The immune system and disease 1 Flashcards
Function of macrophages
Sentinels under skin/gut/resp mucosa. Process cellular debris. Act as APC if primed , activate T cells and can directly kill pathogens also.
MHC expression in macrophages
MHC II- low levels in normally upregulated when activated
How are macrophages activated?
When barriers are penetrated, NK and T cells release IFNg which activates T cell
How does macrophage recognise pathogens?
PRR (eg Toll like) on macrophage recognise PAMPs- non-specific
How does a macrophage become a more effective killer when hyperactivated?
Increases reactive oxygen molecules and number of lysosomes
Cytokines secreted by activated macrophage
IL-1B, TNF-a, IL-4, CXCL-8, IL-12
Macrophage response to activation (receptors)
Upregulate MHC and costim molecules (CD80 CD86) and increase capillary endothelial cell adhesion molecule expression (allow extravasation)
Macrophage response to activation (pathway activation and cytokines)
Activates complement cascade
TNF-a secretion (activates vasc endothelium, increase vasc permeability allowing more complement, Ig, cells and fluid to the site)
NK cells origin
Bone marrow
NK cells receptors- specific or non-specific?
Non-specific
NK cell function
Kill tumour and virally infected cells
Also secrete IFN-g to activate macrophages
How are NK cells further activated?
Macrophages secrete TNF-a and IL12 which further activates NK cells
Neutrophils origin and life span
Bone marrow derived, 5 day life span
Neutrophil function
Ingest and kill microbes - not APC
How are neutrophils attracted to infection site?
TNF-a
Dendritic cell origin
Bone marrow derived
Resting dendritic cell function and features
Sentinel beneath epithelial barriers, sampling the environment and with low levels of B& (costim) and MHC I&II - bridges innate and adaptive immunity
How are dendritic cells activated and what happens?
They are activated by IFNg or TLR stimulation, upregulate B7 and MHC I&II, phagocytose pathogen and then travel to lymph node.
What do activated dendritic cells do at the lymph node?
Sampled by T-cells and activate one with the right receptor
Secrete chemokine to attract monocytes to infection and continue sampling the site
How long does the dendritic cell survive at lymph node and what is the significance of this?
7 days - if pathogen still present at site of infection, need new dendritic cell to come to the lymph node and activate T cells
