Innate Immune System Flashcards
What is immunology
The study of immunity
What is immunity
The body’s ability to protect itself against pathogens, itself, stopping irregular cell growth, toxins, mistakes in cell replication etc
What is a pathogen
A disease producing organism
Virus, bacteria, prion, Protozoa, helminth
What are some situations in which an understanding of how the immune system works is beneficial
Vaccinations
Disease processes (allergies)
Medications
Testing
True or false
Immunity and host defence mean the same thing
True
Describe the innate immune system and give an example
Non specific
Rapid
Consistent
Already exists in the body at birth
ex. Barriers, phagocytes, complement system, chemical barriers, physical barriers, rapid responders
What does it mean by the innate immune system being non specific
It does not change with repeated exposure, it always gives the same response
Describe the adaptive immune system
Specific
Discriminatory (self and non-self)
Has memory
Adapts to the situation in the body, and learns from previous exposures
Can be slow or rapid depending on if it’s been exposed to the pathogen before
Consists of specialist responders (respond to specific threats)
What are the 2 types of the adaptive immune system
Humoral mediated (bodily fluids)
Cellular mediated
What cells specialize in problems outside the cells
Phagocytes, complement system, antibodies
What cells specialize in problems within the cell
NK lymphocytes
Interferons
T lymphocytes
What is the innate immune system divided into
Fixed defences and mobile defences
What are the main fixed (external) defences of the innate immune system
Chemical barriers (gastric pH) Physical barriers (skin) Traps (nasal secretions) Elimination (coughing, urination) Commensal bacteria Antimicrobial chemicals (lysozyme, defensins)
What is lysozyme
Antimicrobial enzyme that digests cell walls
What are defensins
Antimicrobial proteins produced by epithelial cells and neutrophils. These make pores in cells walls of bacteria/fungi/viruses to allow them to lyse
Describe the innate (fixed) immune system found in hair and skin
Lubricated/protected by sebum (fatty acid that lowers pH)
Defensins (antimicrobial protein made by keratinocytes)
Commensal bacteria (fatty acids)
Tough and inert
Constantly shed
Tough, flexible, and resistant to chemicals
Repair of wounds (close openings to bacteria)
Describe the innate (fixed) immune system of the nose
Hairs (acts as a filter to trap pathogens so they are not inhaled)
Turbinates
Mucus (sticky, contains lysozyme)
Commensal bacteria
Describe the innate (fixed) immune system of the trachea
Cilia (tiny hairs sweep things out of the trachea) (mucociliary elevator) (physical structure)
What are some examples of physiological barriers
Tears
Blinking
Coughing
Sneezing
What is the innate (fixed) immune system of the stomach
Acidity of stomach acid (kills many pathogens)
What medicine interferes with the stomach acidity and can prevent normal protection from pathogens in this area
Antacids, ulcer prevention meds, these all decrease the acidity of the stomach acid (increase pH)
What is the innate (fixed) immune system of the small intestine
Sudden pH change from highly acidic to highly alkaline
Peristalsis (will move faster to remove pathogens)
Gut flora (compete for nutrients, produce antibacterial compounds)
Defensins
What medications interfere with the defences of the small intestine
Antibiotics (these target all bacteria, including good ones) or anything that slows down peristalsis
(This is why probiotics are used to replace bacteria)
These kill of all the good bacteria as well, allowing for the harmful bacteria to take over
Describe how blinking protects the eye
Physiological response
Protects from trauma and drying out
Tears: good for flushing and they contain lysozyme
What is keratoconjunctivitis sica (KCS)
DRY EYE
due to a lack of tears, makes the eye more prone to infection and ulcers
Describe the innate immune system of the urogenital tract
Flushing of the urinary tract
Vagina: Commensal bacteria, lactic acid (highly acidic to protect from infection)
What are some innate mobile defences
Phagocytes (neutrophils and macrophages/monocytes)
Killer (NK) lymphocytes
Complement system
Interferons
External barriers of the innate immune response are ____ and non specific
Immediate
Immunity is the process where ___ is distinguished from ____
Self
Non self
Once barriers have been breached by a pathogen, there must be a system to remove them once inside the body, describe the two methods used to identify foreign material in the body, how is this achieved?
