Innate Immunity, Inflammation, and Stress Flashcards
What are the three levels of immunity?
(1) first line of defense = innate (natural or native) immunity
making presence known
(2) second line of defense = inflammation
full force
(3) third line of defense = adaptive (acquired or specific) immunity
specific approach
Describe aspects of innate immunity
- natural physical barriers, mechanical, biochemical barriers
- inflammation
- in place at birth
Examples of physical barriers
- skin
- lining of gastrointestinal, genitourinary, and respiratory tracts
- mucous and cilia trap organisms and expel them through coughing, sneezing, urination, vomiting, and defecation
- low temp and low pH inhibit microorganism growth
Examples of cell-derived chemical barriers
- mucus, sweat, saliva, tears, earwax
- lysozyme attacks cell walls of gram-positive bacteria
- sebaceous glands secrete fatty acids and lactic acid that kill bacteria and fungi and create acidic pH
- antimicrobial peptides kill or inhibit growth of bacteria, fungi, and viruses (collectins and defensins)
Describe the normal microbiome
- each body surface is colonized by nonpathogenic microorganisms unique to the particular location and individual
- commensal or mutualistic relationship
Functions of the normal microbiome
- produces enzymes for digestions
- synthesizes metabolites
- releases antibacterial substances
- competes with pathogens for nutrients
- fosters adaptive immunity
- helps with communication between brain and GI tract
What are the categories of innate immunity white blood cells?
- endothelial cells (physical barrier)
- platelets
- granulocytes (release chemicals and phagocytize)
- agranulocytes (phagocytize)
Describe function and types of granulocytes
(1) neutrophils → first responder, phagocytosis
(2) eosinophils → release chemicals, allergy response, mildly phagocytize (parasites)
(3) basophils → release chemicals, allergy response
(4) mast cells → sentinel, release chemicals
Describe function and types of agranulocytes
Monocytes (macrophages) → inflammatory response, phagocytosis
Function of inflammation
- programmed response to damage/injury in the body/cell
- all or nothing first response → occurs in any vascularized tissue; rapid; nonspecific
Benefits of inflammation
- generates new tissue
- limits and controls inflammatory process → clotting, plasma enzymes and cells will localize response
- prevent and limits infection/further damage → influx of plasma dilutes toxins, activates plasma protein systems, brings cells that will destroy infectious agents
- prepares injury for healing and repair → dead cells and bacteria products removed
- facilitates development of adaptive immune response (more specific)
- nonspecific
- prevents you from dying!
Steps of inflammation process (vascular response)
(1) vasodilation (increased size of blood vessels) → slower blood velocity; increased blood flow to injured site; plasma-derived mediators involved
(2) increased vascular permeability (platelets) → blood vessels become more porous from endothelial cell contractions; fluid/chemicals leak out (exudation and edema); slower blood flow and increased blood viscosity; increased concentration of RBCs at injury site cause redness (erythema) and warmth
(3) hemostasis: coagualtion/clotting
(4) white blood cell adherence to vessel walls (platelets) & migration through the capillary bed (chemotaxis) → “leukocyte rolling”
(5) leukocyte activation and phagocytosis → secretion/degranulation of compounds
- leukocytes (neutrophils), plasma proteins, other biochemical mediators delivers to injury site → can activate pain fibers → injury, pain, and swelling contribute to loss of function
Describe phagocytosis
- process by which a cell ingests and disposes of foreign material (neutrophils and macrophages)
- cells must leave circulation and migrate to site of inflammation
Steps of phagocytosis
(1) recognition and adherence to target
(2) engulfment (ingestion or endocytosis)
(3) formation of phagosome (cell membrane covered in foreign object)
(4) fusion of phagosome with lysosomal granules
(5) destruction of target
List phagocytes
(1) neutrophils
(2) monocytes and macrophages
Describe neutrophil role in phagocytosis
- first responder
- short life span
- becomes component of pus (what it digested and spit out) → keeps area clean
- removes debris and dead cells
- destroys bacteria
- chemotaxic for monocytes
Describe monocyte and macrophage role in phagocytosis
- monocytes (produced in bone marrow) circulate in blood stream
- migrate to inflammatory site and develop into macrophages after 24 hours (replacing neutrophils)
- long term action → divide and survive longer
- orchestrate wound healing by phagocytizing debris, promoting angiogenesis, releasing cytokines and growth factors, activating fibroblasts, promoting synthesis of collagen
Describe eosinophil role in phagocytosis
- mildly phagocytic
- primary defense against parasites
- help regulate vascular mediators from mast cells
- limit and control inflammation
Describe dendritic cell role in phagocytosis
- link between innate and adaptive immunity through interaction with T lymphocytes
- phagocytic to find out what invader is made of
Which leukocytes participate in the acute inflammatory response?
