7.2 HOST-MICROORGANISM INTERACTIONS - HOST RESISTANCE Flashcards
HOST RESISTANCE
Physical Barriers
Macrophages
Physical Barriers
a. Healthy, Intact Skin
b. Cleansing Mechanisms
c. Antimicrobial Substances
d. Indigenous Microbial Flora
e. Phagocytosis
→ primary mechanical barrier to infection
Healthy, Intact Skin
→has substantial numbers of microbial flora that contribute to a low pH, compete for nutrients, and produce bactericidal substances addition
Healthy, Intact Skin
→ ensures that relatively few organisms can survive and prosper in the acid environment
low pH resulting from long-chain fatty acids secreted by sebaceous glands
Spp capable of penetrating normal, healthy skin
Leptospira spp., Francisella tularensis, Treponema spp
Mechanism of urethral opening as a barrier
Stricture
This action allows the urethra to be less susceptible to microorganism growth
urination
Found in the cervical opening that acts as a barrier for microorganism
thick mucus plug
What natural process involves the shedding of the skin surface to remove potential pathogens?
Desquamation
What two antimicrobial components are found in tears?
IgA and lysozyme
How does the respiratory tract help remove trapped microbes?
Mucus traps particles and sweeps them to the oropharynx.
What type of epithelium lines the trachea and aids in clearing particles upward?
Ciliated epithelium
Which reflex helps expel potentially infected agents from the respiratory system?
Cough-sneeze reflex
What two mechanisms in the gastrointestinal tract prevent organisms from attaching to the intestinal epithelium?
Mucous secretions and peristalsis
What cleansing action in the genitourinary tract helps prevent infection?
Voiding urine
What characteristic of the vagina inhibits colonization by transient organisms?
Acidity
Cleansing Mechanisms of the body
Desquamation
IgA and lysozyme in tears
Mucus in RT
Ciliated epithelium in trachea
Cough-sneeze reflex
Mucous secretions and peristalsis of the GI tract
Voiding urine
Acidity of vagina
Antimicrobial Substances
Lysozyme
Secretory IgA
β-lysins
Interferon
→low-molecular-weight (approximately 20,000 D) enzyme that hydrolyzes the peptidoglycan layer of bacterial cell walls
Lysozyme
Lysozyme found in
serum,
tissue fluids,
tears,
breast milk,
saliva, and
sweat
→serve as opsonins, fix complement and neutralize the infecting
organism
Secretory IgA
Secretory IgA →found in
mucous secretions of the
respiratory,
genital, and
digestive tracts
Secretory IgA serve as
opsonins
→low-molecular-weight cationic proteins in serum
→lethal against gram-positive bacteria and are released from platelets during coagulation
β-lysins
→inhibits proliferation of viruses
Interferon
→compete with pathogens for nutrients and space
Indigenous Microbial Flora
→substances that inhibit the growth of closely related bacteria
Bacteriocins
→process by which phagocytes engulf and dispose of microorganisms and cell debris
Phagocytosis
necessary for the killing and digestion of the engulfed particles
Lysosomes
Lysosomes [enumerate]
myeloperoxidase,
proteases,
cathepsin,
lactoferrin,
lysozyme, and
elastase
→has receptors on the cell membrane for some complement components that stimulate cell motion, the metabolic burst, and secretion of the lysosome contents into a phagosome
PMN - polymorphonuclear leukocyte
PMN circulating half life hours
2-7
PMN may migrate to the tissues where their half life is
less than a week
→circulate as monocytes for 1 to 2 days and then migrate through the blood vessel walls into the tissues and reside in specific tissues as part of the MONONUCLEAR PHAGOCYTE SYSTEM
Macrophages
Macrophages are part of the [system]
MONONUCLEAR PHAGOCYTE SYSTEM
→widely distributed in the body and play a central role in specific immunity and nonspecific phagocytosis
Macrophages
Chemotaxis two types
Diapedesis
Chemotaxis
→ movement of the neutrophils between the endothelial cells of the blood vessels into the tissues
DIAPEDESIS
→directed migration of PMNs into the area of infection
CHEMOTAXIS
→facilitated by the binding of specific antibodies to the microorganism
Attachment
→coating of the bacterium with antibody or complement components results in enhanced phagocytosis by the PMN
OPSONIZATION
Neutrophils have membrane receptors for?
Fc region of
IgG1
IgG3
C3b component of complement
Which antibody classes can bind to organisms to initiate opsonization?
IgG1 or IgG3
What happens when the antibody response is insufficient for opsonization?
Complement is fixed on the surface of the organism
Which pathway can be activated by endotoxins or polysaccharides for opsonization?
Alternative complement pathway
✓Cell membrane of the phagocytic cell invaginates and surrounds the attached particle
Ingestion
In Ingestion ✓Particle is taken into the cytoplasm and enclosed within a
vacuole called a
PHAGOSOME
✓Phagosome fuses with lysosomes
PHAGOLYSOSOME
Lysosomes release their contents into the phagosome
DEGRANULATION
Ingestion included enzymes
proteases,
lipases,
RNase,
DNase,
peroxidase, and
acid phosphatase
→phagocytosis of a particle triggers a significant increase in the metabolic activity of the neutrophil or macrophage
Metabolic or Respiratory Burst
Killing / Metabolic or Respiratory Burst increases in
glycolysis
→body’s response to injury or foreign
body
Inflammation
→hallmark of inflammation:
accumulation of large numbers of
phagocytic cells
→leukocytes release mediators or
cause other cell types to release which cause ______________ as a result of greater blood flow, edema from an increase in vascular permeability, and
continued phagocyte accumulation,
resulting in ____________
erythema
pus
CARDINAL SIGNS OF INFLAMMATION
SWELLING, tumor
REDNESS, rubor
HEAT, calor
PAIN, dolor
LOS OF FUNCTION
Chemical Mediatiors of Inflammation:
✓Histamine
✓Kinins
✓Leukotrienes
✓Prostaglandins
✓Acute phase reactants
✓Cytokines
✓Acute phase reactants examples
CRP,
Serum amyloid A,
antitrypsin,
fibrinogen
✓Cytokines that mediate inflammation
IL-1,
IL-6,
TNF-α,
IFN-γ,
IL-2