Receptors that look for molecules/markers that are unique to pathogens (pattern recognition and lymphocytes antigen receptors)
An internal ID system that nearly all “self cells” carry
Accomplished by receptors in leukocytes and other immune cells that bind to pathogens or damaged tissue
Phagocytic cells of the innate immune system are directly activated by molecules common to pathogens using
pattern recognition receptors
True or false
There is only one type of pattern recognition receptors
FALSE
there are hundreds
Where are pattern recognition receptors found
Host defence cells (mainly sentinel/look out cells) (macrophages, dendritic cells, mast cells)
Neutrophils
Come circulate as part of plasma protein
What do cells with pattern recognition receptors do
Recognize (bind)
1) Basic components essential to pathogens (viral RNA, endotoxin of gram- bacteria)
2) molecules released from damaged tissue (heme)
The molecules that cells with the pattern recognition receptors bind to are_____ so normal cells are not attacked by accident
Not present in mammalian bodies
When pattern recognition receptors are activated or bound to, what does it stimulate
Inflammation
Anti parasitic activity
Initiates the adaptive immunity to create a memory
True or false
Most cells of the mobile innate immune system are either sentinel or phagocytic
True
What are sentinel cells
These are look out cells -alert the body of foreign material/bodies
Found at potential entry points
Activate immunity
Attract additional mobile defenders when needed
What are come examples of tissue sentinel cells
Macrophages
Dendritic cells/dendritic macrophages
Mast cells
Describe monocytes
Named for the single unit nucleus (Pleomorphic shape) (undivided)
Have pattern recognition receptors and antibody receptors
What is the function of monocytes
Phagocytic (remove dying neutrophils and tissue)
Sentinel (release mediators (cytokines) that stimulate innate and adaptive immune response)
Migrate into tissues to become macrophages and dendritic cells
Dead neutrophils are found most in areas of
Infection
Describe the similarities and differences between macrophages and dendritic cells
Macrophages: derived from blood monocytes
Dendritic cells: derived from monocytes or lymphoid cells
Both are sentinel, phagocytic and found in tissues
Macrophages: stay in tissue and remove neutrophils and damaged tissue -stimulates innate immunity
Dendritic cells: reside in and move to lymph nodes after phagocytosing foreign material -stimulates adaptive immunity
What are other names for neutrophils
Neutrophilic Granulocytes
Polymorphonuclear neutrophils (PMN) (deeply divided)
Band cells (immature) -nucleus is not divided)
A lot of band cells indicates
A severe infection -the body is making neutrophils faster and they don’t have time to mature (not as effective) but are made in severe situations
Neutrophils are one of the major WBCS: ___ %
40-75%
Describe neutrophils
Short life (days) Highly mobile
3 receptors:
1) patter recognition receptors for bacterial antigens -antigens common to microbes or damaged tissue (endotoxin)
2) antibodies (IgG) that have bound antigen
3) complement (blood Proteins activated by pathogens)
Mostly in blood
Rapidly migrate to inflammation sites
What are the functions of neutrophils
Phagocytose bacteria and other small foreign particles
Destroy ingested material using enzymes (lysozyme) or generating peroxides
Basophils (basophilic granules) are found in
Blood
These stain dark blue
Describe mast cells
Found in tissue, NOT blood, often with eosinophils
Similar to basophils (common bone marrow precursor)
Some mast cells arise from bone marrow and mature in tissues
Other mast cells differentiate from blood basophils
Dominant cell in allergies and anaphylaxis (stimulate complete degranulation)
What are the functions of basophils and mast cells
Sentinel
Activated by binding to: pattern recognition receptors or IgE
Release histamine and heparin from their granules when activated (increase blood flow in early inflammation)
What is IgE
An antibody which binds strongly to basophils and mast cells, when it binds to its appropriate antigen it activates the cell
This is an example of cooperation between innate and adaptive immune system
