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Microbiology > Adaptive Immune System > Flashcards

Adaptive Immune System Flashcards

1
Q

What are the two types of adaptive immunity?

A

Antibody mediated or cell mediated

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2
Q

Descrive adaptive immunity’s memory

A

Its a faster, bigger response - especially if the organism is encountered more than once and its specific for a given organism

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3
Q

What is an antigen

A

an antibody generator

  • any molecule that reacts specifically with the Ag or Ab receptor on a lymphocyte
  • does not necessarily have to initiate an immune response
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4
Q

What is an immunogen

A

An antigen that specifically induces and immune response

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5
Q

What do we want to do for an antigen to work as a vaccine?

A

We want to evoke a high level of immunogenicity

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6
Q

What is an epitope

A

its an antigenic determinant

  • they’re specific regions of the antigen that are specifically recognized by the adaptive immune response
  • usually a stretch of 10 or more AA
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7
Q

Descrive antibody mediated (or humoral) immunity

A
  • the antibody is the main immune cell
  • neutralizes free-floating particles (bacteria, toxins, viruses)
  • in response to extracellular antigens, the B cells are triggered t proliferate and differentiate into plasma cells
  • Y shaped proteins are then called antibodies
  • some B cells here form memory cells that respond faster when exposed to the same antigen again
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8
Q

Where are antibodies produced

A

produced by B lymphocytes (B cells) in the bin marrow of humans or the bursa of birds

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9
Q

What are the 2 structures of an antibody?

A

2 arms (identical) and a stem

Arms: bind to a specific antigen
Stem: tags the antigen for destruction by other immune system components

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10
Q

What are the two types of antibodies?

A

Light chain and heavy chain

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11
Q

What are IgG antibodies made up of?

A
  • made of 75% of serum immunoglobulins
  • has basic monomeric structure
  • 4 subclasses based on AA sequence of the C regions of H chains (IgG1-4)
    IgG1 is most prevalent
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12
Q

What part of the antibody does the phagocyte recognize?

A

The heavy chain

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13
Q

What are the functions of IgG antibodies

A
  • opsonization - enhances phagocytosis, acts as a flag for phagocytes with Fab is bound to the antigen and Fc is freely exposed
  • neutralizes viruses and toxins
  • main Ab in secondary response when body encounters Ag for 2nd time
  • crosses the placenta- passive immunity for fetus from the mother
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14
Q

What are the structure of IgM antibodies

A

monomeric, when attached to the B cell surface as a receptor

- pentameric in serum, 5 monomers held together by a J chain

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15
Q

What are the function of the IgM antibodies?

A
  • the first antibody produces in the primary response
  • Ag recepts on B cells
  • activates part of innate defences
  • agglutinates particles (bacteria)- can do this because of its pentameric form
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16
Q

How do we know based on antibodies whether or not a person has been infected by a pathogen for the 1st time or the 2nd time?

A
  • if only IgM is in the body, we know that the infection in recent
  • if we see IgG, we know the infection has been around for a while
    (secondary response gives a high concentration of IgG molecules)
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17
Q

What is the structure and function of IgD antibodies

A

Structure: monomeric form, found in serum and on B cell surface as a receptor
- less than 2% of total serum antibodies are IgD
Function: unknown!

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18
Q

What is the structure of IgA antibodies and where are they found?

A
  • produced by mucous membranes secretions

- low amount of monomeric form in serum- dimeric form found in secretions

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19
Q

What are the functions of IgA antibodies?

A
  • neutralized bacteria and viruses, preventing them form attaching to mucous membranes
  • gives passive immunity from breast milk
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20
Q

What is the structure and function of IgE antibodies?

A
  • monomeric form, low levels found in serum
  • Ag receptors on mast cells (tissues) and basophils (in blood)
    Function: anaphylactic hypersensitivity
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21
Q

How can antibodies protect against viruses?

A

the virus can bind to a specific receptor in the host cell and cause infection this way - but if the antibody binds to the receptor and blocks the attachment, the virus will be stopped
- antibodies can protect from toxins the same way as well (by binding to a specific receptor)

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22
Q

What do tetanus shots give us?

A

Tetanus shots give a small amount of clostridium tent toxin - so that id the body becomes infected with this bacteria, the body would be immune to the effects of the toxin but NOT immune to the effects of the bacteria

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23
Q

What kind of immunity does T cells bring and were do they mature?

