immune i Flashcards
Immunity definition
2 systems within immune system
-resistance to disease
Innate and adaptive defense systems
Innate defense first line of defense
External body membranes (skin and mucosae and their secretions)
- ward off pathogens
- physical barrier to most microbes
- keratin resistant to weak acids and bases, bacterial enzymes, and toxins
- mucosae provides similar barriers
protective chems that inhibit or destroy microbes as part of the innate immune system’s 1st line of defense
- acidity of skin and secretions (acid mantle) –> inhibits growth
- enzymes (lysozyme of saliva, respiratory mucus, and lacrimal fluid) –> kills microbes
- Defensins (antimicrobial peptides) –> inhibit growth
- other toxic chems (lipids in sebum, dermcidin in sweat)
innate immune system
- respiratory part
- how to breach
- expulsion
- respiratory system has mucus coated hairs in nose –> also, cilia of upper respiratory tract sweep dust and bacteria mucus towards mouth
- nicks and cuts
- vomiting, shedding epithelial cells, peeing, pooping
Innate immune 2nd line of defense
- when is it necessary
- what does it include
-necessary if microbes invade deeper tissues
Includes
- cells (phagocytes and NK cells)
- Antimicrobial substances (interferons, complement proteins, and antimicrobial proteins)
- fever
- inflammatory response (macrophages, mast cells, WBCs, inflammatory chems)
Innate immune: 2nd line of defense: Phagocyte examples
Neutrophils = most abundant but dies fighting –> become phagocytic on exposure to infection material
Macrophages = main, robust, phagocytic cells developed from monocytes –> free macrophages wander tissue spaces –> fixed macrophages live in organs
-alveolar macrophages = free
-stellate macrophages = fixed in liver
microglia = fixed in brain
Innate immune: 2nd line of defense: Phagocyte function
adheres to particle, but sometimes this is difficult –> opsonization marks pathogens by coating them with complement proteins or antibodies which makes them easy to eat
- ctoplasmic extensions bind to and engulf particle in vesicle called phagosome
- phagosome fuses with lysosome = phagolysosome
Innate immune: 2nd line of defense: Phagocyte mobilization
Neutrophils lead and macrophages follow
-as this continues, monocytes arrive –> 12 hrs after they leave blood/enter tissue, they become macrophages –> replace dying neutrophils and stick around for clean up and repair
If there’s inflammation due to pathogens, complement is activated and adaptive immunity elements arrive
Steps for phagocytic mobilization
- Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-inducing factors from injured cells
- Margination: neutrophils cling to walls of capillaries in inflamed area in response to CAMs
- Diapedesis or emigration of neutrophils
- Chemotaxis: inflammatory chems (chemotactic agent) promote positive chemotaxis of neutrophils
Natural killer cells
- Nonphagocytic large granular lymphocytes
- attack cells w/o “self” cell-surface receptors
- induce apoptosis in cancer and virus-infected cells
- secrete potent chems that enhance inflammatory response
chems released by NKs
Perforin: forms transmembrane pore
Granzymes enter pore and cause apoptosis
Antimicrobial substances (2nd line of defence)
- examples
- possible functions
- interferons and complement proteins
- some attack microbes directly; others hinder microbes’ ability to reproduce
Interferons
- family of immune modulating proteins each with slightly dif effects
- viral-infected cells secrete IFNs to warn neighboring cells
- IFs enter neighboring cells and produce prots that block viral reproduction and degrade viral RNA
- Artificial IFNs used to treat hepatitis C, genital warts, multiple sclerosis, hairy cell leukemia
IFN alpha and beta special skill
-activate NK cells –> indirectly fight cancer
IFN gamma
“immune interferon”
- secreted by lymphocytes
- widespread immune mobilizing effects
- activates macrophages
Summary: 3 main actions of IFNs
- warn neighboring cells (causing the production of antiviral proteins)
- activate macrophages
- activate NK cells
Complement system
- 20 blood proteins that circulate in inactive form
- C1-C9; factors B, D, and P; and regulatory proteins
- major mechanism for destroying foreign substances
- our cells have complement activation inhibitors
How to complements work?
- unleash inflammatory chems that amplify all aspects of inflammatory response
- kills bacteria and certain other cell types by lysis
- enhances both innate and adaptive defenses
Classical pathway of complement activation
- antibodies bind to invading organisms and to complement components
- called complement fixation
- first step in activation
lectin pathway of complement activation
- lectins are produced by innate system to recognize foreign invadors
- when bound to foreign invaders, can also bind and activate complement
Alternative pathway of complement activation
-activated spontaneously , lack of inhibitors on microbes’ surface allows process to proceed
Similarities between the three complement activation pathways
- each involves activation of proteins in orderly sequence
- each step catalyzes the next
- each pathway converges on C3 which cleaves into C3a and C3b
-Common terminal pathway initiated that enhances inflamation, promotes phagocytosis via opsonizations, and causes cell lysis (MAC)
Actions of C3b and C3a
Cell lysis begins when Cb binds to target cell –> insertion of complement proteins called membrane attack complex (MAC) into cell’s membrane –> MAC forms and stabilizes hole in membrane –> influx of water –> lysis of cell
-C3b also causes opsonization
C3a and other cleavage products amplify inflammation –> stimulate mast cells and basophils to release histamine –> attract neutrophils and other inflammatory cells
Inflammatory response
- triggered whenever body tissues injured
- prevents spread of damaging agents
- disposes of cell debris and pathogens
- alerts adaptive immune system
- sets the stage for repair
