Humoral Immunity: Antigen Recognition (Detection)

Question 1

clonal expansion

Answer 1

activation and proliferation of b cells with receptors specific to the pathogenic agent

Question 2

plasma cells

Answer 2

mature B-lymphocytes that reside in bone marrow but secrete antibodies into plasma specific for antigen

Question 3

heavy-chain isotype switching

Answer 3

expression of heavy chains appropriate for an infectious agent due to cytokines from Helper T cells

Question 4

affinity maturation

Answer 4

the process of generating antibodies with increasingly high affinity after repeated bouts of infection or immunization. The genetic mechanism is somatic hypermutation

Question 5

T-dependent Humoral Response

Answer 5

response of B cells to proteins depends on stimulation from Helper T Cells

Question 6

T independent Humoral Response

Answer 6

response to polysaccharides and lipids

Question 7

follicular B cells

Answer 7

reside in the follicles of lymphoid organs, T-dependent, class switched, and high affinity antibody maturation

Question 8

Marginal-zone B cells

Answer 8

location: peripheral regions of splenic white pulp respond to blood-borne polysaccharide antigens
mostly IgM response

Question 9

B-1 cells

Answer 9

respond to nonprotein antigens in mucosal tissues and peritoneum
mostly IgM response

Question 10

primary response

Answer 10

usually lasts 5-10 days
IgM> IgG
lower affinity

Question 11

secondary response

Answer 11

usually lasts 1-3 days
isotype switching, generally favors IgG
higher average affinity

Question 12

Ig alpha and beta

Answer 12

proteins associated with membrane IgM and IgD receptors, help form the BCR copmlex
ITAMs in their cytoplasmic domain promote signal transduction after phosphorylation by Fyn, Lyn, and Blk

Question 13

Syk

Answer 13

a tyrosine kinase analog of ZAP-70 that binds to phosphorylated ITAMs activate adaptor proteins

Question 14

cross-linking

Answer 14

a key feature of B cell activation, when a single repeating antigen or multiple antigens bind one or more membrane receptor proteins

Question 15

C3d-CR2

Answer 15

C3d complement coats pathogens. CR2 receptor expressed on B-cells binds C3d and strongly promotes signlaing

Question 16

TLR

Answer 16

toll-like receptors, innate immune receptors expressed on a number of cells, including B cells, that promote immune reaction

Question 17

Tfh

Answer 17

follicular Helper T cells
f(x): trigger formation of a germinal center
Helper T cells stimulated by B-cell antigen presentation mature in Tfh in lymph nodes.

Question 18

germinal center reaction

Answer 18

B cell maturation in lymph nodes that involves isotype switching, somatic hypermutation, and production of memory cells

Question 19

interfollicular regions

Answer 19

the region of lymph organs where B and T cells mix due to CCR7/ CXCR5 signaling

Question 20

CCR7

Answer 20

a receptor that promotes migration toward T-cell rich regions

Question 21

CXCR5

Answer 21

a receptor which promotes migration into B cell follicles

Question 22

T-dependent B cells response: bidirectional interaction

Answer 22

1. T and B cells are activated in different regions of the same lymphoid organ
2. Chemokines signaling causes them to meet
   i. chemokines induce B cells to express CXCR5 which promotes migration toward T cells
   ii. chemokines induced T cells to produce CCR7 which promote migration toward B cells
3. B cell antigen presentation- b cells ingest protein antigens, present multiple fragment to T cells
4. Key Event: Germinal Cell production
   i. activated Helper T Cells express CD40L
   ii. CD40L binds to CD40 on B lympohcytes
   iii. signaling stimulates migration into nodes and activates germinal center reactions

Question 23

ICOS

Answer 23

inducible costimulator, important for commitment of helper T cels to follicular helper cells