Immunology of infectious disease Flashcards
what are the two main tissue destruction mechanisms of extracellular bacteria?
- induce inflammation
- toxins
what are the main immunological responders to tissue borne antigens?
lymph nodes
what compound do neutrophils release during degranulation to lower local iron concentrations?
lactoferrin
deficiencies in C5-C9 predispose to infection from what organism?
neisseria
the alternative pathway relies on what to be activated?
microbial surface
which antibody is responsible for opsonizing and enhancing phagocytosis?
IgG
which antibodies activate the classical complement pathway? what is the result?
IgM and IgG
lysis of bacteria
maternal antibodies disappear in infants after how long? what infections are infants then susceptible to?
3-6 months
n. meningitidis, s. pneumoniae, h. influenzae type B
most common immunodeficiency in the human population involves what antibody? why are they often asymptomatic?
IgA
IgM can compensate
IgA opsonize bacteria at mucosal sites via what main three mechanisms?
- aggregates bacteria to facilitate expulsion
- prevents invasion of bacteria through the mucosal epithelium
- fixes complement
what component of bacteria allows them to resist phagocytosis and may inhibit complement activation via the alternative pathway?
polysaccharide capsule
forms of evasion
- polysaccharide capsule
- variation of surface antigens
- production of IgA1 protease (neisseria, h. influenzae)
how does s. pyogenes interfere with complement activation?
produces strain-specific M proteins
how does s. pneumoniae interefere with complement activation?
produces C3 protease
how does s. typhi evade the immune system?
‘syringe’ that allows secretion of proteases across macrophage plasma membrane to inhibit the NFkB mediated signaling pathway and secretion of TNFa
what are the deleterious effects of the immune system, generally?
septic shock
superantigens
which superantigen is responsible for toxic shock syndrome? what occurs as a result?
TSST-1: large release of TNFa and IL-1
what do superantigens do?
- 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
what are the two most clinically relevant spirochete organisms?
treponema pallidum - syphilis
borrelia burgdorferi - lyme disease
what is the main innate immune response to spirochetes?
neutrophils (but weak)
what is/are the main type of immunity(ies) to combat spirochetes? what is the mechanism?
cell mediated (clearing) and adaptive (prevent further infection)
- Th1 immunity most effective in CLEARING organisms
- antibodies opsonize + protective immunity (latent syphilis)
how does borrelia evade the immune system?
- coats itself with amorphous host material - prevents phagocytosis
- evades adaptive immunity
what is the innate immune response to fungi?
neutrophils
what type of adaptive immunity is effective against fungi?
humoral AND cell mediated
most importantly - cell mediated - Th1 (CTLs, granulomas)
what is the role of adaptive immunity in parasite infections?
- 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
protozoa that survive within macrophages stimulate what type of immunity?
Th1
how do CD4+ T cells combat protozoa?
secrete IFNy to activate macrophages
what is the main immune response against plasmodium?
Th1 - CTLs against intrahepatic stage of parasite
what is the main evasion strategy for:
african trypanosomes
leishmania
trypanosomes - vary surface antigens
leishmania - suppress macrophage production of IL-12
what are the deleterious effects of the immune response in:
cerebral malaria
chronic parasite infections
schistosoma eggs
- cerebral malaria - increased TNFa
- chronic parasite infections - immune complexes (vasculitis and nephritis)
- schistosoma eggs - liver fibrosis, portal HTN, cirrhosis
what specific bacterial structures are recognized by phagocytes?
RGD sequences - arginine, glycine, aspartate
what component of DNA activates macrophages?
unmethylated CpG dinucleotide motifs
how does neisseria evade the immune system?
changing surface antigens
what is the main method of immune evasion for t. pallidum?
- lacks virulence factors
- resistant to normal host immune mechanisms
immunologically, how does the lymphedema result from filarial worm infestation?
- worms lodge in channels
- chronic Th1 response
- severe fibrosis of lymph channels
how do parasites inhibit the development of Th1 immunity to vaccine antigens?
chronic infestations induce strong Th2 immunity