A
  • bring cell mediated immunity and mature in the thymus
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24
Q

Do T lymphocytes recognize free antigens?

A

No, they do not. They recognize antigens if they are presented by one of the body’s own cells
(bacterial or virally infected cells, transplant tissues, cancer)

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25
Q

How do T lymphocytes work?

A

They bind to the complex of MHC molecules and peptides
- T lymphocytes are activated from here
- T lymphocytes help macrophages kill intracellular parasites
- Th1 cells + MHCClass 2 -> Tcell release macrophage activating factors (interferon gamma)
No radicals involved
- T cells are active ONLY against foreign antigens

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26
Q

What are the 2 major functional populations of T cells

A
  • cytotoxic T cells

- helper T cells

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27
Q

Describe cytotoxic T cells

A
  • differentiate into Tc which destroy infected or cancerous cells -CD8
  • recognize Ag presented by MHC class 1 molecules
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28
Q

Describe helper T cells

A
  • differentiate into Th which activate B cells and macrophages - CD4
  • Th1 activate macrophages
  • Th2 activate B cells
  • recognize Ag presented by MHC class 2 molecules
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29
Q

What are MHC molecules?

A

molecules that present foreign molecules to T lymphocytes

30
Q

Descrive HIV

A

HIV recognizes CD4 molecules

  • host for HIV is helper T cells
  • called a syndrome because it doesn’t kill the patient, it only suppresses the immune system which makes the patient more susceptible to infections that can cause them to die
31
Q

What is the role of T lymphocytes?

A
  • T lymphocytes help macrophages kill parasites
    (Th1 cells + Class 2 MHC -> T cells release macrophage activating factors- interferon game)
  • no radicals!
  • T lymphocytes inhibit cellular replication of viruses (viral infected cells express MHC1 - recognized by Tc cells)
32
Q

How do macrophages get help from T lymphocytes?

A

T lymphocyte binds to the macrophage and tells the macrophage to kill the pathogen
- IFNgamma by the helper T cell is released, and the macrophage engulfs and kills the pathogen)

33
Q

How does the body combat large infectious agents?

A
  • by using antibody dependent cellular toxicity
  • effector cells can bind through their surface receptors to Ab molecules coating the target cells
  • activation of effector cells
  • release of material damaging targets (macrophages, eosinophils, NK cells)
34
Q

What is the lymphoid system designed to do?

A
  • designed to bring B and T cells in contact with Ags that enter the body
  • lymphocytes are highly specific, only recognizing 1 or 2 antigens
35
Q

What do the lymphatic vessels do?

A

Carry lymph collected from fluid that bathe the body’s tissues

  • lymph goes into surrounding tissues and supply them with oxygen and nutrients from blood
  • most fluid reenters capillaries and returns to the heart and lungs, but some enters the lymphatic vessels and travels to the lymph nodes where cells and proteins are removed
36
Q

What are the primary lymphoid organs?

A
  • bone marrow and thymus
  • hematopoitic stem cells develop into B and T cells
  • both B and T cells originate in bone marrow, but only B cells mature there
  • T cells mature in the thymus
37
Q

What do lymphocytes do in the secondary lymphoid organs?

A

gather to collect antigens

38
Q

What are the secondary lymphoid organs?

A

lymph nodes, spleen, tonsits, adenoids, appendix

39
Q

Where are lymphoid system organs located?

A
  • lymph nodes capture Ags from lymph

- spleen captures Ags from blood

40
Q

What is MALT and SALT

A

MALT: mucosal associated lymphoid tissue
- plays a key role in adaptive IR that prevents microbes from invading mucosal surface
SALT: skin-associated lymphoid tissue
- prevents microbes from invading skin

41
Q

How do B and T cell receptors differ?

A

They differ in surface markers - CD molecule (Cluster of differentiation)

42
Q

What is the B cells receptor?

A

The surface immunoglobulin

43
Q

What is the T cell receptor?

A

TCRs

44
Q

Describe colonial selection in B lymphocytes

A
  • only B cells that are capable of making correct antibody can bind to the antigen
45
Q

Describe colonial expansion in B lymphocytes

A
  • cells that bind antigens begin dividing, producing a population of clones
  • somatic mutations allow for further selection
  • – the reaction between the B cell and an antigen is the signal that allows the B cells to start dividing (have more B cells that recognize the same antigen)
46
Q

Do B lymphocytes require 2nd opinions in colonial expansion?

