ch 4: overview of adaptive immunity

Question 1

describe some of the disadvantages of the innate system

Answer 1

the process of innate is limited in recognizing diverse pathogens due to lack of receptor diversity

Question 2

what is the adaptive immune response based on?

Answer 2

specificity and diversity, it focuses on targeting specific antigens

Question 3

what is the marker that innate immune receptors recgonize?

Answer 3

PAMPs

Question 4

adaptive immune cells recognize pathogens presented by ____ _____________

Answer 4

MHC molecules

Question 5

what is one of the biggest differences between innate and adaptive?

Answer 5

adaptive has immune memory, or the ability to say the system will respond much faster than normal to combat future infections

Question 6

describe T cell receptors

Answer 6

composed of two protein chains, alpha and beta or delta and gamma. each chain has a constant region (close to membrane) and variable region. the variable region is what holds the antigen binding site.

Question 7

each T cell receptor is capable of recognizing ____

Answer 7

one specific antigen

Question 8

peptides are presented to T cell receptors by ___________

Answer 8

MHC molecules

Question 9

differentiate MHC class I and II

Answer 9

• MHC I present intracellular antigens
• MHC II present extracellular antigens
• MHC I bind to CD8 coreceptors
• MHC II bind to CD4 coreceptors

Question 10

define immunoglobulins

Answer 10

act as B cell receptors, made up of two heavy chains and two light chains. they contain two antigen binding sites and can be present on the surface of a B cell or secreted by plasma cells. they also can recognize only one specific antigen.

Question 11

what makes immunoglobulins different from T cell receptors?

Answer 11

immunoglobulins do not require an MHC molecule to present an antigen and they can recognize any biological macromolecule (protein, carbohydrate, lipid, nucleic acid)

Question 12

what are the five major functions of soluble immunoglobulins?

Answer 12

• neutralization of foreign particle/pathogen
• opsonization of foreign particle/pathogen
• complement activation
• activation of innate immune cells (NK cells, mast cells)
• protection of internal/mucosal tissues

Question 13

what is MHC polymorphism

Answer 13

subtle changes in the protein produced by an MHC.

Question 14

why is MHC matching for transplants important?

Answer 14

it can help prevent the immune system from recognizing the transplant as foreign if the MHC matches the host MHC1

Question 15

why does adaptive require such a long period of time to respond?

Answer 15

• the diversity of T cell receptors and immunoglobulins means few T and B cells can recognize a new pathogen
• antigen needs to be delivered and presented in secondary lymphoid tissues and organs
• antigen specific B and T cells need to be activated, proliferated, and differentiated in secondary lymph nodes before they can migrate to sites of infection

Question 16

T cells mature in the _____ and B cells develop in the _________

Answer 16

thymus, bone marrow

Question 17

both T and B cells undergo ______ _________ to rearrange genes and test their functionality of receptors

Answer 17

somatic recombination

Question 18

describe antigen processing

Answer 18

• intracellular antigens, including those from intracellular pathogens such as viruses and Shigella bacteria, are digested in the cytoplasm
• extracellular antigens, including those from extracellular pathogens such as Vibrio cholerae bacteria, are digested within a phagolysosome

Question 19

dendritic cells present peptide fragments to T cells by which two processes

Answer 19

• cytosolic pathogen proteins are processed in the cytosol and presented to MHC I
• extracellular pathogen proteins are processed in phagolysosomes are presented to MHC II

Question 20

describe T cell clonal selection and expansion

Answer 20

the T cell receptor engages with the MHC molecule with the correct antigen and drives proliferation of the T cell. in MHC I, CD8 T cells differentiate into cytotoxic T cells. in MHC II, CD4 T cells differentiate into helper T cells.

Question 21

what do cytotoxic and helper T cells do?

Answer 21

cytotoxic T cells monitor intracellular infections and can target cells for destruction. helper T cells can migrate to parts of the lymph node to activate other cells such as B cells and macrophages to aid in infection

Question 22

how can B cells be differentiated?

Answer 22

cytokine signals from helper T cells can cause differentiation of B cells into plasma cells or memory B cells

Question 23

what is somatic hypermutation?

