First Line of Defense

What is it composed of?  Give Examples.

• External Physical Barriers
• Includes Skin and Mucous Membranes
• AKA Innate Immunity

Second Line of Defense

What is it composed of?

• Protective cells
• Bloodborne chemicals 
• Processes that inactivate or kill invaders

Innate Immunity

Which of the 3 lines of defense is it composed of?

Define it

Why are specific pathogens not able to survive on host?

• Composed of 1st and 2nd lines of defense
• Present at birth prior to contact with infectious agents or their products
• Species specific and due to absence of required receptors or inadequate pH & temperature needed for a pathogen to survive

• Epidermis - Outer layer
• Dermis - deeper layer

Epidermis 

Name different ways it protects against pathogens.

• Multi-layered of tightly packed cells.  Makes it hard for pathogens to penetrate and enter into the body
• Continuous division of cells producing daughter cells.  As daughter cells are pushed toward the surface of the they flatten, die and shed taking any microorganisms present on the surface of the body with them.
• Also contains phagocytic dendritic cells that surround cells and intercept invaders

Dermis

What does it have that makes it difficult for pathogens to penetrate and enter the body?

• Contains tough fibers, collagen, that give skin strength and pliability to prevent jabs and scrapes from penetrating the dermis

• Skin - epidermis and dermis
• Mucous membranes - line lumens of the respiratory, urinary, digestive and reproductive tracts
• Mucus traps foreign substances and destroys them
• Cilia helps move mucus that has trapped substances toward the throat
• Lacrimal apparatus - allows tears to wash across the eye (including glands and ducts)

• Sebum
• Lysozyme
• Gastric juices
• Transferrins
• Microbial antagonism
• Antimicrobial peptides (defensins)

• Oily substance that is composed of fatty acids and inhibits most microbes.  It has a low pH which inhibits bacteria killing them.

HCl, proteases, amylases, lipases that destroy bacter and toxins they produce.

Food can encase bacteria and prevent their destruction.

• Most numerous of formed elements
• They carry oxygen and carbon dioxide in the blood

Differential white blood cell count

What is it?

• Large granules in the cytoplasm that stain different colors depending on the type of granulocyte and dye used.
• Include basophils (blue), neutrophils (red/orange) and eosinophils (Lilac)

• The stain blue with methylene blue
• Can leave the blood but are not phagocytic
• They release inflammatory chemicals (histamines)
• Invovled in allergic response

• Stain a red to orange color with acidic dye eosin
• Phagocytize pathogens 
• Exit the blood through diapedesis
• Defend body against parasitic worms by secreting toxins
• Present in large amounts during allergic reactions

• Stain lilac with a mixture of acidic/basic dyes
• Phagocytize pathogens
• Exit the blood through diapedesis
• AKA polymorphonuclear leukocytes
• Nuclei spereated into 2-5 lobes

• Their cytoplasm appears uniform under a microscope.  But granules can be deteced under an electron microscope.
• Include monocytes (mature into macrophages) and lymphocytes

• Large with slightly lobed nuclei (bean shaped)
• Leave blood and mature into macrophages becoming phagocytic

• Smallest leukocytes, but have large nuclei
• Play a role in immune response
• B, T, NK cells.

• Phagoctyic
• Devour foreign objects (bacteria, fungi, spores, duct, dead cells)
• Wandering macrophages - leave blood to become scavengers
• Fixed macrophages - do not wander and include alveolar macro and microglia of CNS
• Fixed phagocytize in specific organs (heart, BV, lymphatic vessels)

• Primarily helpful for adaptive immunity
• Wait for microbes, phagocytize them and inform adaptive immunity of microbial invasion
• Not WBC's

What are phagocytes?

When does phagocytosis occur?

NAME the 6 steps of phagocytosis.

