L13 Innate Immunity Flashcards
What is innate immunity
Immediate response to a pathogen that does not confer long lasting protective immunity.
Non specific defense system
What Are the 3 phases of response to initial infection
Innate immunity(0-4 hrs)
Early induced innate response(4-96hrs)
Adaptive immune response(>96 hrs)
What are innate immune mechanisms
Act immediately
Followed by early induced responses which can be activated by infection but do not generate lasting protective immunity
When would adaptive immunity occur
Only if an infectious organism can breach these lines of defense will an adaptative immune response ensue with the generation of antigen specific effector cells that specifically target the pathogen and memory cells that can prevent reinfection with the same microorganism
What are the cells of innate immunity
Neutrophils Monocytes Natural killer cells Eosinophils Basophils
First responders to infection and phagocytose bacteria in to phagosomes before hydrolyzing and destroying them
Neutrophils
Rapid response and not prolonged effect
Neutrophils
Phagocytose pathogens
Macrophages
When do monocytes become macrophages
When they are in tissues
Provide prolonged defense
Monocytes
What are natural killer cells and what do they do
Large granular lymphocytes that recognize non specifically the surface changes on tumor cells and virus infected cells and damage these cells without prior sensitization
Cells that fail to express MHC class 1 molecules
Natural killer cells
What is the process of ADCC and which cell carries it out
Natural killer cell
Binding to antibody already attached to antigen on a target cell using their Fc receptors
Naturally present in spleen and peripheral blood
Natural killer cells
Have granules containing a variety of enzymes and toxic proteins which are released when these cells are activated
Eosinophils and basophils
Which cells are Important against defense of parasites and why
Eosinophils and basophils as they are too large to be ingested by macrophages or neutrophils
What are the barriers to infection
Epithelial layers
Antimicrobial substances
Where are epithelial cells a barrier and how
Skin Airways GIT Genitourinary tract Have tight junctions and produces a number antimicrobial peptides that help provide protection against invading pathogens
What are the antimicrobial substances
Lysozyme
Defensins
Lactoferrin
What is the lysozyme and what does it do
Tears mucus saliva
Splits the sugar from the mucopeptide layer of the cell wall of gram positive bacteria
What are defensins and what do they do and where are they produced
Peptides produced by neutrophils epithelial cells and other cells that disrupt microbial membranes
Primarily produced in GIT and lower respiratory tract that create pores in lipid membranes of bacteria fungi and some viruses
What is lactoferrin and what does it
Iron binding protein
Deprives micorbes of the free iron they need for growth
How does mucous protect
Trapping mechanism
And action of cilia sweeps secretion with inhaled microorganisms either outside through coughing and sneezing or towards stomach where they are acted upon by hcl
Describe phagocytosis
1–phagocytic cells engulf microorganisms and remove them from lymph and blood stream
2-phagosome containing microbe fuses with lysosome
3-microbe is killed within phagolysosome by proteases as well as by reactive oxygen species and reactive nitrogen radicles
How can phagocytosis be enhanced
enhanced by opsonization of the particles by opsonin which include complement fragments C3b and IgG
What are the pattern recognition receptors of innate immunity cells
Toll like receptors
Nucleotide binding oligomerization like receptors
What are toll like receptors
They are a group of pattern recognition receptors found either on the surface or in the endosomal compartment of innate immune cells such as macrophages and dendritic cells they are glycoprotein in nature and are an important part of innate immunity
What do toll like receptors recognize and bind to
they recognize and bind to highly conserved structures present in different organisms known as pathogen associated molecular patterns
What do PAMPs include
1-Bacterial components as flagellant peptidoglycan Tiechoic cells lipopolysaccharides
2-Fungal molecules as zymosan and mannas
3-viral molecules as viral nucleic acid and proteins
What do cell surface TLRs sense
And what do those in endosomal compartment bind to
Cell surface TLR‘s typically sense PAMPS of microbial cell envelopes flagella or Lipopolysaccharide
In the endosomal compartment bind to nucleic acids
What happens after binding of TLRs to PAMPS of bacteria and fungi
Triggers the activation of signal transduction pathways resulting in the activation of innate immune cells and synthesis of cytokines as IL2 IL8 and TNFa that in turn triggers immune defenses as inflammation,fever and phagocytosis
binding of TLRs to viral components trigger synthesis of interferon and blocks viral replication
Describe nucleotide binding oligomerization domain like receptors
They are specialized set of intracellular cytosolic receptors that are essential components of the innate immune system and function by the recognition of cytoplasmic PAMPS resulting in activation of signaling pathways
What is the result of NLRS activating signaling pathways
Production of cytokines and chemokines which alert the immune system to the presence of pathogenic bacteria and Aid in the clearance of infection
What is inflammation
Acute local inflammation as an early defense mechanism to contain the infection prevent its spread from the initial focus and activates subsequent immune response
How does fever protect organism snd how is it triggered
Triggered by resetting hypothalamic thermostat triggered by toxins or cytokines
The higher temperature inhibit bacterial growth intensifies the effect of antiviral interferons and speeds of the body‘s reaction aiding tissue repair
Complement system
It is another key component of innate immunity the alternative and lectin pathways of complement activation serve as critical first line of defense and provide immediate protection against microorganisms
