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MICR270 > Module 3 > Flashcards

Module 3 Flashcards

1
Q

What is the overall immune response?

A

From the entrance of the pathogen in the body to its elimination, consists of 2 arms; innate immunity and adaptive immunity

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2
Q

What are the 5 phases of adaptive immunity?

A 
1- Antigen recognition
2- Lymphocyte activation
3- Elimination of pathogens or non-self perceived antigens
4- Contraction
5- Establishment of immunological memory
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3
Q

Describe the antigen recognition phase of adaptive immunity?

A

After pathogen has entered the body and evaded innate immunity
PAMPs are seen by antigen-presenting cells
Antigens presenting cells will present said antigens to naive T-cells

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4
Q

What is the purpose of the antigen recognition phase?

A

Identify and activate the cells from adaptive immunity that are able to recognize and bind the antigens from the specific pathogen that is invading

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5
Q

Describe the lymphocyte activation phase of adaptive immunity

A

Requires a series of cellular interactions which lead to T-cell and B-cells differentiation and clonal expansion
B-cells to plasmocyte
T-cells to Helper T-cells or Cytotoxic T-cells

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6
Q

What is Clonal expansion?

A

Production of a large quantity of identical cells from the same original cell

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7
Q

What is the purpose of the lymphocyte activation phase?

A

Produce a large quantity of immune cells specific to the pathogen in order to stop the invasion

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8
Q

Describe the elimination of pathogens phase of adaptive immunity?

A

Depending on the type of pathogen invading the body, the most efficient defences are unleashed (humoral immunity or cell-mediated immunity)

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9
Q

What is the purpose of the elimination of pathogen phase?

A

Completely destroy the pathogen that has invaded the body

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10
Q

Describe the contraction phase of adaptive immunity

A

Once pathogen is eliminated.

Vast majority of activated lymphocytes undergo apoptosis and the immune response gradually declines

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11
Q

What is the purpose of the contraction phase?

A

Adaptive immune cells are not needed anymore and could actually produce more damage than good, thus must die

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12
Q

Describe the memory phase of adaptive immunity

A

The few adaptive cells that survive the contraction phase differentiate into memory cells
- When re-exposed to same antigen, these cells proliferate quickly to generate a much faster and much robust immune response

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13
Q

What is the goal of vaccination?

A

To generate immunological memory. It induces the production of memory cells without developing major symptoms

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14
Q

Why does adaptive immunity need a process called antigen recognition?

A

Necessary to identify which cell(s) should be activated (out of the countless number of adaptive cells) to encounter the specific invader during an infection

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15
Q

Which processes are induced in lymphocytes during their activation?

A

Differentiation and clonal expansion

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16
Q

At which step of the adaptive immune response is it determined if the type of immunity induced is humoral or cell-mediated?

A

Actually, immune responses are mounted in a non-specific fashion. Host mounts both humoral and cell-mediated response to clear the pathogen and hopefully one of these prongs of attack is effective. Finding out which response correlates to better protection is what allows us to design specific therapies against a specific pathogen

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17
Q

Why do immune cells die after the elimination of the pathogen

A

Vast majority of cells are no longer needed. If they stay alive, they consume unnecessary energy that could be better used and there is a risk that these extra immune cells could cause additional non-specific damage

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18
Q

What are the advantages of having memory cells?

A

Memory cells can last for a very long time in the body and will respond much faster and stronger in case of reinfection with the pathogen

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19
Q

What is the role of the major histocompatibility complex (MHC) ?

A

Molecules that display antigenic peptides on the surface of cells. The MHC-antigen complex can be recognized by the T-Cell receptor and its co-receptors (CD4 or CD8) to initiate an adaptive immune response, which leads to elimination

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20
Q

Which class of Major Histocompatibility Complex (MHC), do CD8 cells recognize?

A

Class I

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21
Q

Which class of Major Histocompatibility Complex (MHC), do CD4 cells recognize?

A

Class II

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22
Q

What is the basis of autoimmune disorder?

A

When the body’s immune response is unable to differentiate between self and non-self and immune system begins to attack its own tissue

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23
Q

Why are helper APCs essential in the process to induce an effective adaptive immune response&?

A

T-cells are not able to recognize extracellular pathogens by themselves, they require and intermediate to present them the antigens found inside the body. (Antigen-presenting cells, APCs)

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24
Q

What are the 2 types of antigen presenting cells?

A

Professional APCs and Non-Professional APCs

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25
Q

What do Antigen-Presenting Cells (APCs) do?

