Immune response against microbes

Question 1

General features of immune responses to microbes

Answer 1

responses always involve innate and adpative immunity

the immune system responds in distinct and specialized ways to different types of microbes to be most effective

microbes evade or resist the effector mechanisms of immunity

many microbes establish latent, or presistent, infections. The immuner esponse controls but does not eliminate the microbe and the microbe survives without propagating the infection

in many infections, tissue injury and disease may be caused by the host response rather than by the microbe itself

Question 2

First line of defnse

Answer 2

mechanical barrier

secretions

commensal bacteria

low pH

physical mechanisms

Question 3

second line of defnse

Answer 3

innate immunty: nonsepcific, macrophages, neutrophils, complement

adaptive immunty: antigen specific, lymphocytes (B and T cells) antibodies

Question 4

Extracellular bacteria

Answer 4

extracellular bacteria may either induce inflammation or produce toxins

they are ony capable of replicating and surviving outside of host cells

Innate response, adaptive repsonses, bacterial toxins, evasion of immune responses, overreaction of immune response

Question 5

Bacterial toxins

Answer 5

exotoxins: secreted by bacteria. neutralized by IgG and IgA
endotoxins: not secreted. LPS of cell wall

Question 6

Extracellular bacteria evasion of immune response

Answer 6

bacterial capsules: external polysaccharide structure. prevent desiccation and resist phagocytosis

biofilms: prevents phagocytosis. increase tolerance to antibiotics. Pseudomonas

Question 7

Extracellular bacteria evasion of immune system

Answer 7

antigenic variation

complement inhibtion

neutralization of reactive : catalase producing bacteria

protein A (staph) and protein G (strep): bind antibody and block opsonization and phagocytosis

Question 8

overreaction to extracellular bacteria

Answer 8

abscess: collection of immune cells with a surrounding capsule

Septic shock

Question 9

intracellular bacteria

Answer 9

surivive and replicate in host cells

they require cell mediated immunity to be eliminated as they are not able to be seen by antibodies and complement: innate response, adaptive response, evasion of immune response, overreaction of immune response.

Question 10

Intracellular bacteria: innate immune response

Answer 10

phagocytes (DC/macrophages) become infected with intracellular bacteria

they release IL 12 which activate NK cells

NK cells then release IFN which activates phagocyte to kill the bacteria

Question 11

Intracellular bacteria: adaptive immune response

Answer 11

innate immune response often fails to control intracellular infections

t cell mediate immunity is the primary protective response

CD4 cells (TH1) release IFN (activates phagocytes to kill bacteria)

TH1 cells have CD40L which activates phagocyte via CD40

CD8 cells kill infected cells

Question 12

phagocyte activation

Answer 12

following IFN stimulation of infected phagocyte, microbes are eliminated by the fusion of hte phagosome and lysosome and exposure to reactive nitrogen intermediates (RNI) and reactive oxygen intermediates (ROI)

Question 13

Intracellular bacteria evasion of immune system

Answer 13

escape from phagosomes

inhibition of phagosome and lysosome fusion

detoxification of RNI and ROI (catalse neutralized h202)

diminish phagosome’s ability to present antigens to CD4 T cells

Question 14

overreaction to intracellular bacteria

Answer 14

granulom: collection of immune cells. Tuberculosis

promotes survival of bateria

Question 15

Viruses

Answer 15

survive and replicate inside host cells

they require cell mediated immunity to be eliminated as they are not able to be seen by antibodies and complement

Question 16

Viruses: innate immune response

Answer 16

host cell pattern recognition receptors (PRR) recognize viral pathogen associated molecular pattern (PAMPS)

infected cell produces cytokines (IFN a and B) which elicit antiviral properties in neighboring cells

NK cells recognize loss of MHC and kill infected cell

Question 17

Virus: adaptive immune response

Answer 17

humoral response is effective when virus in outside of host cells

antibodies can neutralize virus and prevent its entry into cells

Question 18

Viral evasion: antigenic drift vs shift

Answer 18

antigenic shift vs drift. anitgenic drift creates influenza viruses with slightly modified antigens, while antigenic shift generate viruses with entirely new antigens

Question 19

viral evasion of immune system

Answer 19

code for anitbody receptors to block effector anitbody functions

inhibit IFN synthesis

produce soluble IFN receptors to block IFN function

mimic MHC molecuels, thus avoid being killed by NK cells (remember that NK cells kill cells that lack MHC)

Inhibit MHC I molecule expression, thus avoid CD8 cell recognition

decreases production of IL 12 (IL 12 stimulates IFN production by NK)

T cells and increases cytotoxic acitivity

viral latency EBV and herpes

Question 20

Overreaction to virus: cirrhosis in hep B

Answer 20

HBV is not directly toxic to hepatocytes and people with imparied cellular immunity will have no inflammation

hepatocytes adre damaged by the immunological response

if the infection is not cleared, the insufficient immune response will continue and cause progressive liver damage.

Question 21

Fungi

Answer 21

Can occur as yeast or mold (hypae)

Question 22

Fungi: innate immune response

Answer 22

antibdoy opsonization

neutrophil and macrophage phagocytosis of yeast

pattern recognition receptors recognize pathogen associated molecules patterns

release of proinflammatory cytokines (IL12). Phagosome and lysosome fusion

neutrophils release NETS (neutrophil exracellular traps) for hyphae

Question 23

Fungi adaptive immune response

Answer 23

T helper subsets are important

TH1 cells secrete IFN gamma and promote fungal clearance

TH17 cells recruits neutrophils

TH2 cells inhibit fungal clearance and have a role in allergic disease

T helper cell importance is seen in AIDS, where a lack of CD4 helper cells leads to increase susceptibility to fungal infections

Question 24

Fungi evasion of immune response

Answer 24

stimulate production of Il 10 (inhibitory cytokine)

inhibit IL-12

inhibit phagolysosome

change cell wall composition: changing surface glycoproteins

Question 25

Overreaction of fungi

Answer 25

granulomas

Question 26

parasites

Answer 26

protozoa (one cell organisms)

helminths (multicellular worm)

Question 27

parassite innate immune response

Answer 27

PRRS recognize PAMPs mobilizes and activates macrophages

antigen presentation and activation of adaptive immune system

rarely eliminates parasites, just slows the growth

Question 28

parasites: adaptive immune response

Answer 28

antibodies neutralize the extracellular protozoa

CD8 t cells can kill infected cells directly

TH1 serete IFN and activate macrophages to kill intracellular protozoa

th2 cells are the primary response to helminth infections

Question 29

Parasites adaptive imune response

Answer 29

IL13: cell turnover mucus

IL5: recruit eosinophils

IgE: regulates mast cells and enhance elimination

mast cells: inflammatory response. Mucus production. Muscle contraction.

Question 30

Parasite evasion of immune system

Answer 30

antigenic variation

stage specific: different antigens see at different stages in the life cycle. COntinual alteration of antigens with replication

production of IL 10

prevention of lysosome and phagosome fusion

produce antioxidants to neutralize lysosome effects

Question 31

overreaction to parasites

Answer 31

hepatosplenomeagly

increase in size and number of macrophages and engorgement of blood vessels