Mechanisms of Immunity Flashcards
categories of pathogens?
extracellular bacteria intracellular bacteria fungi viruses parasites
two extremes of pathology?
bacteria that result in single toxin or attach to surface epithelial (needs antibody neutralization)
bacteria that are not toxic and cause disease by invasion of tissues (needs mediated immunity)
extracellular bacteria
replicate outside host cells
innate response to extracellular bacteria?
epithelial barrier, flora
alternative C’
phagocytes (macs and neutros)
pro-inflammatory cytokines
PAMP recognition
C3 - alternative C’ > C5a C3a
may lead to clotting and fibrin formation
adaptive immune response to extracellular bacteria?
antibody production and activation CD4+
helper T cells produce cytokines for B cell response, macrophage activation, and inflammation
opsonization?
extracellular bacteria
antibody and complement
SIRS
systemic inflammatory response syndrome
what can lead to endotoxic shock?
LPS
what are the results of TNF and IL-1
cause endothelial cells to express cell adhesion molecules and thromboplastin
promote adhesion of cells and fibrin deposition
enhanced by PAF
how do gram + bacteria induce shock?
massive release of cytokines (storm) by superantigens
how to block shock?
TNF neutralizing antibody
thromboplastin antibodies
PAF and NO inhibitors
not useful clinically (only modeled experimentally)
how do bacteria evade complement?
- outer capsule with no complement binding
- outer surface so phagocytes can’t access bound C3b
- surface structures that divert the MAC away
- membrane enzymes can degrade complement
- outer membrane can resist insertion of MAC
- secrete decoy proteins that cause complement to be deposited on them and not on bacterium
how do bacteria and fungi evade phagocyte killing?
- repellent or toxins that inhibit chemotaxis
- capsules that inhibit phagocyte attachment
- once phagocytosed, release factors blocking killing
- catalase - breaks down H2O2
- resistant outer coats
- lipoarbinomannan - block ability of macrophages to respond to IFN-gamma
- impair antigen presenting function
- escape phagosome and multiple in cytoplasm
- organism can kill phagocyte via necrosis or apoptosis
neisseria gonorrhoeae
bacteria
- IgA protease
- blebs membrane to soak up antibody
- LPS is sialylated
- phase variation - alternative set of surface molecules
- genes for pilus under go recombination
rickettsia
intracellular bacteria
