Immunity Flashcards
What is the purpose of the acute inflammatory response?
1) Neutralize and destroy harmful agent
2) Localize injury
3) Allow healing
What are the cardinal signs of inflammation?
1) heat
2) redness
3) swelling
4) pain
5) +/- loss of function
What factors determine the intensity and extent of the inflammatory response?
1) the severity of the injury
2) the reactive capability of the host
What are the five causes of inflammation?
1) surgery or physical trauma - mechanical injury
2) UV/radiation
3) chemicals
4) microbes/bugs
5) ischemia
What are the 3 events of the inflammatory process?
1) release of chemical mediators
2) vascular response
3) cellular response
What are the key properties of the acute inflammatory response?
- non-specific
- no memory is created
- short duration (8-10 days)
What are the five chemical mediators involved in AIR?
1) histamine
2) leukotriene
3) prostaglandin
4) bradykinin
5) platelet activating factor
What is inflammation?
A homeostatic process that is activated by cellular injury - regardless of the mechanism of injury.
What are the properties of histamine?
- 1st and most abundant mediator released *
Derived from mast cells (connective tissue - skin, respiratory, GI)
Involved in allergic reactions
What are the effects of histamine?
Vasodilation
Endothelial cell retraction = increased CMP
How are prostaglandins produced?
Produced via cellular injury:
Injured cells release arachadonic acid — processed via cyclo-oxygenase pathway — results in prostaglandins
What are the effects of prostaglandins?
Vasodilation
Increased CMP
Chemotaxis
Pain
How are leukotrienes produced?
Produced via cellular injury;
Arachadonic acid is processed via lipo-oxygenase pathway— results in leukotriene production
What are the effects of leukotrienes?
Chemotaxis
Increased CMP
Neutrophil aggregation
What are the properties of bradykinin?
Plasma protein produced via the kinin cascade - injured cells release clotting factors (Hageman factor)
What are the effects of bradykinin?
Vasodilation
Endothelial cell retraction = increased CMP
Chemotaxis
Pain
Which five cells release platelet activating factor?
Mast cells
Neutrophils
Monocytes
Endothelial cells
Platelets
What are the effects of platelet activating factor?
Increased CMP
Platelet activation
Leukocyte adhesion to endothelium (allows them to stick to area of cellular injury)
What are the five steps of the vascular response (AIR)?
1) vasoconstriction
2) vasodilation
3) increased increased capillary membrane permeability
4) platelet adhesion
5) slowed circulation
Explain the vasoconstriction step in the vascular response (AIR)
Occurs briefly and immediately after injury – is a mechanism to prevent bloodloss
Explain the vasodilation step in the vascular response (AIR)
Occurs due to release of chemical mediators - histamine, prostaglandin, bradykinin
Purpose: to increase blood flow to the site of injury
Increased blood flow increases hydrostatic pressure = results in fluid being pushed out of the vasculature (swelling)
Explain the step of increased capillary membrane permeability in the vascular response (AIR).
Occurs due to the release of chemical mediators that cause endothelial cell retraction - histamine and bradykinin
Purpose: dilute toxins if present and shift plasma fluid out of the vasculature into the interstitial space
Result: increased blood viscosity, WBC emigration to site of injury
edema, pain, +/- loss of function
Explain the platelet adhesion step of the vascular response (AIR).
Platelets move to site of injury and stick to exposed collagen of vasculature - coagulation occurs
Purpose: clot formation to localize injury and prevent spread of pathogen
Also prevents widespread/systemic inflammatory response
Explain the slowed circulation step of the vascular response (AIR).
Fluid shift caused by vasodilation and increased CMP = increased blood viscosity which slows blood flow
Purpose: allows WBCs to marginate and get to site of injury to start cellular response
What are the four steps of the cellular response (AIR)?
1) margination & pavementing
2) emigration of WBCs via diapedesis
3) chemotaxis
4) phagocytosis
Explain the step of margination and pavementing in the cellular response (AIR).
Pavementing: the cobblestone appearance from neutrophils and monocytes migrating along the vessel wall
Facilitated by selectin
What is selectin?
An adhesion protein presented by endothelial cells to facilitate margination
How is pavementing different from the normal physiological relationship between blood cells and the endothelium?
Endothelial cells normally produce nitric oxide to repel blood cells away from vessel walls
**response in inhibited during AIR
Explain the emigration of WBCs during the cellular response of AIR.
Neutrophils and monocytes pass through the capillary wall (made possible by endothelial cell retraction) to get to the site of injury
What is diapedesis?
Process of the WBC leaving the vasculature – WBC sticks its foot our through the gaps in the capillary wall from endothelial cell retraction
What is integrin?
An adhesion molecule on the WBCs surface - it binds to selectin on endothelial cells
Helps to catch the WBCs so they can leave the vasculature
Explain the step of chemotaxis in the cellular response of AIR.
Chemotaxis: the process of WBCs being drawn to the site of injury
Occurs due to release of chemical mediators - prostaglandin, bradykinin, leukotriene
Explain the step of phagocytosis in the cellular response of AIR.
The 4-step process of phagocytes (neutrophils and monocytes) ingesting and destroying antigens/microorganisms/debris
What are the four steps of phagocytosis?
RAID
Recognition
Attachment
Ingestion
Digestion
Explain the recognition step of phagocytosis.
Phagocyte must recognize the pathogen/antigen as foreign
Accomplished through:
(PAMP) pathogen associated molecular patterns
(PRR) pathogen recognition receptors
or antibodies
Explain the attachment step of phagocytosis.
Phagocyte attaches to surface of pathogen via opsonization or binding sites
What is opsonization?
The process of covering an antigen with opsonins (immunoglobulins and complement C3b) to make it more susceptible for phagocyte ingestion because they provide more binding sites for attachment
** increases effectiveness of phagocytosis **
What is an opsonin?
A normally inactive protein in the bloodstream that is activated with the activation of the complement system
Explain the ingestion step of phagocytosis.
The cell membrane of the phagocyte extends projections (pseudopods) that wrap around the bacteria, then meet and fuse to encapsulate the bacteria in a phagosome
Explain the digestion step of phagocytosis.
The phagosome fuses with lysosomes creating a digestive vacuole called a phagolysosome
Lysosomes destroy the antigen
Antigen is broken down into small protein fragments and spit out via exocytosis