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microbiology final > chapter 27 - adaptive immunity > Flashcards

chapter 27 - adaptive immunity Flashcards

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Biology 101 flashcards
1
Q

What is innate immunity?

A

broadly targeted responses triggered by common structural features on microoorganisms

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2
Q

What is adaptive immunity?

A

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

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3
Q

What are B lymphocytes?

A

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

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4
Q

What is specificity?

A

dependent on lymphocyte receptors interacting with individual antigens

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5
Q

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

A

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

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6
Q

What is memory?

A

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

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7
Q

What is the primary immunoglobulin response?

A

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

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8
Q

What is the secondary immunoglobulin response?

A

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

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9
Q

What is tolerance?

A

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

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10
Q

What is autoimmunity?

A

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

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11
Q

What is positive selection?

A

T cell recognize MHC peptides are retained

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12
Q

What is negative selection?

A

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

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13
Q

When does positive B cell selection occur?

A

When B cell receptors encounter an antigen that they recognize.

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14
Q

What happens when B cell receptors recognize an anitgen?

A
  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
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15
Q

What are antigens?

A

substances that react with antibodies or T cell receptors

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16
Q

What are immunogens?

A

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

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17
Q

What intrinsic factors determine immunogenicity?

A
  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
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18
Q

What extrinsic factors determine immunogenicity?

A
  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.
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19
Q

What are antibodies?

A

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)

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20
Q

What is an example of natural active immunity?

A

immune system responds to an active infection (measles)

21
Q

What is an example of artificial active immunity?

A

immune system responds to antigens present in vaccines

22
Q

What is an example of natural passive immunity?

A

antibodies transferred from mother to infant in breast milk

23
Q

What is an example of artificial passive immunity?

A

venom in rattlesnake can be neutralized by antibodies

24
Q

What characteristics define active immunities?

A
  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
25
Q

What characteristics define passive immunities?

A
  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
26
Q

How do B lymphocytes help the body?

A
  • 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
27
Q

What is the function of an antibody?

A

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.

28
Q

What are the 5 major classes of antibodies?

A
  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
29
Q

What is the primary antibody response?

A

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

30
Q

What is the secondary antibody response?

A

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

31
Q

What are complementarity-determining regions (CDR)

A

variable domains of different antibodies are different from one another

32
Q

What is binding?

A

function of folding pattern of heavy and light polypeptide chains

33
Q

What is binding affinities?

A

different antibodies bind their epitopes with different strengths

34
Q

What are the multiple unknown mechanisms that generate antibody diversity?

A
  1. somatic recombination
  2. random heavy + light chain reassortment
  3. coding for joint diversity
  4. hypermutation
35
Q

What happens while gene rearrangement by somatic recombination?

A

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

36
Q

What is allelic exclusion?

A

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

37
Q

What is the mechanism of the reassortment of heavy chains?

A
  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
38
Q

What is somatic hypermutation?

A

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

39
Q

What is affinity maturation?

A

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

40
Q

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

A

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.

41
Q

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

A

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.

42
Q

What is the antigen presentation by MHC I proteins?

A
  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.
43
Q

What is the antigen presentation by MHC II proteins?

A
  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.
44
Q

How does T cell-mediated immunity work?

A
  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
45
Q

How is the diversity of T cell receptors generated?

A
  1. somatic recombination
  2. random chain reassortment
  3. coding for joint diversity/
46
Q

What are immunoglobulin gene superfamily?

A

immunoglobulins, T cell receptors and MHC proteins

47
Q

What do immunoglobulin gene superfamily consist of?

A
  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.
48
Q
A

microbiology final (20 decks)

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