chapter 27 - adaptive immunity

Question 1

What is innate immunity?

Answer 1

broadly targeted responses triggered by common structural features on microoorganisms

Question 2

What is adaptive immunity?

Answer 2

directed toward specific molecular components of microbes mediated by special class of antigen-reactive leukocytes called lymphocytes

Question 3

What are B lymphocytes?

Answer 3

display antigen-specific receptors adhere surface, defend against intracellular pathogens
conferring cellular immunity to host

Question 4

What is specificity?

Answer 4

dependent on lymphocyte receptors interacting with individual antigens

Question 5

What is the difference between T-cells and B cells?

Answer 5

Tcells: antigen-specific recepots
B: membrane-bound immunoglobulins on surface.

Question 6

What is memory?

Answer 6

first antigen exposure induces multiplication of antigen reactive cells creating multiple clones.

Question 7

What is the primary immunoglobulin response?

Answer 7

first exposure to an antigen, antigen recognition done by specific B of T lymphocytes

Question 8

What is the secondary immunoglobulin response?

Answer 8

subsequent exposure to same antigen activates clones from primary immunoglobulin response, generating faster response.

Question 9

What is tolerance?

Answer 9

acquired ability to make an adaptive response to discriminate between host and foreign antigens

Question 10

What is autoimmunity?

Answer 10

failure to develop tolerance that may result to reaction against self.

Question 11

What is positive selection?

Answer 11

T cell recognize MHC peptides are retained

Question 12

What is negative selection?

Answer 12

T cells pass positive selection and strongly bind to self-antigens

Question 13

When does positive B cell selection occur?

Answer 13

When B cell receptors encounter an antigen that they recognize.

Question 14

What happens when B cell receptors recognize an anitgen?

Answer 14

1. They proliferate, make more copies
2. They differentiate into antibody-producing plasma cell and few memory cells
3. negative b cell selection occurs in bone marrow, self-reactive B cells are deleted

Question 15

What are antigens?

Answer 15

substances that react with antibodies or T cell receptors

Question 16

What are immunogens?

Answer 16

substances that elicit an immune response (not all antigens are immunogens)

Question 17

What intrinsic factors determine immunogenicity?

Answer 17

1. size: happens (small molecules that aren’t immunogens, but can induce immune response if attached to large carrier molecule)
2. complexity: complex proteins and carbs are good immunogens, simple repeating DNA are poor immunogens
3. physical form: insoluble molecules or aggregates are usually excellent immunogens

Question 18

What extrinsic factors determine immunogenicity?

Answer 18

1. dose: micrograms to grams
2. route: injection is more effective than oral
3. large oral does of immunogens: can cause tolerance rather than immunity.

Question 19

What are antibodies?

Answer 19

They don’t interact with entire antigen, only with distinct portion of molecule called antigenic determinant or epitope
(T-cell receptors recognize epitope only after antigen has been processed)

Question 20

What is an example of natural active immunity?

Answer 20

immune system responds to an active infection (measles)

Question 21

What is an example of artificial active immunity?

Answer 21

immune system responds to antigens present in vaccines

Question 22

What is an example of natural passive immunity?

Answer 22

antibodies transferred from mother to infant in breast milk

Question 23

What is an example of artificial passive immunity?

Answer 23

venom in rattlesnake can be neutralized by antibodies

Question 24

What characteristics define active immunities?

Answer 24

1. exposure to antigen through immunity through administration or infection
2. specific immune response made by immunity
3. activated by antigen (immune memory in effect)
4. maintained via stimulation of memory cells
5. develops over weeks

Question 25

What characteristics define passive immunities?

Answer 25

1. no exposure to antigen, immunity achieved by injecting antibodies or antigen-reactive T cells. 2. specific immune response made by donor of antibodies or T cells. 3. no immune system activated, no immune memory 4. cannot be maintained, decays rapidly 5. develops immediately

Question 26

How do B lymphocytes help the body?

Answer 26

- a B cell has 100,000 identical antibodies on its surface called B cell receptors - B cell receptors bind to antigen and internalize it and digest it - B cells then interacts with an antigen specific T cell (T helper cell) which secretes cytokines to activate B cell to produce clones that differentiate into plasma membrane

Question 27

What is the function of an antibody?

Answer 27

they are either soluble or cell surface antigen receptor, where they can bind to toxins or viruses to neutralize them. They can also bind to foreign cells and make them easier to engulf by phagocytes.

Question 28

What are the 5 major classes of antibodies?