A

Internalize pathogens, by phagocytosis or receptor-mediated endocytosis, and process them into peptides (also called antigens). Antigens are then displayed on the MHC complex on the surface of the APC and can be recognized by T-cells

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26
Q

Which cells are Professional APCs? (3)

A

1- Macrophage
2- B-cell
3- Dendritic Cell
Most efficient cells that both present antigens through MHC class I and express costimulatory signals to activate helper T-cells

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27
Q

Which cells are non-Professional APCs? (2)

A

1- Fibroblasts
2- Glial Cells
Can be induced to express MHC Class II complexes over stimulatory molecules, but normally they don’t, bc they rarely are needed in this specific function.

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28
Q

What are the 2 pathways leading to the formation of the MHC signalling complexes?

A

Endogenous pathway

Exogenous Pathway

29
Q

What type of MHC signalling complex does the endogenous pathway form?

A

MHC class I complex

30
Q

What type of MHC signalling complex does the exogenous pathway form?

A

MHC class II complex

31
Q

Describe the endogenous pathway

A

Process begins by degrading self or foreign elements into peptide fragments which are transported into the ER to associate with MHC class 1. This complex is transported to the Golgi complex, further processed and transported to the cell surface as peptide: MHC class I complex for recognition

32
Q

What are the 5 main steps of the exogenous pathway

A

1- Antigen engulfment: by endocytosis forming an endosome, antigen generally recognized by PRRs
2- Proteolytic processing: in endosome, antigen are broken down into fragments
3- Formation of MHC-antigen Complex: vesicle containing the foreign fragments duses with vesicles containing MHC molecules - forming MHC-antigen complexes
4- Cell Surface Expression: MHC-antigen complex is transported to the plasma membrane, where it will be displayed on surface of cell
5- Recognition by helper T-cell: TCR on the surface of a helper T-cell bind to the MHC antigen complex on the cell surface of the APC

33
Q

Describe the BCR (2 characteristics)

A
  • Composed of a membrane-bound antibody and signal transduction molecules (ITAMs)
  • BCRs recognize and bind to extracellular pathogens or toxins directly
34
Q

Describe the TCR (2 characteristics)

A
  • TCR complex is formed of a membrane-bound antigen-specific molecule and signal transduction molecules (CD3 and ITAMs)
  • TCRs in association with a co-receptor (CD4 or CD8) recognize and bind to peptide: MHC complex
35
Q

Where are CD4 co-receptors expressed?

A

Helper T-cells

36
Q

What do CD4 co-receptors recognize?

A

MHC class II complex

37
Q

Where are CD8 co-receptors expressed?

A

Cytotoxic T-cells

38
Q

What do CD8 co-receptors recognize?

A

MHC class I complex

39
Q

How do the components of the immune system communicate between themselves?

A
  • specific cell surface receptors found on immune cells

- well-developed cytokine network

40
Q

What are the 5 classes of Cytokine?

A 
Chemokines
Interleukins
Interferons
Tumor Necrosis Factor
Growth Factor
41
Q

Describe T-cell dependent B-cell activation?

A

CD4+ Helper T-cells stimulate humoral immunity and B-cells differentiation into functional plasmocytes

42
Q

What are the 2 ways B-cell can be activated

A

Thymus-dependent: CD4 helper T-cells (majority)

Thymus-independent: antigens induce production of antibodies by B-cells directly

43
Q

What are the 3 important signals in the process of activation

A

Signal 1:
expression of CD40L on the cell surface of the helper T-cell
Signal 2:
CD40L and CD28 expressed on the T-cell, respectively bind to CD40 and B7 expressed on the B-cell
Signal 3
Activated CD4 T-cell secretes cytokines which will bind to their associated cytokine receptor located on both cells (paracrine and autocrine effect)

44
Q

What are the 6 steps of B-cell Activation by T-cell

A

1- Peptide-MHC class II complex: antigen does not produce a strong enough signal and so it is internalized and re-displayed as MHC
2- TCR of CD4 recognizes and binds to the peptide:MHC class II complex
3- Signal 1: expression of co-stimulatory molecules on surface of helper T-cell
4- Signal 2: CD40L and CD28 expressed on T-cell bind, respectively, CD40 and B7 on the B-cell, inducing a costimulatory signal in both cells
5- Signal 3: Activated helper T-cells secrestes cytokine which will bind to their associated cytokine receptor on both cells (paracrine and autocrine effect)
6- Outcome: Stimulate proliferation and differentiation of B-cells into plasma cells and memory B-cells, forming the humoral immune response against the specific antigen

45
Q

What is the immune synapse made of? (3)

A

Signal molecules (cSMAC) - central SMAC, responsible for signaling between the 2 cells
Adhesions proteins (pSMAC)-
peripheral SMAC, responsible for keeping the cells in contact
Signal Regulation Molecules (dSMAC) - distal SMAC, responsible for helping regulate signal transduction

46
Q

What are SMAC?

