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MICR 270 > Module 3 > Flashcards

Module 3 Flashcards

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1
Q

5 phases of adaptive immune response

A
  1. Antigen recognition
  2. Lymphocyte activation
  3. Eliminations of pathogens
  4. Contraction
  5. Memory
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2
Q

Antigen recognition

A

-after pathogen has entered body and and evaded innate immune defences, PAMPs are seen by antigen-presenting cells (APCs)
-APCs will present antigens to naive T-cells via their surface MHC proteins

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3
Q

Lymphocyte Activation

A

-requires a series of cellular interactions which lead to T-cell and B-cell differentiation and clonal expansion

Bcells -> plasmocytes
Tcells -> Cytotoxic T-cells

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4
Q

Eliminations of Pathogens

A

-depending on type of pathogen invading, most efficent defenses are unleashed: Hummoral or Cell-mediated

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5
Q

colonal Expansion

A

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

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6
Q

Hummoral elimination of pathogens

A

plasmocytes produce antibodies that bind to extracellular pathogens

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7
Q

cell-mediated elimination of pathogens

A

cytotoxic t cells destory cells infected by intracellular pathogens or get activated by antigens presented by APCs

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8
Q

contraction (apoptosis of immune cells)

A

Once the pathogen is eliminated, the vast majority of activated lymphocytes undergo apoptosis and the immune response gradually declines

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9
Q

apoptosis

A

programmed cell death that occurs in a way controlled by the cell itself, which generate alsmost no damage to surrounding area

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10
Q

establishment of immunological memory

A

the few immune cells that survive the contraction phase differentiate into memory cells

When re-exposed to the same antigen, these memory cells proliferate quickly to generate an immune response much faster and more robust

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11
Q

which processes are induced in lymphocytes during their activation?

A

differentiation and clonal expansion

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12
Q

the role of MHC molecules

A

-helps identify and recognize self from non-self molecules to ensure IS does not attack the host
-display antigenic peptides on the surface of cells
-this can be recognized by TCR and co-receptors (CD4 or CD8) to initiate an adaptive imune response, which leads to elimination of foreign antigens

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13
Q

Classification of MHC molecules

A

MHC class I and MHC class II

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14
Q

MHC class I

A

CD8 cytotoxic cell

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15
Q

MHC class II

A

CD4 helper T cell

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16
Q

hoew do T cells recognize pathogens

A

cannot recognize extracellular pathogens by themselves they require an intermediate to present them

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17
Q

how do APCs internalize pathogens

A

phagocytosis OR receptor-mediated endocytosis and process them into peptides (antigens) and displayed on the MHC on the surface and are recognized by T cells

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18
Q

Receptor-mediated endocytosis

A

an endocytic process in which a cell absorbs external material by invagination of the plasma membrane. This process relies on receptors specific for the material being absorbed

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19
Q

two types of APCs

A

professional and nonprofessional

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20
Q

Professional APCs

A

MACROPHAGE, B CELL & DENDRITIC CELL

most efficent cells that both present antigens through MHC class II and express cosimulatory signals to activate helper T cells

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21
Q

nonprofessional APCs

A

other cell types can be inducedto express MHC class II complexes or stimulatory molecules, but normally they dont. This isbecause these cells will rarely be needed in this specific function and only for short periods of time in case of sustained inflammatory response

