Block 3 Flashcards
what does rhinovirus infect
epithelia cells which leads to a cold
what does hepatitis A-G infect
liver cells
what does HIV infect
CD4+ T cells which leads to Aids
innate immune response for viruses
Type-1 interferon (IFN)
NK cells
Dendtritic cells
adaptive immune system response for viruses
CD4+ helper T cell
CD8+ cytotoxic T cell
B cells
where is cytokine production incduced
virus-infected cells
what does Type-1 IFN do
Induces cells to shut down some of their protein-making functions.
Activates immunoproteasome activity and increases MHC expression
Activates dendritic cells, macrophages and NK cells
how do some viruses try to evade immune response
by switching off MHC-1 expression or inhibiting the processing pathway
what do activated NK cells produce
IFN gamma, which helps activate macrophages and induces T cells towards Th1 phenotype
what are NK cells activated by
recognition of ‘altered self’ altered surface proteins on infected cells suggest infection
what does reduced levels of MHC-1 allow
virus-infected cells to evade cytotoxic T cells
how are cytotoxic T lymphocytes activated
by recognition of specific viral antigen on MHC-1
what activates apoptosis
release of intracellular granules
what do antibodies do
bind to virus proteins and target for destruction, block viral proteins, neutralise viral toxins
what is a parasite
organism that benefits at the expense of another host organism
what cells do not express MHC molecules
Red blood cells
healing response to Leishmania major
macrophage/dendrtitic cells produce IL-12 activating macrophages to kill the intramacrophage parasite.
IFN-gamma from NK cells, TH1 cells activate macrophages which produce microbicidal products eg superoxide, nitric oxide, enzymes
cutaneous leishmaniasis
no activated macrophages, TH2 dependent, IL-4 drives a TH2 response, Th2 cells produce IL-4/IL-13 which inhibit a TH1 response by inhibiting IL-12 production. IL-4/IL-13 inhibit IFN-gamma production and activity
toxoplasma gondii
CD8+ T cells producing IFN-gamma main mediators of resistance
In AIDS patients dormant tissue cysts in the brain reactivate resulting in encephalitis
IgG-coated parasites are killed inside macrophages following phagolysosome fusion
what does antigenic variation result in
parasite persistence
how do the different cell-mediated responses recognise bacteria
Innate- pathogen recognition receptors (PRR)
Adaptive- B/T cells recognise their specific antigen
how do neutrophil extracellular traps (NETs) respond to bacteria
immobilise bacteria at the site of infection, specialised apoptosis (NETosis)
complement-mediated killing of bacteria
Direct lysis of bacterial cell using full pathway
Indirect – act as an opsonin to aid phagocytosis
antibody response to bacteria
bind to bacterial toxins, neutralise effects – stop toxin reaching its active site. Act as an opsonin–clumped bacteria easier to be taken up by phagocytes
Bacteria produce super antigens – class of proteins that can activate a large population of T cells – induce toxic shock
T cells response to bacteria
produce cytokines- act on intracellular bacteria interferon-gamma, CD8+ T cells and CD4+ TH1 cells
Kill cells by apoptosis
how is cancer caused
uncontrolled replication of a cell
what is caused by smoking
chronic inflammation which causes an imbalance in cytokine secretion and inflammatory responses
intrinsic cancer pathway
series of genetic events (e.g. activation of oncogenes, inactivation of tumour suppressor genes) causing neoplastic transformation
extrinsic caner pathway
inflammatory leukocytes and soluble mediators maintain inflammation at a site and increase cancer risk
Cancer cells can remain localised or spread through the body (metastatic)
what do cancer cells not express
MHC molecules
what do cancer cells express
antigens with poorly immunogenic epitopes
what do cancer cells release
immunosuppressive cytokines- TGF- beta used by tumours. causes CD4+CD25 => CD4+CD25+ Treg cells – switch off cytotoxic T cells. Induce the development of Th17 and reduce the fraction of activated Th cells
Th2 cytokines
what qualities do M2 Macrophages
anti-inflammatory qualities to protect host tissues and produce numerous growth factors
