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135 Cards in this Set
- Front
- Back
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Normal flora are
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"commensal mutualistic orgnaisms"
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Microbe populations vary with:
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-tissue conditions
-ph, moisture, other microbes present -intestinal flora varies with food eaten |
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normal flora can cause disease if reach __________ __________
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abnormal location
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Sites where bacteria are normally found:
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-skin
-oral cavity -gastrointestinal tract -urogenital tract |
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skin is difficult to colonize because:
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-dry, acidic, salty, and contains protective oils
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Microbes grow mostly in:
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moist areas: underarms, genitals, etc.
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Microbes are associated with:
pH 4-6 |
sebaceous (oil) glands & apocrine sweat glands
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Factors that affect normal flora:
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weather, age, personal hygiene
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Bacteria that are associated with the skin are mostly:
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Gram Positive
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Staphyloccocus
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-gram +, aerobic cocci
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Propionibacterium
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Gram +, anaerobic rods
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Propionibacterium acnes:
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can cause acne
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Acinetobacter
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gram -, rods
one of the few gram - bacteria found on skin |
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Bacteria in the mouth prior to tooth formation are mainly:
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aerotolerant anaerobes such as streptococcus and lactobacillus
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Acidic glycoproteins in saliva form a layer on teeth providing a firm:
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attachment site for microbes, usually a streptococcus species.
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Extensive growth for microbes on teeth results in:
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thick bacterial layers called dental plaque.
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Microflora of dental plaques make:
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acids that decalcify tooth enamel; results in dental caries (tooth decay,cavities).
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Tooth surfaces in and near the ___________are common sites of tooth decay floss!!!
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gingival crevice where food particles remain
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Diets high in ________ are cariogenic (cavity causing)!
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sucrose
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Lactic acid bacteria:
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ferment sucrose to lactic acid.
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Diets containing ______ during formation of tooth enamel make teeth more resistant to tooth decay.
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fluoride
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Incorporation of fluoride into the calcium phosphate crystal matrix increase resistance to ______.
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decalcification
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Stomach pH ~ 2, only acid-tolerant bacteria can colonize ____________________.
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stomach wall
ex: Helicobacter pylori (peptic ulcers in stomach lining) |
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# of bacteria increases down through small intestine due to:
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rising pH
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Duodenum:
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few bacteria due to stomach acids, mainly gram + cocci and bacilli.
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Jejunum:
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-Enterococcus and Lactobacillus
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Ileum:
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-microbiota reflects that of large intestine (large # of bacteroides and facultative aerobes like E. coli)
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Large Intestine is a fermentation vessel:
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many bacteria(> 300 species), mostly anaerobes
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Commonly _______ of intestinal contents
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10" of bacterial cells/gram
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Small number of _________ consume oxygen which allows obligate aerobes ot grow
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facultative aerobes (E. coli)
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Bacteria in large intestine:
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-ferment ingested food
-provide nutrients -inhibit pathogens |
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Diet affects intestinal flora: example:
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more meat = more bacteroides
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Vitamins produced by intestinal flora:
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-Vitamin B12, K, riboflavin, thiamine
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Antibiotics- can reduce # of normal intestinal flora, can lead to ___________.
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digestive problems
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Probiotics supply ________ and _________
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Lactobacillus and Bifidobacterium
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Common anaerobic intestinal flora are:
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-Bacteroides
-Clostridium -Enterococcus |
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Many adults have methanogens which:
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-convert hydrogen and carbon dioxide into methane gas.
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Bacteria in the intestinal tract are:
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commonly being displaced by downward by the flow of material and replaced by new microbes.
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The growth rate of bacteria in large intestine is:
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1-2 doublings per day
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Upper respiratory tract:
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nasopharynx, oral cavity, throat
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Most bacteria breathed in:
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-trapped in mucus
-many opportunistic pathogens in nasopharynx |
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Staphylococcus aureus
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-causes sinus and ear infections
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Streptococcus pneumonia
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-causes sinus infections and bronchitis
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Steptococcus pyogenes
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-causes sinus infections and strep throat
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Corynebacterium diphtheriae
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-causes diphtheria
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Bacteria are not normally found in Lower respiratory tract. It is:
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lined with cilia (push bacteria and dust particles up where they are caught in mucus and saliva)
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Kidney and Bladder:
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are sterile
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Several types of facultative anaerobes are associated with urethra: (mostly gram- rods)
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-Escherichia
-Klebsiella -Proteus -Neisseria (gram - cocci) |
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Lactobacillus acidophilus:
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often found in vagina due to acidic pH
-acidic secretions prevent pathogens |
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Commensal flora benefits human host:
It ------ |
- makes vitamins
-digests food -prevents colonization by pathogens |
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Opportunistic pathogens:
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-surface breach allows entry
-immunocompromised host (Clostridium difficile) |
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Innate immunity:
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-barriers to infection
-nonspecific reaction to destroy invading cells |
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Adaptive immunity:
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-reaction to specific antigen
-(parts of foreign proteins, sugars, chemicals -body reacts to antigen when exposed (retais memory of these antigens, faster response if exposed a second time) |
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White blood cells:
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neutrophils and monocytes
engulf and destroy microbes (monocytes: macrophages and dendritic cells) basophils and eosinophils (release toxins to poison microbes) |
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Lymphocytes:
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-T cells regulate specific immune response
-B cells produce antibodies to bind to antigens |
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The host's ability to resist infection depends on:
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-Age (yound and old more susceptible
-Stress (high stress increasses susceptibility) -diet low in protein and calories -general health and lifestyle (smoking, excess alcohol, drugs, and lack of sleep) -prior or concurrent disease (hospital patients require nosocomial infections) -generic conditions (esp. if infecting the immune system) |
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Immunity:
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the ability of an organism to resist infection
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All cells involved in immunity originate from common stem cells _________.