A - Eosinophils
B - Monocytes
C - Neutrophils
D - All of the above
E - A and C
D - all of the above
What is the correct timeline of inflammatory events?
- Immune Cell infiltration
- Vascular response (hemostasis; vasodilation, increased permeability)
- Immune Cell Activation (degranulation & phagocytosis)
(1) Vascular response (hemostasis; vasodilation, increased permeability)
(2) Immune Cell infiltration
(3) Immune Cell Activation (degranulation & phagocytosis)
Difference between plasma-derived and cell-derived inflammatory mediators
plasma-derived:
- produced in liver
- released into blood stream (float around plasma)
- activated at site of injury (can start inflammatory process)
cell-derived:
- from bone marrow
- in the blood stream (local)
- released at site of injury by cells floating around intravascular compartment to start inflammation
Types of plasma-derived inflammatory mediators
(1) complement system
(2) coagulation (clotting) system
(3) kallikrein-kinnogen system (kinin)
- always around and inactive
- all contain inactive enzymes (proenzymes) that must be converted to be active → once active, can initiate cascade
Role of plasma-derived inflammatory mediators in inflammation
(1) vasodilation/vascular permeability
(2) leukocyte activation, adhesion, and chemotaxis
(3) augmenting phagocytosis
Describe complement system
- activation of C3 and C5 → opsonins, chemotactic factors, anaphylatoxins, cell lysis
- large number of proteins (10% of total serum proteins)
- produces biologically active fragments that recruit phagocytes, activate mast cells, and destroy pathogens
- inactive → active
Pathways of complement system activation
(1) classical (antibody/antigen)
(2) lectin (receptor - PAMP/DAMP)
(3) alternative (spontaneous, pathogenic surfaces)
Describe classical pathway of complement system activation
- primarily activated by antibodies (proteins of acquired immune system)
- antibodies activate C1 → activation of other complement components → activation of C3 and C5 → activate molecules to kill bacteria and activate inflammation
Describe alternative pathway of complement system activation
- activated by substances found on surface of pathogen
- uses unique proteins to form a complex that activates C3 → C5 activation → converges with classical pathway
Describe lectin pathway of complement system activation
- activated by plasma proteins
- binds to bacteria → activate C3 and C5
Functions of C3 and C5 activation
(1) opsonins → mark for phagocytosis
(2) anaphylatoxins → hemostasis: smooth muscle contractions and vasodilation; histamine released from mast cells; enhanced vascular permeability
(3) leukocyte chemotaxis
(4) cell lysis
Describe clotting system
fibrinogen (activated by enzymes from injury) → fibrin (protein that sticks to itself) → clot
- clots plug damaged vessels to stop bleeding, trap microorganisms to prevent spread/infection
- activated by substances released during cell injury and infection and by bacterial products → increase inflammatory response and enhance chemotaxis and vascular permeability
- provides framework for repair and healing → (1) tissue factor (extrinsic - outside damage); (2) contact activation (intrinsic - stressors on endothelial cell that causes damage)
Describe kallikrein-kininogen system (kinin)
- works closely with clotting system
- can be initiated through activation of Hageman factor (factor XII)
- produces bradykinin → molecule responsible for inflammation
Role of primary kininis (bradykinin)
- dilation of blood vessels
- acts with prostaglandins to induce pain
- smooth muscle cell contraction (bleeding)
- increased vascular permeability
Describe cellular-derived inflammatory mediators
- released from cells
- respond to molecules at site of damage and are recruited there
- cell surface receptors bind to molecules and activate intracellular signaling pathways and the cell
Functions of cellular-derived inflammatory mediators
inflammation:
- confine extent of damage
- kill microorganisms
- remove cellular debris
- activate healing/tissue regeneration
Define pattern recognition receptors (PRRs)
- monitor for cellular damage and microorganisms
- recognize: (1) PAMPS → pathogen-associated molecular patterns; (2) DAMPS → damage-associated molecular patterns
Types of PRRs
- toll-like receptors
- c-type lectin receptors
- nucelotide-binding-like receptors
- NOD-like receptors
- complement receptors
- scavenger receptors