C15 Flashcards
Ways in which the body protects itself from
pathogens—referred to as three lines of defense.
Host defense mechanism
are general and serve to protect the body against many harmful substances.
Ex. Innate or inborn
Nonspecific host defense mechanisms
In addition to the skin as a. physical barrier, there are other factors (e.g., pH and temperature of skin, perspiration, cilia, and various enzymes in secretions such
as lysozyme) that are components of the first line of defense.
Cellular and chemical factors
When indigenous microbiota prevent colonization of “new arrivals” as a result of competition for sites and nutrients
and production of lethal substances
Microbial antagonism
Levels of this glycoprotein increase in response to systemic bacterial infections; it binds to iron depriving pathogens of this vital nutrient.
Transferrin
Stimulated by pyrogenic (fever-producing)
substances (e.g., pathogens and interleukin
Fever
These are small antiviral proteins produced by virus-infected cells; they prevent viruses from multiplying.
Interferons
Three types of interferron
Alpha gamma beta ( produced by three different types of cell)
Interferons are not virus-specific, but they are
species-specific.
is a process by which phagocytosis is
facilitated by the deposition of opsonins (e.g., antibodies or certain complement fragments) onto objects (e.g., pathogens).
Opsonization
Complement components interact with each other in a stepwise manner known as the
Complement cascade
Plasma proteins that increase rapidly in response to infection, inflammation, or tissue injury; (e.g., is C-reactive protein).
Acute phase protein
These are chemical mediators released from many different types of cells in the body; they enable cells to communicate with each other—within the immune system and between the immune system and other systems of the body.
Cytokines
The body responds to any local injury, irritation, microbial invasion, or bacterial toxin by a complex series of events referred to as
inflammation;
The primary purposes of the inflammatory response are to
– Localize an infection
– Prevent the spread of microbial invaders
– Neutralize any toxins being produced at the site
– Aid in the repair of damaged tissue
The four major signs and symptoms of inflammation are
redness, heat, swelling (edema), and pain.
Plasma that escapes from the capillaries into the site causes the area to become
Edematoud (swollen)
Sequence of Events in Inflammation
- Tissue injury
- Vasodilation
- Increased permeability
- Emigration of leukocytes
- Chemotaxis
- Phagocytosis
The accumulation of fluid, cells, and cellular debris at the inflammation site is known as an
inflammatory exudate.
The most important groups of phagocytes in the human body are
macrophages and neutrophils.
If the exudate is thick and greenish-yellow,
containing many live and dead leukocytes, it is
known as a
purulent exudate or pus.
The three types of granulocytes are
eosinophils, basophils, and neutrophils.
an abnormally low number of circulating
leukocytes
Leukopenia
initially serve to protect the organism from
phagocytosis (i.e., they serve an antiphagocytic function).
Capsules
Some bacteria produce an exoenzyme called
leukocidin,
which kills phagocytes.
Disorders and conditions affecting leukocyte motility and chemotaxis
Inability of leukocytes to migrate in response to chemotactic agents may be related to a defect in the production of actin, a structural protein associated with motility.
Additional Factors That Can Impair Host
Defense Mechanisms
- Nutritional status
- Increased iron levels
- Stress
- Cancer and cancer
chemotherapy - Various genetic defects
- Age
- AIDS
- Drugs (e.g., steroids)
