immune response to infectious agents Flashcards

1
Q

innate vs adaptive immunity

A

in innate, thereis inhibition of infection by type 1 interferons and killing of infected cells by NK cells

in adaptive, there is killing of infected cells by CD8 CTLs(cytotoxic t lymphocytes) and neutralizing antibodies block virus binding and entry to host cells.

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2
Q

PAMPs

A

(pathogen associated molecular patterns) are microbe molecules that are recognized by TLRs the innate immune system (toll like receptors) and PRRs(pattern recognition receptors)
o PAMPs activate type 1 interferons (IFN-alpha and IFN-beta)

 Viral PAMPs = ssRNA, dsRNA, and uncapped RNA

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3
Q

PRRs

A

pattern recognition receptors

receptors on host cells that recognize viral PAMPs

TLRs 3, 7, and 8

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4
Q

how do type 1 interferons work in innate immune response?

A

PAMPs activate type 1 interferons (IFN-alpha and IFN-beta)
 Viral PAMPs = ssRNA, dsRNA, and uncapped RNA

Type 1 interferons then:
 Induce enzymes that inhibit viral replication
 Increase expression of ligands for receptors on NK cells
 Activate NK cells to proliferate and kill virus-infected cells (apoptosis)

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5
Q

how do NK cells function in innate immune response?

A

type 1 interferon causes differentiation of cytotoxic NK cells (they kill infected cells by inducing apoptosis)

o	Healthy cells express MHC1 which connects with NK cell inhibitory receptor(no apoptosis)
o	Virus-infected cells do not express MHC class 1 (inhibited by virus)  connects with the NK cell activating receptor

NK cell killing is done via
 Perforin and granzymes = granzymes enter through perforin holes  activation of caspases and apoptosis of cell

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6
Q

which immune response uses NK cells?

what do NK cells use to kill?

A

innate

NK cell killing is done via
 Perforin and granzymes = granzymes enter through perforin holes  activation of caspases and apoptosis of cell

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7
Q

innate immune system response to viruses vs intracellular organisms vs extracellular organisms

A

viruses –> type 1 IFN and NK cells

intra –> phagocytes and NK cells

extra –> complement and phagocytes

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8
Q

adaptive immune system response to viruses vs intracellular organisms vs extracellular organisms

A

viruses –> CD8 (CTLs) and B cells/CD4

intra –> CD8 and CD4(TH1)

extra –> B cells/Ig and CD4

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9
Q

what activates NK cells?

A

TYPE 1 interferons

IFNalpha, IFNbeta, TNFalpha, and IL12

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10
Q

CTLs

A

cytolytic (cytotoxic) T lymphocytes (CTLs) = CD8+ T cells

part of adaptive immunity

CTLs can kill using
 Perforin and granzymes
Or
 FasL (Fas ligand) – Fas receptor is on the virus-infected cell  Fas + FasL induces apoptosis

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11
Q

how do CTLs sense virus?

A

o Viral proteins are presented on MHC class 1 to TCR on CD8+ Tcells

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12
Q

do CTLs affect healthy normal cells?

A

no, target specific

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13
Q

Thelper and neutralizing antibodies in adaptive immunity

A

Neutralizing antibodies block virus binding and entry into host cells – virus cant bind to host cell receptors!
o CD4+ T helper cells also needed for immunity; IgG aids in neutralization, opsonization, and sensitization for NK killing, mast cells, and complement system

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14
Q

common intracellular pathogens

A

Mycobacterium tuberculosis
M. leprae
Listeria monocytogenes
Leishmania spp.

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15
Q

what causes the damage with intracellular pathogens?

A

host response!

