B Cells and Humoral Immunity

Question 1

Characteristics of B lymphocytes

Answer 1

responsible for humoral immunity
develop in bone marrow
precursors of plasma cells
first found in birds

Question 2

Immature B cells

Answer 2

get rid of self reactive cells, help prevent autoimmune diseases

Question 3

Mature B cells

Answer 3

membrane IgM and IgD, specific for same antigen

responsive to antigen

Question 4

Plasma cell

Answer 4

secretion of antibody isotype (primary - IgM, secondary- IgG)
found in lymphoid organs and bone marrow
elongated cell, eccentric nucleus, perinuclear halo, abundant cytoplasm
terminally differentiated antibody producing machines
lifespan is a few days

Question 5

Peak response for primary and secondary response

Answer 5

primary = smaller
secondary = larger

Question 6

Antibody isotype for primary and secondary response

Answer 6

primary = IgM > IgG
secondary = Increase in IgG, and sometimes IgA or IgE

Question 7

Antibody affinity in primary and secondary response

Answer 7

primary = lower average affinity, more variable
secondary = higher average affinity (affinity maturation)

Question 8

What are the primary and secondary responses induced by

Answer 8

primary = all immunogens
secondary = mainly protein antigens

Question 9

How does B lymphocyte react to protein antigen

Answer 9

bind by surface antibody
receptor mediated endocytosis
processed/expressed on class II MHC

Question 10

How does B lymphocyte react to non protein antigen

Answer 10

can’t be complexed to MHC proteins

Question 11

Variable region of heavy chain encodes what

Answer 11

V,D, and J gene segments

Question 12

Variable region of light chain encodes what

Answer 12

V and J gene segments

Question 13

How do we get diversity

Answer 13

pairing of heavy and light chains
combinatorial diversity
junctional diversity
somatic mutation

Question 14

combinatorial diversity

Answer 14

different gene segments rearranged

Question 15

junctional diversity

Answer 15

nucleotide addition/removal occurs at joints between gene segments

Question 16

somatic mutation

Answer 16

point mutations in variable regions of heavy and light chain gene segments that have been rearranged

Question 17

Co-expression of IgM and IgD

Answer 17

Primary RNA transcript contains VDJ region coupled to both Cmu and Cdelta
alternative mRNA splicing encode IgM and IgD, both specific for same antigen because they use the same VDJ region

Question 18

Production of secreted antibody forms

Answer 18

coded by primary RNA transcript
membrane anchoring sequences get spliced out, formed the secreted form
when B cells are stimulated by antigen it shifts to the secretory form

Question 19

Production of membrane antibody forms

Answer 19

coded by primary RNA transcript

Question 20

Isotype switching

Answer 20

Not random
long primary RNA transcript containing VDJ regions and many or all Ch sequences produced, followed by splicing out of unneeded Ch regions
another method is deletion of intervening Ch region genes to align VDJ regions with new Ch genes.

Question 21

affinity maturation

Answer 21

due to somatic mutations in V region genes
the lymphocytes that have the highest affinity get selected for
High affinity B cells bind to antigen, interact with Tfh cells, and produce high affinity antibody.

Question 22

TD antigens

Answer 22

thymus dependent

are protein antigens

Question 23

TI antigens

Answer 23

thymus independent
ex) polysacchardes, nucleic acids, lipids
provide all necessary B cell signals

Question 24

TI-1 antigens

Answer 24

bind non immunoglobulin receptors and promote polyclonal expansion

Question 25

TI-2 antigens

Answer 25

bind through B cell surface immunoglobulin