Nonspecific Host Defenses (BE #3) Flashcards
Describe difference between nonspecific & specific defenses. Where are 1st, 2nd & 3rd line defenses found?
Nonspecific - general defense response; response is the same every time no matter what species of pathogen; includes 1st & 2nd line)
Specific - includes specific immune responses.
Why are nonspecific defenses described as “innate?”
They are present at birth prior to contact with infectious agents or their products.
The body’s first line of defense occurs at body ______.
surfaces
Name 5 nonspecific defenses involving the skin or mucous membranes.
- keratin in outer epidermal layers make skin dry
- fatty acids in sebum make skin acidic
- salty perspiration makes skin hypertonic
- HCl in stomach
- sloughing of epidermal cells reduces bacterial numbers
Name 3 places in the body where acidic environments serve as a chemical defense.
- stomach (HCl)
- fatty acids in sebum in skin
- acidic environment of vagina
Tears, perspiration & saliva contain _________, an enzyme that destroys the bacterial cell wall. This enzyme is effective against ________ bacteria b/c they lack an ________ ________.
lysozyme
G(+)
outer membrane
If urine is not considered microbiocidal, how can it serve as a mechanical defense?
This defense is mechanical - the movement of urine through the urinary tract dislodges bacteria & transports them out of the body.
Describe why peristalsis in the digestive tract is considered a mechanical defense.
Moves the bacteria out of the body.
Explain the action of the “ciliary escalator” (mucociliary response).
Mucous traps bacteria, dust, etc. and cilia moves the mucous up the respiratory tract where it is coughed up and swallowed, going down the esophagus and into the HCl of the stomach.
Why are prepubertal & postmenopausal women at an increased risk for yeast infections?
Low estrogen means increased ph level in the vagina. The low pH level (acidic) is what keeps the bacteria (Candida albicans) at bay.
How do normal flora provide defense against pathogenic bacterial species? Explain microbial antagonism.
Normal flora produce substances that are harmful to pathogens & alter conditions that affect survival of pathogens.
transferrins
- iron binding compound in blood
- inhibit bacterial growth by making less iron available to the bacteria
- excess iron “overloads’ the transferring, making iron available for microbial growth
fatty acids
- contained in oil secreted by skin sebaceous glands & make the skin slightly acidic
bile
- produced by the liver
- passed in feces
- E. coli is resistant to bile
lysozyme
- an enzyme that destroys the bacterial cell wall, especially on G(+) bacteria
- found in tears, saliva & perspiration
salt
- contained in perspiration
- creates a hypertonic environment
Name a bacterial species that normally inhabits the human colon & is resistant to bile.
Esherichia coli
Enterococcus faecalis
When used in media, what bacteria does bile select for? Against?
selects for G(-)
selects agains G(+)
What is meant by a body’s “second line of defense?”
General defenses that occur if pathogens get past surface defenses.
What are the 5 types of white blood cells (called leukocytes)?
- macrophages
- eosinophils
- neutrophils
- basophils
- lymphocytes
- release histamine;
- are involved in the inflammatory & allergic responses
- granulated cells
basophils (white blood cell)
- major phagocyte
- some are fixed (liver, skin, lungs, etc,); some are wandering
- some called dendritic cells
- involved in antigen presentation
macrophages (WBC)
- major phagocyte
- active during parasitic infections, such as helminths (worms)
eosinophils
- major phagocyte
- extremely active during the initial phases of an infection
neutrophil
- 3 types: B cells T cells NK cells - all are involved in specific immune responses - NK are nonspecific
lymphocytes
mast cells
- found in almost all tissues
- most abundant in skin & GI tract
- contain large amounts of histamine
- remain in tissues & don’t circulate
- are derived from bone marrow
How are Natural Killer cells and T cells similar?
How are they different?
They both produce perforins.
T-cells are specific (they have surface complex receptors that bind to specific Antigen-MHC complexes).
NK cells lack these receptors.
T cells are involved in specific immune responses; NK are involved in 2nd line nonspecific defenses.
What is the function of perforins?
They perforate (punch holes) in the cell membrane/cell envelope of pathogen infected host cells or bacterial cells.
List the 4 stages of phagocytosis.
