Humoral Immunity

Question 1

complement system

Answer 1

set of interacting proteins released into the blood after production in the liver.

has two pathways of activation, enhances inflammation, enhances phagocytosis by opsonization, causes lysis of particles by membrane pore formation, removes extracellular pathogens

both pathways produce anaphylatoxins (C3a, C4a C5a). C5a is also chemotactic.

Question 2

alternative pathway of complement activation

Answer 2

completely innate, does not require antibody to initiate, C3 spontaneously lysis in serum and C3b finds surface of bacteria, forms membrane attack complex, major opsonin

Question 3

classical pathway of complement activation

Answer 3

activated by antigen-antibody complexes (ex. IgM or IgG)

cleavage of C3 results in recruitment of inflammatory cells, opsonization of pathogens, and perforation of pathogen cell membranes

Question 4

Inappropriate activation of the complement cascade is controlled at the level of

Answer 4

C1, C3, and C5

Question 5

Contact between B and T helper cells involves

Answer 5

MHC class 2/peptide presentation, costimulatory molecules (B7/CD28), CD40/CD40L binding, and cytokine production (IL-2, IL-4, IL-5, IL-6)

cytokines induce differentiation, memory cell, class switching

Question 6

costimulatory molecules (B7:CD28)

Answer 6

needed for T-cell activation

Question 7

CD40/CD40 Ligand binding

Answer 7

needed for B cell class switching and memory response

Question 8

Papain cleavage

Answer 8

results in 2 Fab and 1 Fc, cannot agglutinate, each part can only bind to single antigen

Question 9

Pepsin cleavage

Answer 9

results in one divalent molecule, can bind 2 antigen, can still agglutinate

Question 10

avidity

Answer 10

increases with number of binding sites. IgM has greater avidity than IgG because it is secreted as a pentamer

Question 11

idiotype

Answer 11

defines antigen specificity, determined by variable region

Question 12

isotype

Answer 12

dictates effector functions, constant region

Question 13

IgM

Answer 13

first antibody made, secreted as pentamer that is joined together by J chains, can bind 10 antigens, traps free antigen, activates complement, low affinity (weaker binding strength) to antigen compared to IgG, cannot act as opsonin

Question 14

class switching (what it requires, when it occurs, where it occurs)

Answer 14

requires: T-cell, CD40 Ligand, Cytokines, occurs only during immune response, happens in germinal center in secondary lymphoid tissues

result of recombination within constant region. antigen specificity unchanged. dependent on AID (activation induced cytidine deaminase).

Question 15

somatic hypermutation

Answer 15

random mutations in the coding of the variable domain region, creates single point mutations in the antibody idiotype which can increase affinity

occurs after b cell is activated by antigen, does not affect constant region, dependent on AID (activation induced cytidine deaminase) enzyme

Question 16

TH2 cell release of cytokine

Answer 16

induces the differentiation of B cells into fully differentiated, antibody-secreting cells and memory cells and induce class switching

Question 17

thymus-independent antigens

Answer 17

antigens contain no peptides, stimulates secretion of IgM antibodies only and does not result in immunologic memory

Question 18

germinal centers

Answer 18

clones of proliferating antigen specific B cells, where somatic hypermutation occurs, follicles of the lymph nodes and spleen

Question 19

clonal selection

Answer 19

results in affinity maturation, predominance of clones capable of producing antibodies with increasing affinity for the antigen

Question 20

isotype switching

Answer 20

changing the heavy chain constant domains to classes of antibodies with new and different effector functions. rearranges the DNA encoding the constant region of the heavy chain. one way reaction.

