Innate Immunity 2 Flashcards
What is the first step of the inflammatory response?
Chemical signals are released from resident cells (mast cells) and they act to attract more cells to the site of injury or infection
What happens after chemical signals are released from resident cells (mast cells) and they act to attract more cells to the site of injury or infection?
Neutrophils enter the blood from the bone marrow
What happens after neutrophils enter the blood from the bone marrow?
Neutrophils slow down and cling to the capillary wall
What happens after neutrophils slow down and cling to the capillary wall?
Chemical signals from tissue resident cells (mast cells) dilate the blood vessels and make capillaries leakier
What happens after chemical signals from tissue resident cells (mast cells) dilate the blood vessels and make capillaries leakier?
Neutrophils squeeze through the leaky capillary wall and follow the chemical trail to the injury site = producing inflammation
What cells are phagocytic?
Many myeloid cells
What is the first step of phagocytosis?
Phagocytes adhere to pathogens or debris (opsonised)
What happens after phagocytes adhere to pathogens or debris?
Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome
What is a phagosome?
A phagocytic vesicle
What happens after the phagosome is formed?
Lysosome fuses with the phagocytic vesicle, forming a phagolysosome
What happens after the phagolysosome is formed?
Toxic compounds and lysosomal enzymes destroy pathogens
What happens after toxic compounds and lysosomal enzymes destroy pathogens?
Sometimes exocytosis of the vesicle removes indigestible and residual materials
What features of the lysosome help to kill the phagocytosed microbes?
Low pH, reactive oxygen and nitrogen intermediates and digestive enzymes
What does a low pH do?
Gives an acidic environment
What are examples of oxygen and nitrogen intermediates?
Hydrogen peroxide and nitric oxide
What digestive enzymes are present in lysosomes?
Proteases, lipases and nucleases
What is the complement cascade?
9 major proteins/protein complexes (C1-9) which act in sequence to clear pathogens from blood and tissues
What is important to note about the complement cascade?
The proteins aren’t named in the order they act, instead, the order they were discovered
What are the results of the complement cascade?
Label pathogens (opsonisation), recruit phagocytes (chemotaxis) and destroy pathogens (lysis)
What are the 3 complement pathways?
Classical, alternative and lectin
What happens in the classical pathway?
Antibody boud to pathogen binds complement
What happens in the alternative pathway?
Pathogen binds to surface/pathogen component
What happens in the lectin pathway?
Carbohydrate components of microbes bind complement
When do the 3 complement pathways converge?
Where the C3 convertase (enzyme complex) is formed
What is the process which occurs during labelling?
Opsonisation
What happens in opsonisation?
Pathogens which bind to complement receptors on phagocytes are labelled
What protein is responsible for opsonisation?
C3b protein which is cleaved from C3
How are things labelled in opsonisation?
By coating a microbe with antibody and/or complement fragment C3b
What happens during the destroy result?
Membrane Attack Complex (MAC) formation
What is the MAC complex?
Pores in bacterial cells which cause death
What is the protein in the destroy result?
C9
What happens with microbes coated with C3b?
They are phagocytosed
What happens after microbes coated with C3b are phagocytosed?
The assembly of the MAC complex causes lysis
What happens during the recruit outcome?
Complement proteins act as peptide mediators of inflammation and recruit phagocytes
What proteins are involved in the recruit outcome?
C3a and C5a
What happens after complement proteins act as peptide mediators of inflammation?
Phagocytes are attracted to the site
What happens after phagocytes are attracted to the site?
Mast cells are degranulated by C3a and C5a
What happens after mast cells are degranulated by C3a and C5a?
Inflammatory mediators are released including proteins that attract phagocytes