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22
Q

examples of nonprofessional APCs

A

fibroblasts and glial cells

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23
Q

the two pathways that lead to the formation of surface cell complexes

A

endogeneous and exogeneous

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24
Q

endogenous pathway

A

forms peptide MHC class I recognized by CD8 cytotoxic T cells

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25
exogenous pathway
form peptide MHC class II recognized by CD4 helper t cells
26
Antigen processing by the endogenous pathway
-allows cell to proccess self or foreign intracellular particles and present them at the cell surface in order to be recognized by T cell receptors of cytotixic T cells
27
Why would cells need to present intracellular particles to the immune system
degrading self or foreign elements into peptide fragments which are transported to ER to associate with MHC class I. this complex is transported to golgi complex, further processed and transported to surface
28
5 main steps in the process of exogenous antigen presenting
1. Antigen engulfment 2. proteolytic processing 3. Formation of MHC-antigen complex 4. cell surface expression 5. recognition by helper T cell
29
Exogenous: Antigen engulfment
antigen presenting cells engulf the foreign antigen by endocytosis forming and endosome. The antigen is generally recognized by PRRs
30
Exogenous: Proteolytic processing
Foreign antigens inside the endosome are broken down into fragments by proteolytic processing
31
what is proteolytic processing
protease cleaves one or more bonds in a target protein to modify its activity (activation, inhibition or destruction of activity)
32
Exogenous: formation of MHC-antigen complex
the vesicle containing the foreign fragments fuses with vesicles containing MHC molecules (originating from the endoplasmic retitculum via the golgi) forming MHC-antigen complexes
33
exogenous: cell surface expression
the MHC-antigen complex is transported to the plasma membrane, where it will be displayed on the surface of the cell
34
exogenous: recognition by helper T cell
the t cell receptor (TCR) on teh surface of a helper t cell binds to the MHC-antigen complex on the cell surface of the APC, which will initiate an adaptive immune response
35
B-cell Receptor (BCR)
the BCR is composed of a membrane-bound antibody and signal transduction molecules (ITAMs). BCRs recognize and bind to extracellular pathogens or toxins directly
36
ITAMs
an immunoreceptor tyrosine-based activation motif is composed of a repeated sequence of four amino acids in the cytoplasmic tails of cell surface proteins
37
T cell receptor (TCR)
-TCR complex is formed of a membrane bound antigen-specific molecule and signal transduction molecules -TCRs in association with a co-receptor (CD4 or CD8) recognize and bind ti peptide MHC complex
38
CD4 co receptors are expressed on _________ cells, which recognie peptide MHC class ___________
Helper T cells, MHC class II
39
CD8 co receptors are expressed on _________ cells, which recognie peptide MHC class ___________
cytotoxic T cells, MHC class I
40
Lymphocyte Activation
involves many interactions with other immune cells, which will mediate the efficency of the specific immune response
41
cells involved in lymphocyte activation
macrophage, dendritic cell, b cell, helper t cell, cytotoxic t cell
42
cytokine networks
coordinate appropriate immune responses and modulate the balance between humoral and cell-mediated immunity
43
classes of cytokines depdndent on function and structure:
-chemokines -interleukins -interferons -tumor necrosis factor -growth factors
44
what does the immune system require to stimulate hummoral immunity and differentiation of B cells
CD4 helper T cells
45
two categories of antigens acle to activate B cells
thymus-dependent and thymus-independent
46
thymus-independent antigens
few antigens that can induce the production of antibodies by B-cells without the presence of a T-cell
47
T-cell dependent B cell activation
involves specific signals essential to the productionof functional plasmocytes and memory B-cells. This interaction induces an exchange of singals between 2 lymphocytes allowing activation of hummoral response
48
steps leading to signals in the process of B cell activation
1. Peptide-MHC class II complex 2. Signal 1: TCR- peptide:MHC complex 3. expression of cosimulatory molecules 4. Signal 2: Cosimulation 5. Signal 3: Cytokines 6. outcome of three signals
49
how many signals lead to b cell activation and what are they
1. TCR-peptide:MHC complex Class II 2. Cosimulation 3. Cytokines
50
Step 1 of b cell activation
peptide-MHC class II complex as the antigen binds BCR on a specific B cell does not produce a strong enough signal to activate the cell, the antigen is internalized by receptor-mediated endocytosis, processed and displayed on the cell membrane as MHC