Answer 28

1. IgG: most common, 4 polypeptide chains (2 heavy and 2 light) has 2 antigen-binding sites 2. IgA: dimers, present in body fluids (tears, saliva, breast milk) 3. IgM: aggregate of 5 immunoglobulin molecules 4. IgD: present in serum, has no known function 5. IgE: found in serum, functions as antibody binds to eosinophils

Question 29

What is the primary antibody response?

Answer 29

produces short-lived plasma cells that live less than a week (mostly IgM)

Question 30

What is the secondary antibody response?

Answer 30

response quicker (memory cells don't need T cell help. produces 10-100 times more antibodies (IgG)

Question 31

What are complementarity-determining regions (CDR)

Answer 31

variable domains of different antibodies are different from one another

Question 32

What is binding?

Answer 32

function of folding pattern of heavy and light polypeptide chains

Question 33

What is binding affinities?

Answer 33

different antibodies bind their epitopes with different strengths

Question 34

What are the multiple unknown mechanisms that generate antibody diversity?

Answer 34

1. somatic recombination 2. random heavy + light chain reassortment 3. coding for joint diversity 4. hypermutation

Question 35

What happens while gene rearrangement by somatic recombination?

Answer 35

as B cell matures, immunoglobulin gene segments undergo random rearrangements by recombination and deletion once the rearrangement is successful, process stops.

Question 36

What is allelic exclusion?

Answer 36

only rearranged allele is expressed so that each B cell produces 1 antibody

Question 37

What is the mechanism of the reassortment of heavy chains?

Answer 37

1. there are two light chains, kappa and lambda 2. 5 heavy chains join either kappa or lambda to form an antibody 3. gene reassortment can generate more than 3.3 million antibodies

Question 38

What is somatic hypermutation?

Answer 38

mutation rate of B cell immunoglobulin gene is higher than other genes

Question 39

What is affinity maturation?

Answer 39

B cells with receptors displaying higher affinity for the antigen are selected.

Question 40

What are MHC class I proteins and what do they do?

Answer 40

They are proteins found on surface of ALL nucleated cells 1- present internal antigens to T-cytotoxic cells, internal antigens can originate from viral proteins or cancer proteins. 2 - if peptide is recognized by T cell receptor, antigen containing cell is destroyed. there are major antigen barriers for tissue transplants.

Question 41

What are MHC class II proteins and what do they do?

Answer 41

They are proteins found on surface of antigen-presenting cells (B lymphocytes or macrophages) 1- present antigen to T-helper cells 2- stimulate cytokine production and leas to antibody-mediated immunity or inflammatory responses.

Question 42

What is the antigen presentation by MHC I proteins?

Answer 42

1. protein antigens degraded by proteasome in cytoplasm 2. peptide fragments transported into endoplasmic reticulum through TAP proteins 3. MHC I proteins are stabilized by chaperonins 4. When peptide fragments bind MHC I, complex moves to cell surface and interacts with CD8 5. T cytotoxic cell activated by the binding events causing to release cytokines and cytolytic toxins and kill target cells.

Question 43

What is the antigen presentation by MHC II proteins?

Answer 43

1. external proteins imported into cell, MHC II binds foreign peptide fragments 2. MHC II peptide complex transported to cell surface, interacts with CD4 3. T helper cells release cytokines that interact with other cells promoting immunity 4. antigen-presenting cell in pathway can be B lymph. that ingest antigens by endocytosis or macrophages which engulfs antigens through phagocylosis.

Question 44

How does T cell-mediated immunity work?

Answer 44

1. antigen presenting cells in innate immunity ingest, degrade and proccess antigens. 2. they present antigens to T cells that secrete protein cytokines that activate immune response 3. T-helper cells produce and release cytokine that indices inflammation. 4. T-cytotoxic cels produce and release perforin and granzyme for target cell lysis 5. T cells dont interact with foreign antigen (unless presented with MHC) T cell receptors bind only to MHC molecules having foreign antigens embedded in MHC protein.W

Question 45

How is the diversity of T cell receptors generated?

Answer 45

1. somatic recombination 2. random chain reassortment 3. coding for joint diversity/

Question 46

What are immunoglobulin gene superfamily?

Answer 46

immunoglobulins, T cell receptors and MHC proteins

Question 47

What do immunoglobulin gene superfamily consist of?

Answer 47

1. two nonidentical polypeptide chains 2. constat and variable regions 3. share protein domain 4. similar mechanism generating diversity for immunoglobulins and T cell receptors.