Immunology of infectious disease

Question 1

what are the two main tissue destruction mechanisms of extracellular bacteria?

Answer 1

• induce inflammation

- toxins

Question 2

what are the main immunological responders to tissue borne antigens?

Answer 2

lymph nodes

Question 3

what compound do neutrophils release during degranulation to lower local iron concentrations?

Answer 3

lactoferrin

Question 4

deficiencies in C5-C9 predispose to infection from what organism?

Answer 4

neisseria

Question 5

the alternative pathway relies on what to be activated?

Answer 5

microbial surface

Question 6

which antibody is responsible for opsonizing and enhancing phagocytosis?

Answer 6

IgG

Question 7

which antibodies activate the classical complement pathway? what is the result?

Answer 7

IgM and IgG

lysis of bacteria

Question 8

maternal antibodies disappear in infants after how long? what infections are infants then susceptible to?

Answer 8

3-6 months

n. meningitidis, s. pneumoniae, h. influenzae type B

Question 9

most common immunodeficiency in the human population involves what antibody? why are they often asymptomatic?

Answer 9

IgA

IgM can compensate

Question 10

IgA opsonize bacteria at mucosal sites via what main three mechanisms?

Answer 10

• aggregates bacteria to facilitate expulsion
• prevents invasion of bacteria through the mucosal epithelium
• fixes complement

Question 11

what component of bacteria allows them to resist phagocytosis and may inhibit complement activation via the alternative pathway?

Answer 11

polysaccharide capsule

Question 12

forms of evasion

Answer 12

• polysaccharide capsule
• variation of surface antigens
• production of IgA1 protease (neisseria, h. influenzae)

Question 13

how does s. pyogenes interfere with complement activation?

Answer 13

produces strain-specific M proteins

Question 14

how does s. pneumoniae interefere with complement activation?

Answer 14

produces C3 protease

Question 15

how does s. typhi evade the immune system?

Answer 15

‘syringe’ that allows secretion of proteases across macrophage plasma membrane to inhibit the NFkB mediated signaling pathway and secretion of TNFa

Question 16

what are the deleterious effects of the immune system, generally?

Answer 16

septic shock

superantigens

Question 17

which superantigen is responsible for toxic shock syndrome? what occurs as a result?

Answer 17

TSST-1: large release of TNFa and IL-1

Question 18

what do superantigens do?

Answer 18

• bind to MHC II proteins on APCs and to certain Vb chains on T cells - activates T cells
• septic shock like reaction due to T cells and macrophages producing TNFa

Question 19

what are the two most clinically relevant spirochete organisms?

Answer 19

treponema pallidum - syphilis

borrelia burgdorferi - lyme disease

Question 20

what is the main innate immune response to spirochetes?

Answer 20

neutrophils (but weak)

Question 21

what is/are the main type of immunity(ies) to combat spirochetes? what is the mechanism?

Answer 21

cell mediated (clearing) and adaptive (prevent further infection)

• Th1 immunity most effective in CLEARING organisms
• antibodies opsonize + protective immunity (latent syphilis)

Question 22

how does borrelia evade the immune system?

Answer 22

• coats itself with amorphous host material - prevents phagocytosis
• evades adaptive immunity

Question 23

what is the innate immune response to fungi?

Answer 23

neutrophils

Question 24

what type of adaptive immunity is effective against fungi?

Answer 24

humoral AND cell mediated

most importantly - cell mediated - Th1 (CTLs, granulomas)

Question 25

what is the role of adaptive immunity in parasite infections?

Answer 25

• IgE production (Th2 mediated response - mast cells release histamine to increase lymph flow to flush out parasites)
• Th1: CTLs, macrophages-mediated killing and/or IgG
• Th2: IgE and infiltration by eosinophils

Question 26

protozoa that survive within macrophages stimulate what type of immunity?

Answer 26

Th1

Question 27

how do CD4+ T cells combat protozoa?

Answer 27

secrete IFNy to activate macrophages

Question 28

what is the main immune response against plasmodium?

Answer 28

Th1 - CTLs against intrahepatic stage of parasite

Question 29

what is the main evasion strategy for:

african trypanosomes
leishmania

Answer 29

trypanosomes - vary surface antigens

leishmania - suppress macrophage production of IL-12

Question 30

what are the deleterious effects of the immune response in:

cerebral malaria
chronic parasite infections
schistosoma eggs

Answer 30

• cerebral malaria - increased TNFa
• chronic parasite infections - immune complexes (vasculitis and nephritis)
• schistosoma eggs - liver fibrosis, portal HTN, cirrhosis

Question 31

what specific bacterial structures are recognized by phagocytes?

Answer 31

RGD sequences - arginine, glycine, aspartate

Question 32

what component of DNA activates macrophages?

Answer 32

unmethylated CpG dinucleotide motifs

Question 33

how does neisseria evade the immune system?

Answer 33

changing surface antigens

Question 34

what is the main method of immune evasion for t. pallidum?

Answer 34

• lacks virulence factors

- resistant to normal host immune mechanisms

Question 35

immunologically, how does the lymphedema result from filarial worm infestation?

Answer 35

• worms lodge in channels
• chronic Th1 response
• severe fibrosis of lymph channels

Question 36

how do parasites inhibit the development of Th1 immunity to vaccine antigens?

Answer 36

chronic infestations induce strong Th2 immunity