Describe eosinophils
Lobed nucleus with orange -red staining granules
Attracted by chemicals released from mast cells and pathogens
What are the functions of eosinophils
Produce, stores in granules and release externally:
1) proteins which destroy nearby tissues
2) peroxides
3) enzymes including RNAase
Important in defence against allergies and parasitic infections
Describe NK lymphocytes
Mononuclear
Circulate in blood and tissues (approx 20% of lymphocytes on a blood smear are NK)
Innate immune cells
These check to see if the cell is normal using an identification system
First responders to infection Known as MHC (first responders to viral attack in previously uninfected individuals)
Viral infections take over the cell’s production system which means it no longer produces MHC, what does this mean for NK lymphocytes
NK lymphocytes are activated by the absence of MHC
How to NK lymphocytes kill virus infected cells and tumour cells
Apoptosis (shutting down the cell)
Lyzing the cell
Describe the complement system
A group of blood plasma proteins (and inflammatory fluid), some of which made in the liver or by macrophages, parts of the innate immunity, act as a bridge between the innate and adaptive immune system
Some of these proteins are enzymes that activate other complement proteins in a cascade type reaction (central protein C3)
Describe the actions of the complement system
When activated, there is a variety of possible effects:
1) lysis of bacteria, cells and viruses
2) promotion of phagocytosis (opsonization) -this coats the pathogen to make phagocytes want it
3) triggers inflammation
What are the 3 possible pathways/methods of activation of the complement system
The lectin pathway
The classical pathway
The alternate pathway
What is the lectin pathway
Mannan-binding lectin
An acute phase reaction protein formed in the liver which binds to mannose sugars found on the surface of some pathogenic bacteria (this sugar is not found in mammalian cells) -this is an example of a soluble pattern recognition protein
When lectin is activated by binding, it triggers a cascade which then activates C3
What is the classical pathway (most effective)
Occurs in late infections because antibody has to be produced
Activated by an antibody binding to its antigen (part of a pathogen)
This causes a shape change in the antibody molecule which activates the first complement protein C1
C1 is an enzyme then activate other complement proteins
Final stage is activation of C3
What is the alternate pathway
C3 is an unstable protein that is constantly changing into its active form in plasma (spontaneous)
This is not a problem because healthy mammalian cell membranes inactivate C3
When C3 binds to bacterial cells, these have a different structure and C3 will continue to activate
The activation of C3 by any of the 3 pathways results in the same four effects
1) Opsonization (C3 fragments bind to bacteria and macrophages/neutrophils have receptors that bind to these fragments which make it easier to phagocytize the bacteria)
2) fragments attract immune cells (mainly neutrophils)
3) some stimulate mast cells to degranulate (release histamine to make capillaries leaky which bring in protein and immune cells more easily)
4) Formation of the “membrane attack complex” which is a group of complement proteins that binds bacteria or viral cell walls
What is interferon
A method of the innate immunity against viral infections
Produced by some dendritic cells, fibroblasts, and other cells
Rapid innate protection against viruses
What does interferon do
These recognize viruses using pattern recognition receptors
It results in rapid production of interferon (immediate -minutes)
It acts locally on infected AND non infected cells
Changes the cells metabolism so that it is more difficult for viruses to function
Also Triggers the cell to destroy itself (programmed cell death)
What is the significance of interferon
Interferon is used in therapy: recombinant feline interferon used to treat; dogs with parvovirus and cats with feline leukaemia virus (FeLV)
Some vaccines trigger interferon production (may give partial rapid protection while antibody levels build)
Interferon is an example of a
Antiviral
