Microbiology Chapter 15

What are our three main lines of defense?

• first line of defense

• second line of defense

• third line of defense

Which are non specific lines of defense? Why?

first and second because they target any type of microorganisms

Which are specific lines of defense? Why?

third because the antibody can only act on specific pathogens

What is the interrelationship between the defense mechanism?

The body’s defense mechanisms work together as a layered system: external barriers prevent pathogens from entering, internal nonspecific defenses attack any invader that gets inside, and specific acquired immunity provides targeted, long-term protection. All parts operate together to keep the body safe from infection.

What composed the first line of defense?

• normal microbiota

• skin

• mucus membranes

• chemicals

• processes

What is the importance of normal microbiota?

• prevent attachment of invaders

• deplete essential nutrients (cause pathogens not to grow)

• produce antimicrobial substances

What characteristics of skin and mucus membranes prevent entry of microorganisms?

• salty skin

• acidic skin

• layer of cells that are tightly packed

• the constant shedding of cells

• normal microbiota

• moist secretions such as tears

What makes the skin acidic?

the body produces oil, and the oil has fatty acids which stay on the skin to make it acidic

What makes the skin salty?

When the body produces sweat, the water evaporates leaving the salt on the skin to make it salty

What are characteristics of skin?

• thicker with many tightly packed cell layers

• has an outer layer of dead cells and inner layer of living cells

• no mucus present

• dry in water content

• has defensins, lysozyme, and sebum

• has no cilia present

• constantly sheds and replaces cells

What are characteristics of mucous membranes?

• thinner with few tightly packed cell layers

• has living cells

• mucus present

• moist in water content

• has defensins and lysozyme in some mucous membranes

• has no sebum present

• cilia present in trachea and uterine tubes

• constantly sheds and replaces cells

What are some chemicals present in the skin that are antimicrobial?

• salt, lysozymes (sweat, tears, saliva)

• fatty acid (sebum)

• antimicrobial peptides (defensins and dermcidin)

What are other antimicrobial substances included in the first line of defense?

• HCl, bile salts, enzymes (gastric juices)

• lactic acid (vaginal secretions)

What activities or processes belong in the first line of defense?

• peristalsis

• defecation

• vomiting

• menstrual flow

• coagulation

What are the components of the second line of defense?

• phagocytosis

• extracellular killing by leukocytes

• nonspecific chemical defenses

• inflammation

• fever

What are the different kinds of WBC?

• neutrophiles

• eosinophils

• basophils

• lymphocytes

• monocytes

Where are WBC formed?

in the red bone marrow

What WBCs are involved in phagocytosis?

neutrophils and eosinophils

What WBCs are involved in inflammation?

basophils

What WBC get out of the blood and become phagocytes in the tissue?

monocytes

What WBCs are involved in adaptive immunity?

lymphocytes

How do different WBC differ from one another?

• neutrophils - stained by basic and acidic dyes and have granules in the cytosol 

• basophils - stained by basic dyes and have granules in the cytosol

• eosinophils - stained by acidic dyes and have granules in the cytosol  

• lymphocytes - have no granules

• monocytes - have no granules

What are the steps of phagocytosis?

• chemotaxis of phagocytes to microbes

• adhesion - attach to microorganism

• ingestion of microbes by phagocytes (vacuum)

• fusion of a series of vesicles, including lysosomes(have digestive enzymes and will fuse with phagosome)

• killing of microbes by enzymes and other chemicals 

• eliminations - exocytosis

What are some phagocytes in the human body that are found in the lungs?

alveolar macrophages

What are some phagocytes in the human body that are found in the brain?

microglial cells

What are some phagocytes in the human body that are found in the skin?

dendritic cells

What are some phagocytes in the human body that are found in the liver?

Kupffer cells 

What are the types of cells that kill extracellularly?

• eosinophils

• natural killer lymphocytes (NK cells)

• neutrophils

What cells mainly attack parasitic helminths?

eosinophils

What cells secrete toxins onto the surface of virally infected cells and tumors?

natural killer lymphocytes (NK cells)

What is eosinophilia?

abnormally high number of eosinophils in the blood or tissues

What are the proteins involved in the second line of defense?

