Chapter 16 Micro Flashcards
What is susceptibility?
Able to be productively infected
What is resistance?
Unable to allow a productive infection
What is immunity?
An active process that prevents establishment or progression of infection
What are direct types of immunity?
Innate, adaptive and 3rd line of defense
What is innate immunity?
Defenses against any pathogen, present at birth
What are examples of the first line of defense?
physical factors
chemical factors
normal microbiota
What is the second line of defense?
non-specific physiologic processes
What is adaptive immunity?
Specific resistance to a specific pathogen, develops over time
What is the 3rd line of defense?
Specialized lymphocytes T cells and B cells
Antibodies
What are physical factors for first line of defense?
skin, mucus, ciliary escalator, epiglottis, saliva, urine, vaginal secretions
What does skin do?
forms physical barrier to entrance of microbes
What is the epidermis?
consists of tightly packed cells with a thick layer of keratin-containing dead cells
dryness inhibits microbes
water-tightness blocks microbes
shedding removes microbe
What is the dermis?
inner layer, connective tissue
What is the mucus membrane?
are an epithelial layer lining the respiratory, gastrointestinal, urogenital, visual, and auditory systems. They inhibits the entry of many microbes, but not as effective as intact skin
What is mucus?
traps microbes in respiratory and GI tracts. It is secreted by, covers, and protects cells of the mucus membrane
What is the ciliary escalator?
Cilia is the surface projection on cells of the respiratory tract that move mucus and trapped microbes
What is the lacrimal apparatus?
Tears flow from lacrimal glands under eyelid to lacrimal canal
washing and dilution by tears keeps microbes from settling on eye surface
What is sebum?
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
What does a pH of 6 or lower inhibit?
Bacteria and fungi! Gastric juice ph: 1.2-3.0 Vaginal secretions ph: 3-5 Skin pH: 3-5 Saliva and urine contain urea which is bacteriostatic
What is a lysozyme?
Lysozyme is a small enzyme that attacks the peptidoglycan chains in the cell walls of bacteria, causing the cells to burst
*Flemming discovered lysozyme as antibiotic
What microorganism is responsible for peptic ulcers?
H.pylori
What does the second line of defense consist of?
hematopoietic cells, particularly phagocytic cells
inflammation
fever
more antimicrobial substances
What are hematopoietic cells and what is their role in the body?
- RBC carry O2 and Co2
- WBC function in immunity and injury
- Travel by circulation
- Move in and out of intestinal space
- Develop from stem cell
Increase in white cell count leads to what?
Leukocytosis
Decrease in white cell count is what?
Leukopenia
What is the circulation of the lymphatic system?
blood plasma —> interstitial fluid —> lymph —> blood plasma
Lymph ultimately flows where?
Toward the heart
What are the components of the lymph system?
Lymphoid tissues, nodes and organs
What are neutrophils?
live only a short time
predominate early in infections
What are macrophages?
last up to several months
predominate later in infections
What is phagocytosis?
Ingestion of microbes
or particles by a cell, performed by phagocytes
What are the 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
What are 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 TNF-alpha) that bacteria are present
How do some microbes evade phagocytosis?
-Inhibit adherence, m proteins and capsules Example: S. pyognes -Kills phagocytes, leukocidins Ex: S. aureus -Lyse phagocytes, membrane attack complex Ex: L. monocytogens -Escape phagosome Ex: Shigella -Prevent phagosome lysosome fusion Ex: HIV -Survive in pahgolysosome EX: Coxiella burnetti
What is the purpose of inflammation?
to destroy and remove the injurious agent
limit the agent’s effects by walling it off
to repair the damage
What is inflammation?
confines and destroys microbes and initiates tissue repair
Signs and symptoms of inflammation include:
Redness Swelling (edema) Pain Heat (Loss of function)
What is 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: phagocytes stick to endothelium, the blood vessel cells
- diapedesis: phagocytes squeeze between endothelial cells
- phagocytosis
- tissue repair, epidermis and dermis regenerate
What signaling molecules are released by cell damage?
-Histamine, kinins, prostaglandins, leukotrienes
Vasodilation…
triggered by signaling molecules results in the redness and heat we association with inflammation.
What is acute inflammation?
lasts relatively short time
What is chronic inflammation?
lasts years
accumulation of activated macrophages induces fibroblasts, which synthesize collagen fibers, resulting in fibrosis or scarring
What is the function of fever?
Intensifies he effects of interferons, inhibits growth of some microbes and speeds up some body reactions that aid in repair
What is fever and its mechanism of action?
Abnormally high body temperature
Hypothalamus normally set at 37°C
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 the advantages of fever?
- Increases transferrins
- Increases IL–1 activity
- Produces Interferon
What are some disadvantages of fever?
Rapid heart beat (tachycardia)
Acidosis (low blood pH)
Dehydration
44–46°C (111°F) is fatal!
What are some antimicrobial substances?
Complement system, interferons, iron binding proteins, AMPS
What is the complement system?
- increases 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
- *part of innate immune system but works w adaptive
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
Describe 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 effects of complement activation?
- 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
What is the alternative pathway of complement activation?
- C3 combines with B,D and P factors on microbe surface
- Causes C3 to split into fragments C3a and C3b
What is the lectin pathway of complement activation?
- lectin binds to invading cell
- bound lectin splits c2 and c4
- c2a and c4b combine and activate c3
What are capsules?
prevent complement activation
What do some surface lipid carbs do?
prevent membrane attack complex (MAC) formation
What do 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?
- 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 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
IFN-alpha and IFN-beta: Cause cells to produce antiviral proteins that inhibit viral replication
IFN-gamma: Causes neutrophils and macrophages
to phagocytize bacteria
