9: Host Defense Flashcards
extracellular bacteria innate immunity
1 Phagocytosis
- alternative complement pathway
extracellular bacteria adaptive immunity
Humoral immunity
extracellular bacteria evasion
polysaccharide capsules
genetic variation
extracellular bacteria deleterious effects
septic shock
superantigens
disease-causing antibodies (cross-reactive antibodies and immune complexes)
intracellular bacteria innate immunity
- some killed, but adaptive required for eradication
- NKC activated by macrophage-produced IL-12 produces INFgamma to activate macrophages (circle)
intracellular bacteria adaptive immunity
DTH-like type IV reaction
- TH1 cells release IFNgamma to activate macrophages
intracellular bacteria evasion
- mycobacterium: inhibits fusion of phagosomes and lysosomes
- listeria: disrupts phagosome and escapes into cytosol
intracellular bacteria deleterious effects
granulomas
viruses innate immunity
- IFN produced by infected cell protects the surrounding cells by upregulating class I MHC and activating NK cells
- NK cells lyse early in infection (1st line of defense against virus infected cells)
viruses adaptive immunity
- humoral if antibodies are present (before inside cell) because prevents virus binding to target cell
- CTLs are main immune defense against establish virus infections
viruses evasion
- antigenic variability (via error-prone reverse transcriptase)
- antigenic alteration ( via reassortants)
- prevention of class I MHC expression
viruses deleterious effects
- CTL mediated pathologic lesions (Hep B and liver)
- molecular mimicry (cross-reaction with host tissue)
fungal innate immunity
Neutrophils
fungal adaptive immunity
TH1 mediated
parasite innate immunity
- macrophages try to phagocytize protozoa
- helminths activate alternative complement but they are resistant
parasite adaptive immunity
- worms: IgE and eosinophils during ADCC (TH2 immunity)
- Plasmodium (cause malaria): TH1 mediated CTLs
- Eggs in liver: CD4 T cells recruit macros to wall off eggs in granulomas
- Protozoa within macrophages: CD4 T cells produce IFNgamma to activate macrophages
parasite deleterious effects
- immune complexes (chronic parasite infestations)
- liver fibrosis and cirrhosis (eggs)
- lymphedema/elephantitis (filaria worms)
