Innate Immunity Flashcards
Describe features of the innate immune system
- rapid response (minutes/hours)
- recognises a limited number of different structures characteristic to pathogens
- no change upon re-exposure
Describe the features of the adaptive immune system
- takes time to develop (days/weeks)
- highly specific for a vast number of different structures
- response improves upon re-exposure
What can a hematopoietic stem cell differentiate into?
- common lymphoid progenitor
- common myeloid progenitor
What cells are involved in the innate response?
- NK cell
- dendritic cell
- monocyte
- neutrophil
- eosinophil
- basophil
- mast cell precursor
What are the cells involved in adaptive response?
- T cell
- B cell
- Dendritic cell
Where are monocytes released from?
-bone marrow
When do monocytes differentiate into macrophages?
-when they leave the blood stream
What are the main roles of monocytes?
to phagocytose and kill bacteria and to remove apoptotic cells
What can macrophages recognise using what?
can use pattern recognition receptors (PRR) to recognise pathogen associated molecular patterns (PAMPS)
How do macrophages kill bacteria in phagolysosomes?
- acidification
- production of oxygen and nitrogen radicals
- proteolytic enzymes
How does antigen presentation occur?
- peptodes derived from killed microbes are presented to effector T cells, leading to their stimulation
- activated T cells will then support macrophages by soluble and surface-bound signals
What are cytokines and where are they released from?
-small proteins released from activated macrophages
What is the role of cytokines?
- to attract other immune cells to the site of infection,causing inflammation
- can act systemically and locally to activate antibacterial immunity
What is the role of Kupffer cells?
remove circulating bacteria and apoptotic cells in the liver sinusoids
What is the role of alveolar macrophages?
remove inhaled pathogens and other particles from the lungs
What is the role of osteoclasts?
regulate bobe density
What is the role of microglial cells?
scavenge dead cells, plaques and microbes in our brain
What are the features of neutrophils?
- most abundant leukocytes
- short lifespan (1-3 days)
- circulate in blood unless recruited to site of infection
- phagocytose and kill bacteria
- vitally important in defence against bacteria
When do neutrophils enter the tissue?
if they detect signs of inflammation displayed on the endothelium
How do neutrophils enter tissues at the site of infection?
- when inflammation occurs the vasculature express E-selectin proteins which the neutrophil recognise
- the neutrophil slows down in the process of rolling
- the neutrophils will then begin to react with other receptors (e.g chemokines and cytokines) this causes tight binding to the vasculature
- the neutrophil them migrates through the endothelium
- once inside the neutrophil migrates to the site of infection (follows gradient of CXCL IL-8)
What does bacteria triggering macrophages lead to?
- the release of cytokines and chemokines
- vasodilation, increased vascular permeability (redness, heat swelling)
- inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain
Describe how neutrophils respond on pathogens
- engulf microbe
- bacterial peptides activate Rac2 and bacteria are taken up in the phagosome
- phagosomes fuse with primary and secondary granules Rac2 induces assembly of a functional NADPH oxidase in the phagosome membrane, leading to generation of O2-
- acidification as a result of ion influx release granule proteases from granule matrix
What are eosinophils, basophils and mast cells used for in innate immunity?
mainly involved in defence against pathogens that are too large to be phagocytosed such as parasites (also involved in allergic reactions)
What are NK cells?
- natural killer cells
- recognise virally infected cells by recognising patterns specific for viral infection
- release granules to kill infected cells
- dead cells are removed by macrophages or neighbouring cells
What is the role of dendritic cells?
-take up microbial material, migrate to lymph nodes and initiate T cell responses
What is opsonisation?
increased phagocytosis of bacteria
What happened when complement factors interact with bacterial surfaces or antibodies?
-cleavage and activation of these proteins
which contribute to:
-killing bacteria
-inflammation
