells.

Question 11

What is cell-mediated immunity?

Answer 11

Involves T cells that directly kill infected cells or help other immune cells to respond to pathogens.

Question 12

What are cytotoxic T cells (CD8+ T cells)?

Answer 12

Kill infected or cancerous cells by recognizing antigens presented on MHC Class I molecules.

Question 13

What are helper T cells (CD4+ T cells)?

Answer 13

Activate other immune cells, such as cytotoxic T cells, macrophages, and B cells, by releasing cytokines.

Question 14

What is a T-cell receptor (TCR)?

Answer 14

On T cells, recognizes processed antigens presented on MHC molecules, triggering immune responses.

Question 15

What are MHC Class I molecules?

Answer 15

Present endogenous antigens to CD8+ T cells, which kill infected cells.

Question 16

What are MHC Class II molecules?

Answer 16

Present exogenous antigens to CD4+ T cells, which help activate other immune cells.

Question 17

What is T-cell activation?

Answer 17

Occurs when a TCR binds to an antigen-MHC complex, with co-stimulatory signals needed for full activation.

Question 18

What is clonal expansion of T cells?

Answer 18

Activated T cells proliferate, producing effector T cells that combat the antigen and memory T cells for faster future responses.

Question 19

What is T-cell memory?

Answer 19

Memory T cells persist long-term and provide rapid responses upon re-exposure to the same antigen.

Question 20

What are cytotoxic T cell effector functions?

Answer 20

Release perforin and granzymes to induce apoptosis in infected or cancerous cells.

Question 21

What is perforin?

Answer 21

A protein released by cytotoxic T cells that forms pores in target cell membranes, allowing granzymes to enter.

Question 22

What are granzymes?

Answer 22

Enzymes released by cytotoxic T cells that trigger apoptosis in target cells.

Question 23

What is the Fas-FasL interaction?

Answer 23

FasL on cytotoxic T cells binds to Fas on target cells, triggering apoptosis via the extrinsic pathway.

Question 24

What are T helper 1 (Th1) cells?

Answer 24

Activate macrophages and cytotoxic T cells to fight intracellular pathogens like viruses and bacteria.

Question 25

What are T helper 2 (Th2) cells?

Answer 25

Stimulate B cells to produce antibodies, especially effective against extracellular pathogens.

Question 26

What are T helper 17 (Th17) cells?

Answer 26

Promote inflammation and recruit neutrophils to fight fungal infections and some bacterial infections.

Question 27

What are T follicular helper (Tfh) cells?

Answer 27

Assist B cells in germinal centers to produce high-affinity antibodies and form memory B cells.

Question 28

What are regulatory T cells (Tregs)?

Answer 28

Suppress immune responses to maintain self-tolerance and prevent autoimmune reactions.

Question 29

What is the role of macrophages in cell-mediated immunity?

Answer 29

Activated by Th1 cells, macrophages increase phagocytosis and pathogen destruction.

Question 30

What are granulocytes in immunity?

Answer 30

Neutrophils, eosinophils, and basophils contribute to defense through phagocytosis, degranulation, and inflammation.

Question 31

What is the role of NK cells in immunity?

Answer 31

Natural killer cells recognize and kill cells infected with viruses or transformed by cancer, even without antigen-specific receptors.

Question 32

What is an immune synapse?

Answer 32

The contact site between a T cell and its target cell, where antigen recognition and signaling take place.

Question 33

What are lymphokine-activated killer (LAK) cells?

Answer 33

NK cells or cytotoxic T cells activated by cytokines to enhance their killing ability.

Question 34

What is antibody isotype switching?

Answer 34

B cells can switch from producing IgM to IgG, IgA, or IgE in response to different pathogens or cytokine signals.

Question 35

What is humoral immunity?

Answer 35

Mediated by antibodies produced by plasma cells, it targets extracellular pathogens and toxins.

Question 36

What is immunotherapy targeting T cells?

Answer 36

Includes strategies like checkpoint inhibitors or CAR-T cell therapy to enhance T-cell responses against tumors.

Question 37

What is tumor immunity?

Answer 37

Cytotoxic T cells and NK cells recognize and kill tumor cells displaying abnormal antigens on MHC molecules.

Question 38

How do pathogens evade the immune system?

Answer 38

Pathogens can evade immune detection by altering their antigenic profile or inhibiting T-cell activation.