• TLRs and NODs

• interferons

• complement system

What are TLRs?

toll like receptors are integral proteins of the cytoplasmic membranes of phagocytic cells 

What are NODs?

nod like receptors are proteins in the cytosol of phagocytic cells

How do TLRs assist phagocytic cells?

they recognize PAMPs of pathogens and trigger apoptosis of pathogens

How do NODs assist phagocytic cells?

they recognize PAMPs of pathogens and trigger apoptosis of pathogens

What are the defensive responses of TLR?

activate inflammatory and antimicrobial responses that help destroy pathogens 

What are the defensive responses of NOD?

detect intracellular pathogens, trigger inflammation via cytokines, promote antimicrobial killing, activate inflammasomes, and help coordinate adaptive immunity

What are interferons?

protein molecules

What is the action of interferons?

inhibit the spread of viral infections

What are the three classes of interferons?

• alpha

• gamma

• beta

What cells produce alpha interferons?

leukocytes and cells of the epithelium

What cells produce beta interferons?

fibroblasts

What cells produce gamma interferons?

activated T lymphocytes and NK lymphocytes

How do interferons inhibit the spread of viral infections?

• alpha and beta interferons inhibit by stimulating the production of antiviral proteins

• gamma interferons inhibit by stimulating phagocytic activity of macrophages and neutrophiles  

What is a complement system?

set of serum proteins designated numerically according to the order of their discovery

What are the actions of the complement system?

• stimulates opsonization

• stimulates inflammation

• causes lysis of the pathogens 

What are the three pathways to activate the complement system?

• classical pathway

• alternative pathway

• lectin pathway

What happens after complement system 1 (C1) is activated?

• C1 splits molecules of C2 and of C4

• Fragments of C2 and C4 combine to form a second enzyme that splits C3 into C3a and C3b

• C3b combines with the second enzyme to form a third enzyme

• Third enzyme cleaves C5 into C5a and C5b

• C5b combines with C6, C7, C8, and several molecules of C9 to form a membrane attack in the pathogen’s cytoplasmic membrane, leading to lysis of the cell

What is a MAC?

membrane attack comples

What does MAC do?

drills a circular hole in the pathogen’s cytoplasmic membrane, leading to lysis of the cell

What is inflammation?

a response to tissue damage resulting from various causes

What are the signs and symptoms of inflammation?

• redness

• heat

• swelling

• pain

what is acute inflammation?

• short period

• More beneficial

• Appears rapidly

• Causes less damage to tissues

what is chronic inflammation?

• last longer

• Causes more damage

what happens to the diameter of blood vessels and permeability of blood vessels during inflammation?

• blood vessels dilate with inflammation

• Permeability increases with inflammation

What happens when blood vessels become permeable?

• leakage of fluid causing edema and pain

• Delivered antimicrobial chemicals to site

• Migration of phagocytes

what produces bradykinin?

Injured tissues produce causing the dilation of blood vessels leading to increased blood flow

what produces prostaglandins?

Injured tissues produce causing blood vessels to be more permeable

what produces leukotrienes?

Macrophages releases with injured tissues causing blood vessels to be more permeable

What caused the redness and increase in temperature?

Bradykinin and histamines causing the dilation of blood vessels leading to increased blood flow

What caused the edema and pain of the inflamed area?

Bradykinin, prostaglandins, leukotrienes, and histamines making blood vessels more permeable leading to the leakage of fluid causing edema. The excessive amounts of fluid cause pressure on nerve endings leading to pain

Discuss the process of inflammation

• Recognition of microbes/damage

• Mediators released (histamine, cytokines, prostaglandins)

• Vasodilation + ↑ permeability → redness, heat, swelling

• Leukocyte recruitment (neutrophils → macrophages)

• Elimination of microbes/debris

• Resolution or chronic inflammation

What chemicals are involved in inflammation?

Histamines, serotonin, bradykinin, and prostaglandins

What is fever?

a body temperature over 37^oC or 98.6oF

What are pyrogens?

Fever producing/enhancing chemicals

What are types of pyrogens?

• bacterial toxins

• cytoplasmic contents of bacteria released by lysis

• antibody antigen complexes 

• interleukin-I

How is fever formed?

• chemicals secreted by phagocytes travel in blood to hypothalamus (pyrogens must be present)

• Hypothalamus secretes prostaglandin (will resets hypothalamic thermostat)

• Nerve impulses cause shivering, higher metabolic rate, inhibition of seating, and vasoconstriction

• These processes increase body temperature to the point set by the hypothalamic thermostat

What are the benefits of fever?

• enhances the effects of interferons

• inhibits growth of some microorganisms

• may enhance the performance of phagocytes

What causes vasodilation?

Inflammatory chemicals