Chapter 16-Exam 3 Flashcards
able to be productively infected
susceptibility
unable to allow a productive infection
resistance
an active process that prevents establishment or progression of an infection
immunity
defenses against any pathogen, present at birth
innate immunity
First line of defense in the immune system
physical and chemical factors & normal microbiota:
- intact skin
- mucous membrane and their secretions
- lacrimal apparatus
- ciliary escalator
- epiglottis
- saliva
- urine
- vaginal secretions
- peristalsis, defecation, vomiting
- normal microbiota
Second line of defense in the immune system
non-specific physiologic processes:
- phagocytes such as neutrophils, eosinophils, dendritic cells, and macrophages
- inflammation
- fever
- antimicrobial substances
Third line of defense in the immune system
adaptive immunity:
- specialized B and T cells (lymphocytes)
- antibodies
specific resistance to a specific pathogen, develops overtime
adaptive immunity
physical factors of innate immunity that: block
skin, mucous membrane, epiglottis
physical factors of innate immunity that: trap
mucus, hairs
physical factors of innate immunity that: wash
tears, saliva, urine, vaginal secretions
physical factors of innate immunity that: move
cilia, peristalsis, defecation, vomiting
cutaneous membrane
skin: covers the body surface and provides a physical barrier to the entrance of microbes
mucous membranes
line the body cavities and are open to the exterior of the body
Epidermis
consists of tightly packed cells with a thick layer of keratin- containing dead cells
_________ inhibits microbes (Epidermis)
dryness
_________ blocks microbes (Epidermis)
water-tightness
_________ removes microbes (Epidermis)
shedding
inner layer of skin that is made of connective tissue
dermis
______ ________ are in the dermis
blood vessels
Why can microbes get into the blood stream if they are found in the dermis?
Endothelial cells of vessels are not densely packed, and can allow microbes to pass by them
What is the purpose of the keratinized layer in the epithelium?
to provide an air-tight barrier
How do mucous membranes differ from cutaneous membranes?
They do not have a water- tight keratinized layer above the living cells and instead of having squamous epithelium, they have goblet cells that produce mucous that protects the epidermis.
What systems do the mucus membranes line?
mucus membranes are an epithelial layer lining the respiratory, gastrointestinal, urogenital, visual, and auditory
systems.
traps microbes in respiratory and GI tracts
mucus
What components make up mucus?
a mix of glycoproteins and water
contains many anti-microbial substances
surface projections on cells of the respiratory
tract that move mucus and trapped microbes out of the
upper respiratory tract.
cilia
Which is more effective: mucus membranes or the skin?
skin
What is the ciliary escalator, and how far does it move the ciliary blanket? What can speed it up?
The ciliary escalator is also known as ciliary clearance and it is the self-clearing mechanism of the bronchi.
ciliary escalator moves the mucus blanket 1-3 cm/hr
coughing speeds up the movement
What pathway does tear flow take?
Tears flow from lacrimal glands under eyelid to
lacrimal canal
_________ and _________ by tears keeps microbes from settling on eye surface
washing; dilution
chemical factors that are part of the first line of defense
- sebum
- lysozyme
- saliva
- gastric juice
- urine
- vaginal secretions
What is sebum? What is it made out of?
Sebum is the oily secretion of the
sebaceous glands that are embedded in the skin. Sebum is a complex mixture of lipids (many fatty
acids and triglycerides) that have anti-microbial
activity.
______ and ______ also contain many nutrients that bacteria and fungi may use to grow
sweat and sebum
what pH inhibits bacteria and fungi?
pH of 6 or lower
pH 1.2–3.0
gastric juice (hydrochloric acid)
pH (3–5)
vaginal secretions and skin
a substance made by saliva or urine that acts as a bacteriostatic or bactericidal for many species
urea
What is a lysozyme? Who discovered it?
Lysozyme is a small enzyme that attacks the peptidoglycan chains in the cell walls of bacteria, causing the cells to burst. Alexander Flemming (who discovered
penicillin) discovered lysozyme as an antibiotic.
