Download Lines of Defense - Trinity Christian School

Body Defenses
Specific and Nonspecific Defenses
Non-Specific Defenses
—  Respond immediately to protect the body from
foreign invaders or substances and include
—  The Integumentary System
—  Mucous Membranes
—  The inflammatory response
—  Various proteins produced by body cells
—  Together this system reduces the workload of the
specific defenses
Specific Defenses
—  More commonly called the immune system
—  The immune system is a functional system not an
organ system
—  The functional parts consist of molecules and
trillions of immune cells which circulate in body
fluids and inhabit the lymphatic tissues
—  most important are leucocytes & macrophages
Surface Membrane Barriers
—  Skin
—  Mucous Membranes
Skin
—  Secretes at a pH level which inhibits bacterial
growth
—  Sebum contains chemicals toxic to bacteria
—  Vaginal secretions are also highly acidic
Mucous Membranes
—  Stomach Mucosa – secretes HCl and digestive
enzymes (both kill bacteria)
—  Saliva and lacrimal fluid contain lysozyme
—  Mucous – is sticky and traps microorganism therby
preventing entry
Second Line of Defense
—  Phagocytes
—  Natural Killer Cells
—  The inflammatory Response
—  Pathogen killing chemical substances
—  Tissue repairing chemicals
—  Fever
Phagocytes
—  Includes: macrophages and Neutrophils
—  Are located nearly every body organ
—  Engulf invaders in amoeba fashion
—  Ingest invader into a food vacuole and fuse the
vacuole with a lysosome
Natural Killer Cells
—  NK cells are located in the blood and lymph
—  Are unique in that they can lyse and kill cancer cells and
virus-infected body cells before the immune system
responds
—  Are unlike leukocytes of the immune system
—  Act spontaneously by recognizing certain sugars on the
intruder’s surface
—  NK cells are not phagocytic
—  Release chemicals that attack membranes including the
nuclear envelope
Inflammatory Response
—  Is a non-specific response triggered by injured cells
—  Cardinal signs include: redness, heat, swelling and
pain
—  Injured cells release chemical signals – histamine and
kinins
① 
② 
③ 
④ 
Cause blood vessels to dilate and capillaries to leak
Activate pain receptors
Attract phagocytes and WBCs to the area
Aggregately the above 3 steps are called chemotaxis
Chemotaxis
—  Increases blood flow to the area
—  Swelling and pain restrict movement and force rest
—  The inflammatory response
①  Prevents the spread of damaging agents to nearby
tissues
②  Disposes of cell debris and pathogens
③  Sets the stage for repair
Inflammatory Response
Timeline
1.  Within an hour neutrophils are entering the area
and beginning clean-up of damaged and dead cells
and/or pathogens.
2.  As the inflammatory response continues..
Monocytes follow the neutrophils into the area
3.  Within 8-12 hours the monocytes develop into
macrophages
4.  Macrophages eventually replace the neutrophils
and complete the final disposal of debris
Additional Inflammatory
responses
—  Blood clotting around the area walls it off with fibrin
to prevent the spread of pathogens or harmful
agents
—  Fibrin mesh forms the scaffold for permanent repair
—  Localized heat increase the metabolic rate of tissue
cells in turn speeding up their defensive responses
and repair activities
Third Line of Defense
—  Activated if the pathogen had previously invaded
the body
—  Immune response activates lymphocytes
—  Protective antibodies and T-cells invade the area to
respond with specific action against the invaders
Pus
—  Creamy yellow material formed in an infected
wound
—  Is a mixture of dead or dying neutrophils, broken
down tissue cells, and living and dead pathogens
—  In sites where the inflammatory response cannot
sufficiently clear the area of debris an abscess may
form
—  An abscess is a walled off area of un-drained pus
—  An abscess may have to be surgically drained
Antimicrobial Chemicals
—  Consist of compliment proteins and interferon
—  Compliment proteins circulate in your blood plasma
in an inactive state (20+ types are known to exist)
—  Become attached or fixed to foreign cells, i.e.
bacteria, fungi, foreign RBCs (a compliment fixaton)
—  Compliment proteins are attracted to certain sugars
& foreign proteins (such as antibodies) forming
membrane attack complexes (MAC attack)
MAC Attack
—  The bonding causes lesions in the foreign membrane
—  The lesions allow water to rush into the cell
—  The water infused cell bursts
—  Secondary benefits include:
—  The compliment fixation amplifies the inflammatory
response
—  As the compliment fixation forms chemotaxis
chemicals and vasodilators are released
MAC Attack - continued
—  Chemotaxis attracts neutrophils and macrophages
—  Other chemicals cause the foreign membrane to
become sticky and easier to phagocytize
—  What does MAC stand for?
—  membrane attack complexes
Interferon
—  Virus infected cells release a chemical substance
called interferon
—  The interferons diffuse to nearby cells and bond to
their membrane receptors
—  The bonded receptors hinder virus binding and
subsequent DNA or RNA injection
Fever
—  WBCS and macrophages release pyrogens chemicals
that cause a hormonal response in the hypothalmus
to increase body temperature
—  Fever temperatures cause the spleen and liver to
grab up zinc and iron nutrienrts which bacteria
require to multiply themselves
—  Fever also increases metabolic rate and thereby
repair rates