Lecture 27 (B cell module)

Question 1

What signals does activation of B cells require

Answer 1

1) Signal 1–> p:BCR
2) Signal 2–> TCR:pMHCII (peptide presented by B cell) (CD40L:CD40)
3) Additional costimulatory signals and cytokines
4) Linked recognition

Question 2

What is Humoral Immunity

Answer 2

When antibodies promote pathogen neutralization, opsonization, and complement activation

Question 3

What induces activated B cells to produce specific types of antibodies?

Answer 3

Secreting IL-21 and either Type 1 (INFgamma), Type 2 (IL-4), or Type 3 (IL-17) cytokines

Question 4

What cells directly interact with B cells

Answer 4

TFH cells

Question 5

What antibody class serves as a receptor on Naive B cells

Answer 5

IgM

Question 6

Where do B cells arise

Answer 6

Bone marrow

Question 7

Main characteristics of B cells (innate immunity)

Answer 7

1) Antigen specific
2) Clonotypic
3) Progenitors of antibody producing plasma cells and plasmablasts

Question 8

BCR is?

Answer 8

Membrane bound

Question 9

Action once B cell is activated

Answer 9

Secretes BCR (antibody)

Question 10

Overall process of clonal selection

Answer 10

Activated B cells undergo proliferation and differentiation–>plasma cell that secretes antibodies (outcome)

Question 11

Where do B cells circulate?

Answer 11

In periphery and through lymph nodes and spleen

Question 12

Entry and exit of B cells through the lymph node

Answer 12

Entry–>High Endothelial Venules (HEV)
Exit–>Efferent Lymphatics

Question 13

Outcome of B cell encountering or NOT encountering Antigen

Answer 13

B cell + no antigen–>dies of apoptosis after a few months
B cell + antigen–>provides survival signal (signal 1)

Question 14

How do antigen end up in lymph node

Answer 14

1) Antigens from pathogens via afferent lymphatics
2) Antigens opsonized by complement pathway
3) Antigens transported by activated conventional Dendritic cells (antigen then transferred to follicular DC in lymph node)

Question 15

What retains antigen in lymph node

Answer 15

Subscapular sinus macrophage (SCS macrophage)

Question 16

Mechanism of how antigen is retained in lymph node

Answer 16

Subscapular sinus macrophage (SCS macrophage) express complement receptor on surface–> complement receptor binds to complement on opsonized antigen–>antigen retained in lymph node

Question 17

SCS macrophage trait

Answer 17

Low endocytic and low degradative activity

Question 18

What co receptor does B cell express

Answer 18

Complement receptors CD19 and CD21 (binds complement to enhance signaling and activation)

Question 19

Main outcomes of BCR:AG signaling

Answer 19

1) Transcription factors are activated leading to gene transcription
2) Survival signal (signal 1)
3) Cytoskeletal reorganization

Question 20

Pathway used to process antigen and the MHC class in B cells

Answer 20

Exogenous pathway and MHC class II

Question 21

What provides Signal 2

Answer 21

Activated CD4+ TFH Cell and TLR signaling

Question 22

Specific binding that induces Signal 2

Answer 22

1) pMHC binding to TCR and co-receptor on TFH cell
2) CD40 on B cells binding to CD40L on TFH cells

Question 23

Difference between recognition of Antigen by B cells vs T cells

Answer 23

B cells: recognize antigen in natural form
T cells: recognize antigen presented on MHC on the surface of APCs