Question 21

IgG

Answer 21

activates complement, opsonizes, mediates ADCC, can be transported across placenta which protects fetus during gestation

has a gamma heavy chain,

Question 22

IgA

Answer 22

exists as dimer, protective defense of the mucosal surfaces of the body, not opsonin

neutralization, crosses epithelium, present in urinary and gut, predominate class in secretions

Question 23

B cell activation requires

Answer 23

needs to enter lymphoid follicles and be stimulated by antigen with T cell help to become activated

Question 24

thymus independent 1 (TI-1) antigen

Answer 24

such as LPS can activate a B cell by replacing T-cell signals with TLR4 (toll receptor). This results in antibodies specific for LPS.

no immunologic response, no memory B cells, no IgG, only IgM response, responses are short lived

Question 25

thymus independent 2 (TI-2) antigen

Answer 25

can activate a B cell by cross linking receptors to produce a strong signal, enough to activate a B cell.

no immunologic response, no memory B cells, no IgG, only IgM response, responses are short lived

Question 26

follicular dendritic cell

Answer 26

holds antigen without processing them so B cells can examine antigen and become activated

Question 27

endotoxin

Answer 27

heat stable, toxicity not destroyed by sterilization techniques, detected using Limulus Amebocyte Lysate

Question 28

opsonization

Answer 28

enhances phagocytosis, occurs when specific antibodies are present

Question 29

eosinophil

Answer 29

clears parasitic worms, releases granule contents to kill antibody coated parasites

Question 30

neutrophils

Answer 30

engulf and kills bacteria in infected tissue, does not undergo cell division, enters tissue during inflammation, contains granules with bacterial and hydrolytic enzymes

Question 31

macrophage

Answer 31

derived from bone marrow, circulates in blood, capable of intracellular and extracellular killing

Question 32

natural killer cells

Answer 32

kills cells that don’t present MHC class I, large granular lymphocytes, kills cells infected with certain viruses

Question 33

common lymphoid progenitor

Answer 33

B cell, T cell, NK cells

Question 34

myeloid progenitor

Answer 34

neutrophil, eosinophil, basophil

Question 35

lag (inductive/latent) phase

Answer 35

period of time before any antibodies are made/detected

Question 36

steady state

Answer 36

when peak antibody concentration is reached

Question 37

secondary response vs primary response

Answer 37

faster response, higher rate of antibody synthesis, increased response, increased half life of antibodies, mostly IgG, antibodies have higher affinities, less antigen needed to provoke response

Question 38

clonal expansion

Answer 38

when a single B-cells proliferates with T cell help

Question 39

clonal selection theory

Answer 39

each naive B cell produces an immunoglobin of unique specificity

Question 40

RAG 1 and RAG 2

Answer 40

recombinase genes that are needed to recombine V, D, J segments. cleaves heptamer from D and J segments, opens up DNA hairpins. RAG is sloppy and leaves pieces of DNA

no RAG means no T or B cells. no rearrangement of genes to express immunoglobins

Question 41

TdT (terminal deoxynucleotidyl transferase)

Answer 41

randomly adds nucleotides, only exists at certain times of the life cycle

no TdT means less diversity, antibodies with lower affinities to antigen (no random mutations)

Question 42

Antibodies expressed on naive B cell that has never encountered antigen

Answer 42

IgM and IgD only

Question 43

somatic recombination

Answer 43

occurs during development of B cells. arrays of V, D, and J segments are cut and spliced by DNA recombination

Question 44

heavy chain

Answer 44

heavy chain locus on chromosome 14. requires 2 recombinations. 1st D and J, then DJ and V.

Question 45

light chain

Answer 45

kappa on chromosome 2, gamma on chromosome 22. single recombination needed. V and J.

Question 46

junctional diversity

Answer 46

addition of P and N nucleotides with help of TdT and RAG

Question 47

diversity in V region sequences

Answer 47

random combination of VJ in light chain and VDJ in heavy chain, junctional diversity (introduction of nucleotides at junctions between segments during recombination), association of heavy and light chain in different combinations

Question 48

less mature B cell

Answer 48

only one of the following is rearranged (light and heavy chain)

Question 49

IgE

Answer 49

sensitization of mast cells, immediate hypersensitivity