Innate Immunity Flashcards
What is the immune system? What does it provide? What happens in its absence? Promiscuous?
- comprised of cells dedicated to the defense of the human body
- crucial to human survival
- provides immunity that will protect against disease, pathogens
- it its absence, even minor infections can result in fatalities
- promiscuous- swap genetic material
What is a pathogen? When does a pathogen cause disease?
- pathogen- any organism that has the potential to cause disease
- some cause disease upon entering the body
- others colonize the body with no ill effect, but cause disease if the body’s defenses are weakened or microbe gets in the wrong place (opportunistic)
What are the two arms of the immune response?
- innate- natural
- acquired/adaptive- specific
How much of innate immunity is natural?
70-75%
- in our body WBCs have short life span, quick turnaround
- precedes adaptive immunity
Acute immunity is due to what type of immunity? chronic?
acute- innate
chronic- adaptive
What are some characteristics of innate immunity?
- innate defense mechanisms are present prior to exposure to infectious microbes or other foreign macromolecules
- first lines of defense (within hours)
- not specific for any particular agent
- evolutionarily more primitive
- no memory
- quick turnaround, cells cycle every 30 days
Characteristics of specific immunity?
- evolutionarily more advanced
- usually responsible for resolving infection
- slower
- often confers life long immunity (memory)
- usually specific for a particular organism
- preceded by innate
What type of barriers make up innate immunity?
- physical barriers
- skin
- mucosal surfaces
- chemical barriers
- normal flora- skin, GI, vagina bacteria
- mechanical barriers
What is the first line of defense in innate immunity? what breaches it?
- skin-forms impenetrable barrier protected by layers of keratinized cells
- breached by physical damage- wounds, burns, surgery
What areas have mucosal surfaces? How does mucus protect?
- respiratory tract
- GI tract
- urogenital tract
- lined with thick layer of mucus
- trap the microorganism and constantly move mucus up and out
What are chemical barriers in innate?
- pH of stomach, vagina, skin
- degradative enzymes
Examples of degradative enzymes and how they protect?
- tears and saliva contain lysozyme- degrade bacteria cell walls
- epithelial surfaces secrete defensins (small charged molecule)- perturb membranes of bacteria, fungi, enveloped viruses
- digestive enzymes and bile in small intestine
Examples of mechanical barriers in innate?
- flushing- tears, urination, vomiting
- coughing
What is the general action of innate immunity (2 parts)?
- recognition of the pathogen by soluble proteins and cell surface receptors
- recruitment of effector mechanisms that kill and eliminate
What recognizes pathogens in innate (4)?
- Pathogen associated molecular patterns (PAMPs)- respond to foreign invaders
- Damage associated molecular patterns (DAMPs)- respond to any signal of damage
- Toll like receptors (TLRs)- respond to intracellular stimuli, peptides, nucleic acids
- Nod like receptors (NLRs)
What effector mechanisms kill in innate?
- mechanisms provided by effector cells that engulf pathogens
- serum proteins (complement) that mark pathogens or attack pathogens
What is innate immunity composed of?
- molecules:
- cytokines- follows chemical gradient
- complement- triggers direct lysis - cells:
- granulocyte
- growth factors
- machrophages/monocytes/dendritic cells (cell mediated)
What is complement? What does activation result in?
- plasma proteins that act in a cascade of reactions to attack extracellular forms of pathogens
- activation results in pathogens becoming coated with complement components killing pathogens directly or facilitating engulfment and destruction of phagocytes
What are phagocytes?
- cell specialized to engulf and destroy pathogens
- eat other cells
What is phagocytosis? What cells do it?
- ingestion and destruction by individual cells of foreign particles(bacteria)
- cells that do it:
- mononuclear phagocytes
- macrophages, dendritic
- neutrophils
What are neutrophils? Where are they most prevalent? What is their lifespan? when do they arrive? when do we produce them?
- polymorphonuclear leukocytes(granulocytes)
- most prevalent kind
- most lethal phagocytes, sloppy
- 24-48 hour lifespan -arrive in 4-6 hours
- always being produced
Why are neutrophils important in innate immunity?
- can be rapidly mobilized to enter sites of infection
- can work in anaerobic environments
- form pus- destroy tissues around problem
Where do neutrophils arise from? why are they called neutrophils? What is the shape of the nucleus? How do they work?
- arise from myeloid differentiation
- prominent neutral cytoplasmic granules
- contain reactive substance that kill microorganisms and enhance inflammation
- nucleus is irregularly shaped and multi lobed
- phagocytosis- capture, engulf, and kill microorganisms
What are eosinophils? what do they defend against? lifespan?
- granules stained with eosin
- defends against helminths and intestinal parasites
- less than a week lifespan
What are basophils? Functions?
- least abundant granulocyte
- granules stained with hematoxylin
- little known about function- maybe allergy
Name the polymorphonuclear leukocytes (granulocytes)?
- neutrophils
- eosinophils
- basophils
What are monocytes? where are they found? size? nucleus shape? lifespan?
- give rise to macrophages, dendritic cells
- circulate in blood
- bigger than granulocytes
- indented nucleus
- dont have granules
- longer lived
- differentiate into different macrophages in different tissues
What are macrophages? shape? function? lifespan?
- differentiated tissue phagocytes arising from monocytes
- irregularly shaped cells with extensive cytoplasm and numerous vacuoles
- scavengers
- dispose of dead cells and debris
- process and present antigen to T cells
- secrete cytokines that regulate other cell types(neutrophils, leukocytes)
- bridge between innate and acquired
- longer life than neutrophils
What are dendritic cells? where do they arise from? shape? properties? function? lifespan?
- arise from myeloid differentiation-monocytes
- star shaped
- properties common to macrophages
- function to initiate adaptive immune responses
- pick up antigen in infected tissue -move to lymphoid tissue
- live for 1 year
What is the overall effect of the innate immune response? characteristics of inflammation?
- induce a state of inflammation- acute, temporary
- heat, pain, redness, swelling
- sunburn causes cell death, inflammation takes care of it
What is the process of surface injury leading to inflammation?
- surface wound introduces bacteria
- resident effector cell are activated to secrete cytokines
- cytokines change properties of endothelium
- vasodilation and increased vascular permeability allow fluid, protein, inflammatory cells to leave blood and enter tissue (complement)
- infected tissue becomes inflamed, causing redness, heat, swelling, pain
what are cytokines? What secretes them? Function?
- soluble, hormone like molecules
- secreted by cells of the immune system
- act on cells by binding to specific receptors
- influence cell activity- proliferation, activation of function
What happens in fever? What are some molecules involved in fever?
- release of endogenous pyrogens
- IL-1 (interlukin 1)
- IFNs (interferons)
- TNF-a(tumor necrosis factor alpha)
- produced by resident cells, change proteins of endothelial cells
What are the primary lymphoid organs?
- thymus- T lymphocytes
- bone marrow- myeloid cells, B lymphocytes
What are the secondary (peripheral) lymphoid organs?
- tonsils, adenoids
- spleen
- lymph nodes
- mucosal surfaces
What is the relationship between primary and secondary lymphoid organs? Where are most of our defenses?
- primary- lymphocytes are created here
- secondary- migrate to these sites and stimulate adaptive immune response
- this is where innate and adaptive immunity meet
- most defenses by orifices, bacteria enters here
Where is the site of lymphocyte stimulation?
draining lymph nodes
What happens when you lack innate immunity? adaptive?
- no chance for immune response- worst case
- compromised immunity, long term problems
