Mechanisms of bacterial toxicity Flashcards
what are the two ways in which bacteria cause damage?
- -colonise the body surface and only invade the tissue to a limited extent.
- -cause damage by invasion and subsequent multiplication in tissues.
what are the six innate defense mechanisms?
- –skin aided by acidic skin secretions
- –mucus traps invading organisms
- –external secretions contain antibacterial proteins
- –coughing and sneezing expels pathogens
- –acidic secretions in stomach
- –commensals
what is opsonization?
coating of bacteria by antibody or complement.
what is the role of complement?
- –formation of membrane attack complex
- –chemotaxis and activation of phagocytosis
- –opsonization
what is the role of the antibody?
neutralisation of bacterial toxins
opsonization
how does IgA cross the epithelial memebrane?
IgA binds to poly Ig receptor
secretory component on secreted IgA
what are NK cells?
part of the innate system and a re large granular lymphocytes that destroy virally infected cells
what is the role of interferon?
cell infected by virus is stimulated to produce alpha and beta interferon which signal neighboring cells to produce anti-viral proteins.
what is alpha and beta produced by?
leukocytes
fibroblasts
virally infected cells
what is interferon gamma produced by and what does it do?
activated T-cells up-regulate the MHC class 1 which present viral peptides cytotoxic T-cells.
how does the immune system react to parasitic worms?
Eosinophil granules contain substances toxic to parasitic worms
mast cell and basophil degranulation also occurs.
what is the role of lysozyme?
lyse the bacterial cell wall.
how does the conjunctiva protect the eye?
forms part of the eye associated lymphoid tissue(EALT)
EALT consists of a diffuse lymphoid tissue of T lymphocytes and IgA from secreting plasma cells.
why do few microorganisms bind to cornea?
membrane bound mucins prevent attachment of microorganisms.
Langerhans concentrated in the peripheral cornea act as antigen presenting cells.
why does corneal transplantation have a high success rate?
avascularity of cornea and lack of immune activation.