A

Supra molecular activating clusters

47
Q

How is the immune synapse often arranged?

A

Bullseye pattern with 3 rings

48
Q

What are the 4 functions of the immune synapse?

A
  • Primary goal is the activation of the T-cell
  • Holds signal proteins together to form stronger connections + give enough time for right amount of signals to be produced
  • Leads to the reorganization or structure inside the T-cell, directing the release of cytokines close to target cell
  • Regulates lymphocyte activation
49
Q

What are the 3 functions of chemokines?

A
  • Induce chemotaxis
  • Call in cells to the region of infection or injury
  • Play a key role in inflammation/wound healing, cell-mediated and humoral immunities, hematopoiesis
50
Q

What is chemotaxis?

A

Movement of an immune cell in direction of an elevated concentration of chemoattractant molecule such as chemokines

51
Q

What are the 2 functions of interleukins (IL)?

A
  • Regulate immune and inflammatory responses

- Primarily affect the proliferation and differentiation of various hematopoietic and immune cells

52
Q

What are the 2 functions of Interferons (IFN)?

A
  • Induce an antiviral state- inhibit the replication process of viruses
  • Help regulate immune responses
53
Q

What are the 3 functions of Tumor Necrosis Factor (TNF)

A
  • Involved in systemic inflammation (septic shock)
  • Involved in tumor regression
  • Can cause apoptosis
54
Q

What 2 functions of Growth Factors?

A
  • Stimulate growth, proliferation, healing, and cellular differentiation
  • Regulate a variety of cellular processes such as immune responses
55
Q

Describe memory cells

A
  • Differentiate from naive B-cells
  • Display the same membrane-bound antibody as parent cell
  • longer life span than naive B-cells
56
Q

Why are memory cells faster to respond?

A

Can differentiate immediately into effector cells instead of having to be activated by a series of cell interactions like naive B-cells

57
Q

What is the most efficient long-term protection known against pathogen?

A

Immunological memory

58
Q

Describe natural passive immunity (4)

A
  • Acquired by the fetus of newborn from the mother
  • Placental transfer of antibodies during pregnancy or breastfeeding
  • Short-lived immunity (6months)
  • No immunological memory for the recipient
59
Q

Describe Artificial passive immunity (3)

A
  • Acquired by injection of serum containing antibodies
  • Immunity is temporary
  • No immunological memory for the recipient
60
Q

Describe natural active immunity(3)

A
  • Acquired through infection by a pathogen, possibly leading to symptoms/disease state
  • Development of innate and adaptive immune responses
  • Immunological memory has a significant chance of being developed
61
Q

Describe Artificial Active Immunity (4)

A
  • Acquired through vaccination
  • Development of innate and adaptive immune responses
  • Normally, no symptoms/disease states are present
  • Immunological memory has a significant chance of being developed
62
Q

What is one of the challenges with developing new vaccines?

A

Determining what your correlate of protection is - aka what part of the immune response neutralizes the pathogen, eg: antibody, T-cell, B-cell

63
Q

What is a serological analysis?

A

Serological analysis involves the diagnostic evaluation of blood serum to test for the presence of a hot antibody response against a foreign particle/pathogen

64
Q

What is immunological memory?

A

Ability of lymphocytes to respond more efficiently to re-infection by a previously encountered antigen, and as a result, develop a greater and faster immune response than the first encounter

65
Q

What is the cause shingles?

A

After exposure to Varicella, virus remains in the nervous system in an inactive state referred to as latency. Subsequent reactivation of latent

66
Q

What are ITAMs?

A

Signal transduction molecules in the BCR

Immunoreceptor tyrosine activation motifs is composed of 4 amino acids in cytoplasmic tails of cell surface proteins

67
Q

Which SMAC is responsible for helping regulated signal transduction?

A

dSMAC

68
Q

Which SMAC is responsible for keeping the cells in contact long enough for signals to propagate?

A

pSMAC

69
Q

Which SMAC is responsible for signaling between the 2 cells?

A

cSMAC

MICR270 (5 decks)

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