51
At what stage does the B cell acting on APC express a high level of peptide: MHC complex on their cell surface
step 1
52
Step 2 b cell activation
Signal 1: TCR-peptide: MHC complex the specific TCR complex and CD4 co-receptor on the T cell recognizes and binds to peptide: MHC complex on B cell
53
Step 3 b cell activation
expression of cosimulatory molecules Signal 1 induces the expression of CD40L on the cell surface of the helper T-cell
54
Step 4 B cell activation
Signal 2: Co-stimulation CD40L and CD28 expressed on the T-cell, respectively, bind to CD40 and B7 expressed on the V-cell inducing a costimulatory signal in both cells
55
The immune synapse structure
t-cells will not become properly activated if only signal molecules such a t-cell receptor and a peptide:MHC complex interaction. a immune synapse consisting of signal molecules AND adhesion proteins must be formed
56
what is an immune synapse
interaction between a t-cell and a APC
57
three components of an immune synapse
1. Signal molecules (cSMAC) 2. Adhesion molecules (pSMAC) 3. signal regulation molecules (dSMAC)
58
signal molecules (cSMAC) in immune synapse
the central SMAC contians the molecules responsible for signalling between the two cells such as the TCR and peptie:MHC molecules
59
adhesion molecules (pSMAC) in immune synapse
the peripheral SMAC contains adhesion proteins, auch as integrins and cytoskeletal linker proteins, responsible for keeping the cells in contact long enough for signals to propogate
60
signal regulation molecules (dSMAC) in immune synapse
the distal SMAC consists of proteins with large extracellular domains that are responsible for helping regulate signal transduction
61
pattern of immune synapse
"bullseye" with three rings depicting three different cell clusters (SMAC). other immune synapses can be arranged differently
62
Function of Immune Synapse
Primary goal: effective activaton of the T cell - holds signal proteins together to form stronger connections, giving enough time for right amount of signals -reorganization structures inside the t cell, directing the release of cytokines close to target cell -regulates lymphocyte activation
63
Chemokines
-induce chemotaxis -call in cells to the region of infection -play a key role in inflammation, cell mediated and hummoral responses and hematopoiesis
64
Interleukins
-contain over 10 subfamilies -regulate immune and inflammatory responses -primarily affect the proliferation and differentiation of various hematopoietic and immune cells
65
Interferons
-the most common and well-known interferon molecules are IFN-apla and IFN-y -induce antiviral state - inhibit the replication process of virsus - helps regulate immune responses
66
Tumor Necrosis Factor
-most common are TNF-alpha and TNF-beta -involved in systemic inflammation (septic shock) -involved in tumor regression -can cause apoptosis (cell death)
67
Growth Factors
-stimulate: growth, proliferaition, healing, cellular differentiation -regulate a variety of cellular processes such as immune responses
68
what is the outcome of B cell activation:
proliferation and differentiation into plasma and memory B cells
69
what is imunological memory
the ability of lymphocytes to respond more efficently to re-infection by a previously encountered antigen
70
when does immunological memory occur
when there is a second encounter with an antigen that induces a hightened state of immune reactivity, mediated by memory B cells
71
why do we get the flu multiple times if memory cells last for decades
due to different strains
72
memory B cells vs naive B cells
memory B cells differentiate from naive B cells and display the same membrane-bound antibody as parent cell *memory b cells have longer
73
how do memory b cells work fast than naive b cells
naive b cells need to be activated through series of cell interactions (like antigen presentation) before they can differentiate into plasma cells and memory cells. memory cells can differentiate immediately into plasma cells making them faster
74
Natural Passive Immunity
-acquired by the fetus or newborn from the mother -placental transfer of antibodies during pregnancy or breastfeeding -short lived (6 months) -no immunological memory for reciepent
75
Artificial passive immunity
-acquired by injection of serum containing antibodies -immunity is temporary -no immunological memory for reciepnt
76
Natural active immunity
-acquired through infection by a pathogen possibly leading to symptoms -development of innate and adaptive immune responses -immunological memory has significant change of being developed
77
Artificial Active Immunity
-acquired through vaccination -development of innate and adaptive immune responses -normally no symptoms -imunological memory has significant chnage of edveloping

MICR 270 (5 decks)

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