What are Hematopoeitic cells and what do they function as in the second line of defense?
perform a variety of functions
- red blood cells carry O2 and CO2
- white blood cells function in immunity and injury
travel throughout the body via the circulation
move in and out of the interstitial space (fluid
surrounding all cells of the body) by squeezing
through the endothelial cells of the blood vessels
all develop from a common stem cell
three types of granulocytes
- neutrophils
- basophils
- eosinophils
three types of agraunulocytes
- monocytes (macrophages)
- dendritic cells
another term for WBCs
leukocytes
key features of neutrophils
phagocytosis
key features of basophils
histamine
key features of eosinophils
kill parasites
key features of monocytes
phagocytosis (APC)
key features of dendritic cells
phagocytosis (APC)
three types of lymphocytes
- T cells
- B cells
- NK cells
key features of T cells
cell-mediated immunity
key features of B cells
produce antibodies
key features of NK cells
destroy target cells (infected or cancerous)
non WBCs that are involved in blood clotting
platelets
Differential White Cell Count (what are the percentages of each?)
Neutrophils 60–70% Basophils 0.5–1% Eosinophils 2–4% Monocytes 3–8% Lymphocytes 20–25%
what is the difference between leukocytosis and leukopenia?
increase in white cell count = leukocytosis
decrease in white cell count = leukopenia
describe the pathway of lymph flow throughout the lymphatic system?
blood plasma —> interstitial fluid —> lymph —> blood plasma
what type of phagocytic cells live only a short time
and predominate early in infections?
neutrophils
what type of phagocytic cells last up to several months
and predominate later in infections?
macrophages and other wandering phagocytes
Describe the seven phases of phagocytosis:
- chemotaxis and adherence of pseudopod
- ingestion of target
- formation of phagocytic vesicle or phagosome
- fusion with a lysosome, forming phagolysosome
- digestion of target by digestive enzymes
- formation of residual body
- discharge of indigestible material
Define Toll-like receptors
TLRs are protein molecules on cell surfaces
throughout the body
TLRs are how macrophage pseudopods adhere to
bacteria
TLRs are “pattern recognition receptors,” that is,
they recognize pathogen-associated molecular
patterns, specific signatures in molecules in the
extracellular space.
TLRs that recognize bacterially-produced molecules
(such as LPS, peptidoglycan, flagellin, dsRNA), and
signal the immune system via cytokines (like TNFalpha)
that bacteria are present.
microbes that inhibit adherance
Streptococcus pyogenes, S. pneumoniae (by using M proteins and capsules)
microbes that kill phagocytes
Staphylococcus aureus (leukocidins)
microbes that lyse phagocytes
Listeria monocytogenes (membrane attack complex)
microbes that escape the phagosome
Shigella, Rickettsia
microbes that prevent the formation of phagosome-lysosome fusion
HIV, Mycobacterium tuberculosis
microbes that survive in the phagolysosome
Coxiella burnettii
What is the purpose of inflammation in the second line of defense? What are some signs/ symptoms?
Purpose: to destroy and remove the injurious agent limit the agent’s effects by walling it off to repair the damage Signs and symptoms: Redness Swelling (edema) Pain Heat (Loss of function)
describe the process of inflammation
cells damaged by infection release histamine,
prostoglandins, and other signaling molecules
blood clot and abscess form
vasodilation, increased vessel permeability
phagocytes (monocytes, neutrophils) migrate
margination
diapedesis
phagocytosis
tissue repair, epidermis and dermis regenerate
what is margination?
phagocytes stick to endothelium, the blood vessel cells
what is diapedesis?
phagocytes squeeze between endothelial cells
What are the four types of signaling molecules released due to cell damage?
- histamine
- kinins
- prostaglandins
- leukotrienes
Vasodilation triggered by signaling molecules
results in the _______ and _____ we association with
inflammation
redness and heat
The increased permeability of blood vessels results
in _______ or ________.
edema or swelling
acute inflammation vs. chronic inflammation
Acute inflammation, lasts relatively short time
Chronic inflammation, lasts years due to the accumulation of activated macrophages induces
fibroblasts, which synthesize collagen fibers,
resulting in fibrosis or scarring. Chronic inflammation is also a contributing factor in some cancers
what body temperature does the hypothalamus regulate the body at?
