6: Antibody structure

Question 1

3 main functions of antibodies

Answer 1

• opsonization
• complement activation
• neutralization

Question 2

opsonization examples (2)

Answer 2

• phagocytosis
• eosinophil dumps toxic products to kill parasite
• coating antigen with antibody enhances phagocytosis

Question 3

complement activation

Answer 3

series of proteins activated by antibody binding to surface –> punch holes in bacteria
-inflammation and cell lysis

Question 4

neutralization

Answer 4

secreting products onto virus/bacteria to block adhesion to mucosa

Question 5

what is adaptive/acquired immunity

Answer 5

the specific response to antigenic challenge

Question 6

what is adaptive immunity mediated by

Answer 6

antigen-specific lymphocytes and/or their products

Question 7

5 steps of the immune response

Answer 7

• innate immunity
• early induced response
• late adaptive response
• protective immunity
• immunological memory

Question 8

steps of innate immunity

Answer 8

innate immunity –> infection –> recognition by non-specific effectors –> pathogen clearance

Question 9

steps of early induced response

Answer 9

early induced response –> infection –> recruitment of effector cells –> activation of effector cells –> pathogen clearance

Question 10

steps of late adaptive response

Answer 10

late adaptive response –> infection –> antigen transport to lymphoid organs –> recognition by native b and t cells –> clonal expansion of b and t cells –> pathogen clearance

Question 11

steps of protective immunity

Answer 11

-protective immunity –> re-infection –> recognition by preformed antibody and effector t cells –> pathogen clearance

Question 12

steps of immunological memory

Answer 12

immunological memory –> re-infection –> recognition by memory b and t cells –> rapid expansion to effector cells –> pathogen clearance

Question 13

when does antibody production initiate

Answer 13

3-7 days after initial exposure if the innate immune processes fail to clear it rapidly

Question 14

what are antibodies

Answer 14

antigen-specific products of b cells –> principal mediators of adaptive immunity

Question 15

antibody structure

Answer 15

• 2 identical heavy chains, 2 identical light chains
• variable and constant regions
• 2 binding sites on top of light chains

Question 16

how do antibodies interact with antigens

Answer 16

non-covalently

Question 17

how are antibodies divided into isotypes (classes)

Answer 17

different constant regions –> heavy chain weight gives different properties (heavy chain is the constant region)

Question 18

types of antibodies made by b cells

Answer 18

• different b cells make different antibodies

- a single b cell makes all the same antibodies

Question 19

how are distinct antibody regions determined

Answer 19

by protease digesion –> Fc portion contains heavy chain constant region, Fab portion contains the antigen binding site

Question 20

what are Fc and Fab

Answer 20

• Fc: fragment of crystalization

- Fab: fragment of antigen binding

Question 21

how are different antibody regions defined

Answer 21

• proteolytic digesion

- function

Question 22

where are antibodies assembled

Answer 22

in the b cell

Question 23

where does antigen binding occur

Answer 23

binding site at junction of variable heavy chain and variable light chain

Question 24

valency of antibodies

Answer 24

multivalent –> can bind 2 of the same epitopes on a single antigen or 2 of the same epitopes on different antigens

Question 25

types of antibody differences (3)

Answer 25

- isotypic differences (IgG v IgA) - allotypic differences (different alleles but both IgG) - idiotypic differences (binding site differences)

Question 26

difference between b cell and mature plasma cell

Answer 26

- b cell has antibodes on cell surface - plasma cell secretes antibodies - plasma cell is a b cell that secretes antibodies

Question 27

what immunoglobulin is always secreted first by a b cell

Answer 27

IgM

Question 28

what Ig are secreted onto mucosal surfaces and protected from degradation by binding to the J chain

Answer 28

IgM and IgA

Question 29

how are IgM and IgA secreted

Answer 29

- IgM as a pentomer - IgA as a dimer - antigen specificity of antigen binding site is identical for both

Question 30

purpose of J chain

Answer 30

used to transport dimeric IgA across epithelial barriers to coat mucosal surfaces

Question 31

what does the variable region confer

Answer 31

epitope specificity

Question 32

what does the Ig constant region confer

Answer 32

functional capacity

Question 33

what does allelic exclusion result in

Answer 33

only 1 chromosome rearrangement per cell

Question 34

what is IgM known for

Answer 34

complement activity

Question 35

what is IgD known for

Answer 35

not fucking much

Question 36

what is IgG known for

Answer 36

basically everything (opsonization, crosses placenta, extravascular diffusion) --> phagocytosis

Question 37

what is IgA known for

Answer 37

mucosal --> crosses epithelium

Question 38

what is IgE known for

Answer 38

mast cell activation

Question 39

what are isotypes encoded by

Answer 39

a cluster of heavy chain genes

Question 40

what influence which isotype is expressed

Answer 40

cytokines

Question 41

consequences of inherited IgA deficiency

Answer 41

no antibodies on lung surface --> URI

Question 42

what connects variable and heavy chains together

Answer 42

hinge --> gives flexibility

Question 43

how is the region of the antibody gene that binds to the epitope generated

Answer 43

by a semi-random rearrangement of gene segments --> different exons for the antibody chains within each b cell (more variation = more things recognized)