Immune Response To Microbial Infections

Question 1

Host Pathogen Interactions and what decides if infection will occur

Answer 1

Transmission and entry—> Colonization—> multiplication—>invasion of host tissue—>dissemination—> damage to the host cells

Pathogen virulence factors (Host immune status)

Question 2

General features of Immune response against pathogens

Answer 2

Innate and adaptive
Distinct and specialized immune response for different microbes
Evade immune mechanisms
Latent or persistent infections

Question 3

Different Types of microbes

Answer 3

Parasites protozoa etc
Extracellular parthogens: can grow and reproduce freely and move extensively in tissues caught by antibodies complement immune cells
Intracellular Pathogens: Can live inside host cells Hide from antibodies complement etc Navigate the intracellular immune response

Question 4

Which part of the immune system provides a distinct and specialized immune responses for different types of microbes? Mediators of adaptive immune system

Answer 4

Adaptive
CD4 T cells Th1 Th2 and Th17
CD8 Tcells
Antibodies - different isotypes

Question 5

CD4 T cell

Answer 5

Th1–> IL12–> IFN g macrophages
Th2–> IL4–> IL4, IL5, IL13 eosinophil helminths
Th17–> IL1, IL6, IL23 TGFB—> IL17 IL22–> Neutrophils—> extracellular bacteria and fungi

Question 6

CD8 T cells and Antoibody Isotopes

Answer 6

Antigen recogn and conjugate formation—> CTL activation—> Granule exocytosis—> Detachment of CTL—> Target cell death

CD40 - CD40L and cytokines required for class switching

Cytokines involved IL4 —> IgE immunity against helminths type 1 hypersensitity and IgA mucosal
Mucosal tissues cytokines—> TGFB BAFF—> IgA—> mucosal immunity through breast milk
IgG Subclasses —> Opsonization complement activation neonatal immunity

Question 7

Extracellular bacteria: strep psueu, neisseria spp and staph aur

Answer 7

Capable of replicating outside host cells; replicate through blood, CT, airway, GI tract
Innate immune components: Complement and neutrophils
Adaptive immune components: Antibodies (humoral immunity) and Th17 cells

Question 8

Which Innate immune mediator may be important in killing extracellular bacteria?

Answer 8

Complement
GPB - Peptidoglycan and GNB - LPS - activate alternative pathway Mannose on bacteria surface - lectin pathway
Phagocytosis by neutrophils & macrophages
Phagocytes & complement—> cytokines—> leukocyte infiltration—> destroy bacteria

Question 9

Which adaptive immune mediator may be important in eliminating extracellular bacteria in blood

Answer 9

Antibodies mediate killing via neutralization—> opsonization and phagocytosis—> complement by classical pathway

Question 10

Evasion Mechanism of Extracellular bacteria

Answer 10

Inhibition of complement activation; sialic acid deposition on surface
Defense against antibodies; antigenic variation, IgA protease
Resistance to phagocytosis; CAPSULAR POLYSACCHARIDE strep peu & Hae infl
ROS

Question 11

Intracellular Bacteria; Innate immune cells that are involved during intracell bact infection?

Answer 11

Innate Immune response;
Macrophages—> IL12–> Th1–> NK cells
NK Cells (provides early defense) —> IFN g —> macrophages
Intracellular bacteria—> NK cells

Question 12

What Happens when Mycobacterium Tuberculosis cannot be cleared by Macrophages?

Answer 12

Granuloma Formation around foci of infection
Alveolar macrophages produce TNF a, IL12/IFN gamma
MTB components activates TNF a —> disease progression and symptoms
Th1 type response and IFNy production; increase phogolytic, phagocytic, NO, cytokine production recruit more T and NK cells

Question 13

What type of hypersensitivity do granulomas display?
Activation of NK cells

Answer 13

Type IV/delayed type hypersensitivity formed by macrophages and lymphocytes (T cells)
2 receptors:
a) Activation receptors; antibody coated cells, viral HA, lectins antigens searched for by NK cells on MHC I
B) Inhibitory Receptors; recognize MHC I on cells
MHC I expression when down-regulated by viral infections and tumor cells is marked by NK cells

Question 14

Adaptive Immune Response
Would CD8 T cells play a role during intracellular bacteria infection?
Evasion mechanism of Intracellular Bacteria
Which adaptive immune system will kill if pathogen escape into the cytoplasm

Answer 14

Th1 response
Macrophage activation—> IL12–> Th1 —> IFN y
Yes
Inhibition of phagolysosome formation; Mycobacterium tuber and legionella
Inactivate ROS; Mycobacterium leprae
Destruction of phagosome membrane, escape into cytoplasm; listeria Monocytogenes
CD8 T cells

Question 15

TB skin test develops an indurated erythematous lesion at injection site 3 days following injection of TB antigens

Answer 15

Mononuclear cell infiltration following chemokine release from memory CD4 cells

Question 16

Defense Against Viruses

Answer 16

Innate: Inhibition of infection by type 1 interferons, NK cell mediated killing of infected cells
Adaptive: CTLS; MOST IMPORTANT CELL IN RECOVERY FROM VIRAL INFECTIONS
Protection from reinfection following vaccination; neutralizing antibody

Question 17

Type 1 Interferons
CD8 T cells (cytotoxic T cells CTL)
NK Cells recognize Target cells via?

Answer 17

A) Induction of antiviral state B) Increased expression of class I MHC molecules on infected cells killing by CTLs
KILL VIRALLY INFECTED CELLS IN A CLASS I MHC RESTRICTED ANTIGEN SPECIFIC MANNER; kill via perforin/granzymes, Fas/FasL, Cytokine production, recovery for virally infected cells
KARS and KIRS regulated lytic activity—> lysis involves perforin/granzymes—> ADCC(NK cells have Fc receptors for IgG)

Question 18

Immunity to Parasites; Defense against Extracellular and intercellular (What type of response would be most beneficial for the host?)

Answer 18

*Protozoans; Intracellular and Extracellular
*Helminths; Extracellular Each stage presents new antigens to immune system
Macrophages and neutrophils—> activate complement—> Opsonize and block anti-parasite antibodies

Macrophage mediated killing with TH1 cell activation

Question 19

Leishmania

Answer 19

Th1 cell activation produces IFNg which activates the infected macrophages enabling them to clear parasites

Question 20

Immunity of Fungi

Answer 20

Extracellular: a) Opsonins; Compliment & Antibody b) Phagocytes; Neutrophils
Intracellular: Activated Macrophages requires Th1 cells to supply IFNg
Innate Immunity: Neutrophils dendritic cells—> sense fungal organism via TLRs and C type lectin receptors (dectins recognize B glutans on fungi surface)—> release cytokines —> neutrophils release ROS and lysosomal enzymes phagocytose fungi
Intracellular: CD4 T cells Th1 type IFNy activate macrophages
Can elicit granulomatous inflammation