Immunity to pathogens Flashcards
(19 cards)
How does infection by pathogens cause disease?
Either by host cell death or toxin production
List some of the receptors involved in the innate immune response
- TLR
- N-formyl-methionyl receptor
- Mannose receptor
What do T1 cells trigger?
IFN-y and TNF
Results in CMI triggered due to macrophage activation
What do Th2 cells do?
Secrete IL-10, IL-4 and IL-5 which both inhibit microbicidal function of macrophages and promotes mast cells, eosinophils and IgE
What triggers macrophages?
IFN-y
What is the main cause of tissue damage in intracellular bacterial infections?
The hosts delayed type hypersensitivity response
Describe cell mediated immunity
- Adaptive
- T cells activate phagocytes to eliminate microbes
How do extracellular bacteria evade the IR?
- Inhibit the complement system (alternative pathway)
- Resistance to phagocytosis
- Antigenic variation in surface antigens
How do intracellular bacteria evade the IR?
- Inhibit phago-lysosome fusion
- Escape to cytosol
Describe innate immunity to viruses
- Infected tissue produced type 1 IFNs. Induced by TLR recognition of viral DNA/ RNA
- NK cells: active where virus inhibits MHC 1 CTL responses
- Apoptosis: mediated by host PKR kinase which inhibits protein synthesis in cells.
Describe adaptive immunity to viruses
- Neutralising antibody (prevents virus entry (IgA), removed free virus)
- CTL: MHC 1 restrictied killing of infected host cells
- Ab and complement mediated opsonisation for phagocytosis
Describe adaptive immunity to viruses
- Neutralising antibody (prevents virus entry (IgA), removed free virus)
- CTL: MHC 1 restrictied killing of infected host cells
- Ab and complement mediated opsonisation for phagocytosis
Which steps of immunity to virus provide protection against infection?
- Adaptive: neutralising antibody
- Innate: Type 1 IFN production puts tissue into antiviral state
Which steps of immunity against viruses provide eradication of the infection?
- Adaptive: CTL response
- Innate: NK cell response
Describe the two ways CTLs cause apoptosis of a cell
1) Granule exocytosis. Enter cell by perforin dependant mechanisms- triggers apoptosis pathway
2) FasL-Fas mediated, FasL on CTL interacts with Fas on target cell
How do viruses evade the IR?
- Inhibit antigen presentation (decoy MHC molecules, inhibit MHC synthesis, inhibit proteosomal activity)
- Inhibit apoptosis
- Inhibit interferons (Inhibit IFN signalling pathway, decoy receptors)
- Antigen variation
- Latency
Name an endoparasite which is often resistant to phagocytes and complement
-Helminths (have thick teguments)
How do the immune response deal with helminths?
- Th2 mediated
- IgE, mast cells, eosinophils
How does the immune response deal with protozoal infections?
Those captured by macrophages= Th1 CMI/ macrophage activation
-CTL killing of infected cells