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16
Q

3 components of innate immunity to intracellular pathogens

A

Phagocytes (neutrophils and macrophages)
NK cells
cytokines (IL-12 and IFN-gamma)

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17
Q

once PRR is bound, 2 things happen…

A

o Phagocytosis and Cytokine production

18
Q

phagolysosome mechanism for killing

A

Macrophage receptors that recognize microbial surface (PRRs on the macrophage) bind microbes

microbes are internalized by receptor-mediated endocytosis

fusion of the endosome with a lysosome forms a phagolysosome which degrades the microbe

19
Q

cytokine feedback loop

A

Activated macrophages secrete cytokines that stimulate NK cells

NK cell and macrophage form a synapse in which IL-12 and IL-15 activate the NK cell

NK cells proliferate and differentiate into effector NK cells that secrete IFN-gamma

IFN-gamma binds to its receptor on macrophages and activates them to increase phagocytosis and secretion of inflammatory cytokines

20
Q

adaptive immunity to intracellular bacteria consists of 3 components

A

T cells (TH1/TH2/CD40L)
IFN-gamma
macrophages

21
Q

TH1 (CD4) vs Nk cells

A

• CD4+ T cells that develop into TH1 effectors = are more effective producers of IFN-gamma; they take over from NK cells

22
Q

development of TH1 response in adaptive immunity

A

Naïve CD4+ T cell is activated by dendritic cell with co-stimulation by CD28 + B7

clonal expansion and differentiation into TH1 and TH2 effector cells + production of IFN-gamma, IL-4, and IL-5

The antigen presenting cell (dendritic or macrophage) produces IL-12 when its receptors for microbe products are activated

the IL-12 activated naïve CD4+ T cell and causes differentiation of TH1 effector cells

TH1 then produce IFN-gamma

activation of macrophages  microbes killed

23
Q

damage in etracellular pathogen immune response

A

due to their exo and endo toxins

24
Q

3 pathways of complement activation

order of activation?

A

classical
lectin pathway
alternative pathway

A –> L –> C

25
complement activation
C3 is cleaved to C3a and C3b -->cleavage exposes thioester bond  binds to pathogen surface
26
C3
o C3 is the most important complement protein! highly concentrated in body, highly reactive thioester bond, and mediates binding to pathogen surface
27
classical vs lectin vs alternative complement pathways
Classical - c reactive protein or Ab binds to specific antigen on pathogen surface alternative - pathogen surface is condusive to complement activation lectin - mannose binding lectin binds to pathogen surface
28
what does complement do after bound to pathogen?
o Opsonization and phagocytosis  C3b binds to microbe and attracts phagocyte  causes phagocytosis o Stimulation of inflammatory reactions = C3a and C5a (from C5 proteolysis) recruit and activate leukocytes  leukocytes destruct microbes o Complement mediated cytolysis = C3b binds and activates late components of complement  forms a MAC (membrane attack complex)  osmotic lysis of microbe
29
how does IL1, IL6, and TNFalpha decreased pathogen replication?
fever!, phagocytosis, and complement activation
30
what is required for both intracellular and extracellular immunity?
CD4 Th2 cells
31
how B cells and antibody act in adaptive immunity to extracellular pathogens?
Antibody mediated opsonization Opsonization of microbe by IgG binding of opsonized microbes to phagocyte Fc receptors (Fc-gamma-RI) Fc receptor signals activate phagocyte --> phagocytosis and killing ingested microbe
32
Fc receptor (FcgammaRI)
on phagocytes | binds opsonized microbes which activates the phagocyte to ingest and kill microbe
33
in the classical pathway of complement, _____ activates _____
antibody activates complement
34
early classical complement pathway? late classical complement pathway?
early = c3 --> c3a (inflammation) and c3b deposits on microbe to cause opsonization and phagocytosis late = c5 --> c5a (inflammation) and formation of MAC --> lysis
35
in extracellular pathogen adaptive immunity, ____ blocks the binding of toxin to cell receptors
antibody
36
______ responses protect against worm/helminth infections how?
Th2 TH2 cells produce IL4, IL10, IL5 --> IgE and IgG production --> mast cell degranulation and eosinophil activation
37
eosinophil granules protect against helminths because they have 3 toxic components
eosinophil peroxidase major basic protein eosinophilic cationic protein
38
eosinophil peroxidase
enzyme that poisons parasites and cells by catalyzing halogenation --> triggers histamine release from mast cells
39
major basic protein
a toxic protein that poisons parasites and cells by triggering histamine release from mast cells
40
eosinophil cationic protein
a toxic protein that poisons parasites; a neurotoxin