Answer 23

it is a random mutation at the variable regions of the immunoglobulin gene that drive altered affinity of that immunoglobulin for its antigen. the immunoglobulin gene is randomly altered in a subset of activated B cells to promote the production of B cells containing immunoglobulins with higher affinity for antigen. REFINEMENT OF ANTIBODY

Question 24

where do dendritic cells process foreign antigens?

Answer 24

draining lymphoid tissues

Question 25

in the absence of __________ and ________ B and T cell activation would not take place

Answer 25

dendritic cells, antigens

Question 26

rearrangement

Answer 26

• combination of different subunits (alpha and beta chain for T cell receptors, and heavy and light chain for B cell receptors) result in receptor diversity
• occurs only in developing T and B cells

Question 27

T cell receptor rearrangement

Answer 27

• alpha chain has variable regions linking V and J
• beta chain has variable regions linking V, D and J

Question 28

B cell receptor rearrangement

Answer 28

• heavy chain contains V, D and J segments
• light chain contains V and J segments
• 5 different constant regions that can be used as heavy chain components for isotype switching

Question 29

where are RSSs found?

Answer 29

at the downstream ends of V segments, both the upstream and downstream ends of D segments, and the upstream end of J segments

Question 30

structural features of RSSs that that allow for V(D)J recombination events to occur specifically and efficiently at lymphocyte receptor genes

Answer 30

• conserved heptamer
• conserved nonamer (farthest from coding segment)
• a spacer (23 or 12 bp) (provide full DNA helix twist)

Question 31

function of TdT

Answer 31

ability to add additional nucleotides known as N nucleotides before the segments are joined together through DNA repair

Question 32

what is class switch recombination?

Answer 32

change to the constant region (B cell specific)

Question 33

key proteins in VDJ recombinase?

Answer 33

RAG1 and RAG2 which bind and recognize RSSs that border V, D, and J DNA segments

Question 34

positive selection

Answer 34

selects cells with functional receptors

Question 35

negative selection

Answer 35

selects against cells with self-reactive receptors

Question 36

describe positive selection

Answer 36

binding -> cell proceeds to next step in development
no binding -> cell dies by apoptosis

Question 37

describe negative selection

Answer 37

tight binding -> cell dies by apoptosis
moderate/weak binding -> cell survives and proceeds to next step

Question 38

describe the three MHC classes

Answer 38

• class I: present peptides from proteins made inside the cell
• class II: present peptides from extracellular proteins taken into phagolysosomes
• class III: immune regulatory proteins and some complement proteins

Question 39

describe MHC I presentation

Answer 39

• proteins in cytoplasm digested by proteasome into peptide fragments
• fragments are transported into ER and loaded onto MHC I molecules
• MHC I peptide complex exists the ER and travels to plasma membrane via secretory pathway
• CD8 T cell recognizes the complex and activates it on cell surface

Question 40

describe MHC II presentation

Answer 40

• MHC class II molecules translated and transported into ER
• MHC class II molecules travel through the secretory pathway to a secretory vesicle, where they wait for further action driven by a phagolysosome
• extracellular molecules and pathogens are endocytosed by professional APCs, including macrophages, dendritic cells, and B cells
• endosome containing the extracellular material matures into a phagolysosome, which results in the digestion of proteins by lysosomal proteases
• phagolysosomes fuse with secretory vesicles containing MHC II, which can bind to peptides generated during lysosomal digestion
• newly loaded MHC II travel to the cell surface where they present peptides generated by the digestion of extracellular material to T cells

Question 41

CD3 complex

Answer 41

formed through the association of T cell receptors and other transmembrane proteins with cytoplasmic tails with signaling motifs to create T cell receptor signaling that activates T cells

Question 42

naive B cells initially secrete ____

Answer 42

IgM

Question 43

naive B cells can undergo class switching to produce _____, _____, or _____

Answer 43

IgG, IgA, IgE

Question 44

Ig-alpha and Ig-beta

Answer 44

the two proteins B cell receptors associate with that have cytoplasmic domains and signaling motifs