• Phagocytes - cells of the body capable of phagocytosis
• Occurs when pathogens get past barriers (skin/mucous membranes) of the 1st line of defense
• Chemotaxis, adherence, ingestion, maturation, killing and elimination

• 1st step in phagocytosis
• Movement of a cell toward (positive) a chemical stimulus or away (negative) for a chemical stimulus
• Positive uses pseudopodia to crawl toward microorganisms @ the site of infection
• Injured cells release chemicals that attract phagocytes

• CF - include defensins, peptides derived from complement and chemokines
• C - Chemicals released by leukocytes @ infection site

• When phagocytes arrive at site of infection they bind to microorganisms because of glycoproteins found on the membranes of cells.  

What is opsonization?  

What are opsonins?

Which part of phagocytosis are these part of?

• coating of pathogens with antimicrobial proteins (complement proteins) or specific antimicrobial proteins (antibodies)
• Name for the proteins that coat pathogens
• Part of adherence.

• Phagoctyes extend pseudopodia to surround microbes
• Microbes internalize, pseudopodia fuse to form a food vesicle (phagosome)

• Lysosome adds digestive chemicals to a maturing phagosome the form a phagolysome

• Phagolysomes contain antimicrobial substances like toxic forms of Oxygen, pH of 5.5 as well as 30+ different enzymes attack and destroy engulfed microbes
• Turns the phagolysome into a residual body after breaking down the invader

• Fusion with the plasma membrane and release of contents of residual body

• Eosinophils
• Natural Killer Cells
• Neutrophils

• Secrete antimicrobial chemicals when they attach to helminths' surface
• Gram neg bacterial cell walls trigger eosinophils to secrete mitochodrial DNA forming a physical barrier.  

• Type of lysosome that secrete toxins onto surfaces of virally infected cells and neoplasms
• Non specific b/c they lack receptors that bind to specific antigens
• Work by recognizing the absence of self 

• Enzymes in cytoplasmic membrane add electrons to ovygen creating a radical O₂ and hydrogen peroxide.  These are then converted into hypochlorite killing nearby invaders.  Nitric oxide is then made which induces inflammation
• Another way is by creating NET's.  The netrophil's kill themselves by breaking down their nuclear envelopes and diintegrating the nucleus.  Superoxide and peroxide kill the neutrophil.  NET's are released from the dying cell rupturing cyto. mem.  NET's trap and kill gram pos/neg bacteria

Describe classical pathway.

What is it part of?

• Part of the complement system
• When Antigens bind to antibodies

Describe the alternative pathway.

What is it part of?

• Cytolysis
• Inflammation
• Opsonization

Describe cytolysis.

cell lysis caused by the formation of MAC's (membrane attack complexes).  Holes in the cell cause contents to leak out

coating a cell w/complement which makes phagocytosis more likely to occur.  Opsonins are proteins that increase phagocytosis

• Proteins that are know to affect cells.  They act as a chemical messenger btwn cells.
• Interferons, interleukins and colony-stimulating factors are included in this group.

• Signal production of antiviral proteins (AVP) made by many different cell types that interfere with viral replication but not its attachment
• Host specific, not VIRUS specific
• 3 main types are alpha, beta, gamma
• Some success being used pharaceutically

• Produced by leukocytes
• Act as messengers btwn leukocytes
• Act as costimulators for the immune response
• Increase number of lymphocytes
• Initiate changes in the fuction of lymphocytes

• Stimulate and guide the maturation of a variety of leukocytes

• Complement
• Cytokines
• Fibrinogen

• Chemicals are released due to tissue damage.  Vasodialtion occurs and increases the blood to the damaged area.
• Blood clots form inhibiting the microbe from proliferating
• An abcess forms
• Margination
• Emigration

1. Mast cells
2. Histamines
3. Prostaglandins
4. Leukotrienes

1. Inhibit bacterial growth by denaturing bacterial proteins
2. Increase the effectiveness of interferons
3. Speed up metabolism to increase the rate of tissue repair

Vasoconstriction due to core temperature increase which makes the skin temperature cooler than the core temperature resulting in chills.

• When core temperature decreases and heat loss mechanisms such as sweating kick in.
• Usually means the body is recovering from the fever and returning to normal temperature