B cells: Development, activation and humoral immunity

Question 1

B-cell development:

Answer 1

B cells develop in the bone marrow, where they undergo selection processes to ensure self-tolerance.

Question 2

Bone marrow selection:

Answer 2

B cells that bind self-antigens with high affinity are eliminated to prevent autoimmunity.

Question 3

B-cell receptor (BCR):

Answer 3

A membrane-bound antibody that allows B cells to recognize specific antigens.

Question 4

Naïve B cells:

Answer 4

Mature B cells that have not yet encountered their specific antigen.

Question 5

B-cell activation:

Answer 5

Occurs when the BCR binds to its specific antigen, and co-stimulatory signals from helper T cells are provided.

Question 6

Helper T-cell support for B cells:

Answer 6

Activated CD4+ T cells provide cytokines and co-stimulatory signals that help B cells proliferate and differentiate.

Question 7

Clonal expansion of B cells:

Answer 7

Activated B cells proliferate, creating a population of identical cells to combat the antigen.

Question 8

B-cell differentiation:

Answer 8

Activated B cells differentiate into plasma cells (antibody-secreting cells) and memory B cells.

Question 9

Plasma cells:

Answer 9

Differentiated B cells that secrete large amounts of antibodies specific to the antigen.

Question 10

Antibody production:

Answer 10

Plasma cells produce antibodies (immunoglobulins) that bind to antigens, neutralize them, or mark them for destruction.

Question 11

Humoral immunity:

Answer 11

The immune response mediated by antibodies produced by B cells, targeting pathogens and toxins.

Question 12

Isotype switching:

Answer 12

B cells can change the class of antibody they produce (e.g., from IgM to IgG) in response to cytokine signals.

Question 13

Memory B cells:

Answer 13

Long-lived B cells that remain after infection resolution, providing rapid antibody production upon re-exposure to the same antigen.

Question 14

Antigen presentation by B cells:

Answer 14

B cells can act as antigen-presenting cells (APCs), presenting processed antigen to helper T cells to enhance activation.

Question 15

T-independent activation:

Answer 15

Some antigens, like polysaccharides, can activate B cells without T cell help, though this response is weaker and lacks memory.

Question 16

T-dependent activation:

Answer 16

Requires help from CD4+ T cells for full activation, leading to stronger antibody responses and memory formation.

Question 17

IgM antibodies:

Answer 17

The first antibodies produced during an immune response, primarily produced by activated B cells.

Question 18

IgG antibodies:

Answer 18

Antibodies produced after isotype switching, important for long-term immunity and pathogen neutralization.

Question 19

IgA antibodies:

Answer 19

Found in mucosal areas, providing protection against pathogens entering through mucosal surfaces.

Question 20

IgE antibodies:

Answer 20

Involved in allergic reactions and defense against parasitic infections.

Question 21

Antibody affinity maturation:

Answer 21

During immune responses, B cells undergo mutations in their antibody genes, leading to higher-affinity antibodies.

Question 22

Somatic hypermutation:

Answer 22

A process where mutations occur in the variable regions of the BCR genes, allowing B cells to produce antibodies with increased affinity for the antigen.

Question 23

Follicular B cells:

Answer 23

B cells that reside in lymphoid follicles and are crucial for generating memory B cells and high-affinity antibodies.

Question 24

Marginal zone B cells:

Answer 24

B cells found in the spleen that respond to blood-borne antigens and are involved in T-independent responses.

Question 25

B-cell tolerance:

Answer 25

The process by which B cells are prevented from reacting against self-antigens, ensuring self-tolerance.

Question 26

B-cell activation in secondary lymphoid organs:

Answer 26

Activated B cells undergo clonal expansion and differentiation in lymph nodes and spleen after encountering antigen.

Question 27

Antibody-mediated immunity:

Answer 27

Antibodies bind to pathogens or toxins, neutralizing them or marking them for phagocytosis or complement activation.

Question 28

Complement activation by antibodies:

Answer 28

Antibodies, particularly IgM and IgG, can activate the complement system, leading to pathogen destruction.

Question 29

Opsonization:

Answer 29

Antibodies enhance phagocytosis by marking pathogens for recognition and engulfment by phagocytes.

Question 30

Antibody-dependent cell-mediated cytotoxicity (ADCC):

Answer 30

Antibodies bound to target cells can recruit NK cells to destroy infected or tumor cells.

Question 31

B-cell memory response:

Answer 31

Upon re-exposure to an antigen, memory B cells rapidly differentiate into plasma cells and secrete antibodies.

Question 32

Humoral immunity and vaccines:

Answer 32

Vaccines stimulate the production of memory B cells and antibodies to provide long-term immunity against pathogens.