A

Yes! They require an accessory signals from another Th cell before activation can occur
- helps prevent the immune system from mounting the response against “self”

47
Q

What is a good way of determining an infection in a patient?

A

can look to see if a patient has a particular antibody for an antigen (whooping cough) -can use this because the production of antibodies will go up with a specific antigen

48
Q

Are colonial selection and expansion of B and T cells different?

A

No! Very similar - the only difference between B and T memory cells is their surface antigens

49
Q

What are the surface antigens on T memory cells

A

CD45RO

50
Q

What are the surface antigens on B memory cells

A

CD25 and surface IgG, IgA, or IgE

51
Q

How do B memory cells have a greater combining power?

A

Through mutation and selection

52
Q

How do T memory cells have a greater combining power?

A

through increased expression of accessory adhesion molecules

53
Q

What activates the classical complement pathway?

A

the binding of the antibody to the antigen

54
Q

Explain the events in the classical complement pathway in adaptive immunity?

A
  • the antibody binds to the antigen- this activates the C1 protein
  • coverts it to C1qrs - splits C2 and C4, forming C4b2a (this is similar to C3bBb in alternative pathway and is also known as a C3 convertase)
  • C3 convertase splits C3 into C3b and C3a
  • C3b binds to microbe Ab complex and remaining components join in (C5b, C6,7,8,9) to form a MAC attack
55
Q

How does neutralization occur by antibodies?

A

Antibodies prevent the virus/ toxin/ bacteria from attaching to the specific receptor on the host cell by either blocking the virus binding, blocking the receptor, or blocking toxins binding - attaches via the Fab region of the antibody

56
Q

How do antibodies activate phagocytic cells?

A

the Fab portion of the antibody binds to the microbial antigens on the virus/ bacteria
- the binding of a microbe to a phagocyte by more than one antibody causes cross-linking of the antibody receptors on the phagocyte surface and triggers phagocytosis of the microorganism - becomes engulfed by the extending cytoplasmic projections

57
Q

What immunity to B cells control? T cells?

A

B cells -antibody mediated immunity

T cells- cell mediated immunity

58
Q

What is the T cell receptor (TCR) on the T cell analogous to compared to a B cell?

A

Comparable to an antibody

59
Q

A large number of clonally expanded B cells become what?

A

plasma- dedicated to the synthesis and secretion of antibodies

60
Q

What is one major difference between T cell and B cell clonal extension and selection?

A

T cell receptors do not undergo further selection as a result of somatic mutation

61
Q

What is the overall goal of clonal selection and expansion in BOTH B and T cells?

A

To provide memory cells

62
Q

What is the purpose of memory cells?

A

they are more readily stimulated by an antigen
- they have a greater combining power
(B cells combine through mutation and selection and T cells combine through an increased expression of accessory adhesion molecules)
** memory cells are the basis principle for vaccination

63
Q

What are the two methods of lymphocyte stimulation?

A

T independent antigens and T dependent antigens

64
Q

How do T dependent antigens work?

A

T lymphocytes can be activated by interdigitating dendritic cells (naive T cells)

  • immature IDC’s take up the antigen which is processed and presented on the surface peptide to the MHC 2
  • the IDC migrates to the T cell region of the draining lymph node, where it stimulates several T lymphocytes - binds via the TCR
  • primed T cells are more readily stimulated bu the
65
Q

What are the 2 types of T-independent antigens?

A
  • polyclonal activators - stimulate a wide variety of B cells independently of their specific antigen receptors
  • repeating determinants - give rise to low-addinity IgM rather than IgG Ab response and do not induce memory response
66
Q

Most antigens stimulate B cells only if assisted with what? How does this work?

A

Only assisted helper T -lymphocytes

  • antigen binds to Th and presents the antigen on the B cell surface
  • this results in cytosine production to activate B cells which undergo clonal expansion
67
Q

What are cytokines?

A
  • soluble intracellular communication factors - hormones of the immune system
  • these are non-antigen specific molecules
  • have a diverse activity
  • are important to protect against infectious diseases, contribute to the control of infection and contribute to the development of pathology
68
Q

The production of cytokines helps define T-heler subsets how?

A
  • there are mutual antagonism between two subsets of Th cells
  • – IL-4 down regulates Th1 cells
  • – IFNgamma suppresses the activity of Th2 lymphocytes
69
Q

IFNgamma activates what?

A

activates macrophages

70
Q

IL-4 and IL-5 activate what?

A

B cells, mast cells and eosinophils

Microbiology (16 decks)

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