37 degrees
How is fever a second line of defense?
intensifies the effects of IFNs, inhibits growth of some microbes, and speeds up body reactions that aid repair
Describe the process of fever formation at the cellular level
Gram-negative endotoxin cause phagocytes to
release interleukin–1 (IL–1)
Hypothalamus releases prostaglandins that reset
the hypothalamus to a high temperature
Body increases rate of metabolism and shivering
which raise temperature
Vasodilation and sweating: Body temperature falls
(crisis)
What are some advantages and disadvantages to having a fever?
Advantages - Increases transferrins - Increases IL–1 activity - Produces Interferon Disadvantages - Rapid heart beat (tachycardia) - Acidosis (low blood pH) - Dehydration 44–46°C (111°F) is fatal!
What are the antimicrobial substances that are part of the second line of defense?
- complement system
- IFNs
- Iron-binding proteins
- antimicrobial peptides
What is the complement system? Is it part of the innate or adaptive immune systems?
The complement system is an enzyme
cascade that damages bacterial plasma
membranes, increases the ability of antibodies and
phagocytic cells to clear microbes and debris, and
promotes inflammation.
It is part of the innate immune system, but works
with the adaptive immune system (that which
involves antibodies and T cells).
Describe the Classical Pathway of Complement
Activation
C1 is activated by microbe-antibody complexes
C1 causes C2 to split into C2a + C2b
C1 causes C4 to split into C4a + C4b
C2a* combines with C4b, and together they split
C3
C3a and C3b initiate the complement cascade
Once the complement pathway has been activated, what happens during the complement cascade?
C3b
binds to microbe and enhances phagocytosis, a
process called opsonization (enhances
phagocytosis)
splits C5
C5b, C6, C7, C8 and multiple C9 fragments form a
membrane attack complex, which punches a hole
in the microbe, causing lysis
C3a and C5a bind to mast cells which release
histamine and other signaling molecules
C5a is a chemotactic factor, which attracts
phagocytes to the infection site
What are the key effects of the complement pathway?
Opsonization or immune adherence, which
enhances phagocytosis
Formation of membrane attack complex which leads
to cytolysis (cell lysis)
Attraction of phagocytes to the infected area
inflammation stimulated by complement
causes opsonization (complement)
C3b
cause cell lysis (complement)
C5b + C6 + C7 + C8 + C9
cause inflammation (complement)
C3a + C5a
Describe the Alternative Pathway of Complement
Activation
- C3 combines with factors B, D, and P (which are host proteins attracted to the bacterial cell surface) on the surface of the microbe
- This causes C3 to split into C3a and C3b
Describe the Lectin Pathway of Complement
Activation
- Lectin binds to an invading cell
- Bound lectin splits C2 and C4
- C2a and C4b combine to activate splitting of C3
What are some of the methods by which bacteria can evade complement?
- Capsules prevent complement activation
- Some surface lipid-carbohydrates prevent
membrane attack complex (MAC) formation - Some bacterial enzymes digest C5a
(C5a peptidase), which inhibits the infiltration of
neutrophils and macrophages to the infection site
What is the role of iron in innate immunity?
- bacteria need lots of iron
- iron is hard to get in the environment
- siderophores are secreted bacterial proteins that
sequester iron from their environment and allow the
microbes to more easily take it up - animal hosts have iron binding proteins, such as
transferrins, that transport and store iron
What are some characteristics of antimicrobial peptides?
- extremely small proteins: 12-15 amino acids long
- very diverse; more than 600 known
- broad spectrum
- not specific
- lyse bacterial cells
- inhibit cell wall synthesis
- destroy RNA and DNA
What are interferons?
Interferons are cytokines, signaling molecules
between cells during an immune response
interferons that cause cells to produce
antiviral proteins that inhibit viral replication
IFN-alpha and IFN-beta
interferons that causes neutrophils and macrophages
to phagocytize bacteria
IFN-gamma
What is the mechanism by which interferons work?
Production of interferons occurs mainly in response to microbes, such as viruses and bacteria, and their products. Binding of molecules uniquely found in microbes by pattern recognition receptors, such as membrane bound Toll like receptors, can trigger release of IFNs.
IFNs released by the virus-infected host cell bind to plasma membrane or nuclear membrane receptors on uninfected neighboring host cells, inducing them to synthesize antiviral proteins (AVPs).
AVPs degrade viral mRNA and inhibit protein synthesis and thus interfere with viral replication
