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
