3.9 Flashcards
Cell death
Lysis of host cells
1. growth of pathogen within host cells
• Cell membrane damage causes cell death (free radicalinduced lipid peroxidation). • Damage is proportional to number of bacteria inside cell.
- Cell death (continued)
Lysis of host cells - cell-mediated immunity
activated CD8+ cell encounters infected cell displaying pMHC class 1 reactivated CD8+ cell proliferated and makes contact with other cells that display the same pMHC class 1 CTL use perforin and granzymes to kill cells displaying appropriate pMHC class 1
- Cell death (continued)
Lysis of host cells - Membrane-damaging toxins
Apoptosis (programmed cell death)
Damage caused by host responses
Uncontrolled inflammation
due to
exaggerated adaptive immune response = hypersensitivities
Inflammation (3)
– healthy response
- increased blood supply (redness)
- increased vascular permeability (edema)
- chemotaxis (infiltration by phagocytes and
lymphocytes)
Type I hypersensitivity =
allergy but can lead to
anaphylaxis and shock
Type II hypersensitivity =
bound
antibodies leading to complement
and leukocyte activation to surfaces
Type III hypersensitivity =
bound antibodies
leading to complement and leukocyte
activation to soluble molecules, then immune
complex deposition (e.g in glomeruli)
Type IV hypersensitivity =
inflammation by purely CMI
responses (not antibodies)
Alteration of the metabolism of host cells
caused by —
toxins
Toxins
Microbial product or component that can injure another
cell or organism at low concentrations
Toxins act in different ways: (3)
Modulation of targets inside a host cell
Action in the extracellular matrix
Action on surface of a host cell
Toxin production and disease consequences vary widely
among
pathogenic bacteria
Like transposons, many toxin-encoding genes are carried
on
plasmids or temperate bacteriophage genomes (easy to
transfer to other, non-toxigenic bacteria).
ctxA and ctxB encode the
proteins that comprise
cholera toxin