CAID
- Chemotaxis
- Adherence/attachment
- Ingestion
- Digestion
Chemotaxis
- the chemical attraction of phagocytes to a particular location
- chemotactic chemicals attract phagocytes include:
bacterial toxins
components of damaged tissue cells
complement proteins
antibodies
Adherence/attachment
- b/c adherence to pathogen may be difficult (M proteins, slippery capsules), the phagocytes coat the surface of the with complement proteins & antibody proteins to facilitate phagocytosis (process is called OPSONIZATION). Coating is called opsonin.
Ingestion (in phagocytosis)
- phagocyte engulfs the microbe with its plasma membrane. The plasma membrane surrounds the microbe & pinches off around the microbe, forming a vesicle.
Digestion (in phagocytosis)
The microbe containing vesicle fuses with a lysosome (contains digestive enzymes). After digestion, microorganism is expelled by exocytosis.
Example of a bacteria that resists phagocytosis. Why?
Mycobacterium tuberculosis
They have a thick, waxy capsule that resists it.
If a bacterium has a slippery, slimy outer capsule, how can a phagocyte get it?
Coat it with opsonin (process called opsonization).
Name 2 opsonins.
- complement protein (nonspecific)
- antibody (specific)
What event triggers the hypothalamus to reset the body’s temperature?
phagocytosis
What compound is involved in resetting the hypothalamus at a higher temp?
interleukins cause the release of prostaglandins which reset the hypothalamus.
What mechanisms in the body can increase body temperature? (what does the body do to warm up?)
- shivering
- vasoconstriction of blood vessels to skin & limbs
- goose bumps
Why are low grade fevers beneficial?
HEAT
- inhibits growth of some microbes
- increases heart rate so WBC are delivered to infection sites more rapidly
- increases B & T cell division
- speeds up chemical reaction rates
- decreases the effects of endotoxins
Why are high-grade fevers harmful?
start to denature your body’s own proteins/enzymes
What is the action of fever reducers/pain relievers such as ibuprofen & acetaminophen?
Inhibit synthesis of prostaglandins so hypothalamus doesn’t raise body temp.
Why is it not a good idea to administer a fever reducer for a low-grade fever?
- makes kids feel better - they play & don’t rest
- reduced fever allows pathogen to multiply again
What does NET stand for?
neutrophil extracellular traps
Explain how neutrophils (a forms of leukocyte) commit suicide to form NETS.
Once triggered, the cells release the contents of their nuclei. The nucleic acid, mixed with bactericidal enzymes, form a lethal network outside the cell. Pathogens get caught & killed in the NET.
What compound, produced by viral-infected cells, serves as a red flag or warning to other cells to produce antiviral compounds?
interferons
Interferons are synthesized in the lab using _________ .
recombinant DNA techniques (bacteria make the interferons)
They ARE host specific
They ARE NOT virus specific
What viral diseases are being treated with interferons?
Hepatitis B & C
Kaposi’s sarcoma (AIDS patients)
herpes
multiple sclerosis
What activates the complement system? Name the 2 pathways.
Classical pathway - activated when antibody binds to antigen (complement is fixed & activated)
Alternate pathway - activated by polysaccharides in bacterial capsules
What are the 4 functions of the complement system?
COLA
- Chemotaxis
- Opsonization
- Lysis
- Activation of inflammatory response
What forms membrane attack complexes (MAC) and what is their function?
Complement proteins - punch holes in the cell envelope of bacteria to cause lysis.
Explain the activation of the inflammatory response.
Activated by complement proteins. Basophils & mast cells release histamine, which causes vasodilation & increased permeability of blood vessels.
What are the 4 major symptoms of the inflammatory response? Explain what causes each of these symptoms.
- redness - increased blood flow to the area (from vasodilation of blood vessels)
- warmth (heat) - from increased chemical reactions in area
- swelling - from more fluid leaving blood vessels (they become leaky)
- pain/irritation - from swelling, from toxins produced by bacteria, from prostaglandin release
Blood vessels dilate & become “leaky” due to the release of ______ by _____ and _________. This chemical causes blood vessels to _________ and become ________.
histamine basophils mast cells dilate permeable
What compound is released from injured cells to effect pain receptors?
prostaglandins
Why do medications like acetaminophen reduce both fever and pain?
they inhibit prostaglandin synthesis/release, which are involved both in fever & pain mechanisms.
What is pus?
dead phagocytes & damaged tissue
What component of blood is involved in the clotting mechanism? Why is this important in ridding the body of a particular pathogen?
platelets
It walls off the pathogen, containing it so it cannot invade other tissues.