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in bone marrow
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Immune system:
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protects against foreign cells and macromolecules.
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Antigen/Immunogen:
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foreign cells and macromolecules than induce immume system.
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2 types of immunity:
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-Naturally aquired immunity
-Artificially aquired immunity |
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Naturally aquired immunity:
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can be classified as active or passive
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Naturally aquired active immunity:
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host produces antibodies & t-cells in response to an infection.
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Active immunity:
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can last for years or a lifetime
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Naturally acquired passive immunity:
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Occurs when antibodies are passed from one host to another. Ex: placenta from mother to fetus
-circulate for months after birth in infants system -last few weeks to months |
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Artificially acquired immunity:
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-can (also) be classified as active or passive
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Artificially acquired active immunity:
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result of vaccination
host makes antibodies that can last for years |
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Vaccinations/Immunizations:
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-to reduce risk vaccines contain inactivated pathogens or their products.
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Toxoid
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-chemically modified exotoxin retains antigenicity but loses toxicity
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Killed bacterial cell
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-formaldehyde, heat, (Cholera)
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Inactivated virus
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-formaldehyde
(Salk polio vaccine, Influenza) |
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Live cells/virus-more effective:
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-attenuated: has lost it's virulence
(TB chickenpox) |
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Purified polysaccharide:
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-Meningitis
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Artificially acquired passive immunity:
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-host recieves antibodies from another host that has formed antibodies against a specific antigen
-lasts only a few weeks |
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Innate or non-specific immunity:
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-first line of defense
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Phagocytic leukocytes
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-engulf and destroy pathogens
-move by ameboid motion -contain lysosomes |
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Lysosomes
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-H2O2, lysozyme, proteases, phospatases, nuclease, and lipases that destroy invader
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Neutrophils are phagocytic leukocytes that:
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-accumulate in large numbers in blood or inflammation site and indicate active infection
-PMNs (polymorphonuclear leukocytes) |
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Phagocytic leukocytes are called monocytes when:
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-they are circulating the bloodstream
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Phagocytic leukocytes are called macrophages when:
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-when in enters tissue
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Antigen presenting cells:
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- macrophage present peptide antigens to T cells to activate a specific immune response
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Phagocytes recongnize pathogens by coming in contact with them. Proteins on surface of phagocyte :
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-recognize specific structural component (ex. LPS on pathogen!)
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Ingestion of the pathogen activates phagocytes to produce toxic oxygen molecules:
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- to kill ingested pathogen.
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Inflammation-nonspecific reaction; occurs at infection site to:
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-localize and destroy pathogen.
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Macrophages secrete vasoactive factors that contribute to characteristics associated with inflammation:
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- increase vascular permeability
- increasing volume (swelling, edema) -reddening (erythema) -local heating (fever) |
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Septic shock:
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-a systemic inflammatory response, spreading of inflammatory cells & chemicals through blood and lymph
-life threatening due to loss of blood volume and high fever |
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Adaptive immunity: immune system:
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-reacts to specific antigens
-Parts of foreign proteins, sugars, chemicals -retains "memory of those antigens" -faster response if exposed a second time |
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Humoral immunity:
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-production of antibody proteins
-each binds a different antigen |
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Cellular immunity:
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- T cells that bind to different antigens
- Kill pathogens, control antibody production |
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Immunogeniticity
Immune system reacts to antigens: _____________ are good antigens. |
- peptides
-fixed nonrepetitive shape (unlike lipids, nucleic acids) |
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Immune reaction is specific:
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-response to one antigen usually does not protect against a different antigen.
-attack from non-host -blood types: type A attacks type B blood cell antigen -AB has both antigens, won't make antibodies |
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Adaptive or Specific immunity
Antigen presenting cell (APC)- |
-macrophage or B cell that presents a processed antigen, to a T cell
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Antibody immunoglobulin-
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: a soluble protein produced by B cell; reacts with antigens
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Following ingestion with pathogen, phagocytes, and B cell lymphocytes present antigens on their cell surface to T cell lymphocytes resulting in:
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-Cell mediated immunity (T cells)
-antibody-mediated humoral immunity (antibodies and B cells) |
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Cell mediated immunity:
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-involves T cell lymphocytes
-mainly protects against tumor cells and virus infected cells |
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Synthesis of T cells:
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-derived from bone marrow stem cells
-stem cells migrate to the thymus and differentiate into T lymphocytes |
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When phagocytes digest pathogens:
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- polypeptides from pathogen are bound to surface of phagocyte- Antigen presentin cell (APC)
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When APC binds to a T cell, it causes the:
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-T cell to differentiate
- each T cell type can recognize antigen that was presented to the original T cell |
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Helper T cells:
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- bind B cells and activated them
-activated B cells differentiate into plasma and memory cells |
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Cytotoxic T cells:
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-destroy tumor cells and infected cells by releasing cytotoxin
-also recognize grafted tissues and organs as foreign |
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T-cell receptors:
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-receptor attached to T-cell surface membrane
-binds antigen specifically |
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Structure of T-cell receptors:
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-2 peptides (d & B) each with a constant variable domain
-variable domains bind antigen |
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Major Histocompatibility Complex:
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-"self" proteins on surface of cells
-bind to antigen |
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-Antigen/MHC complex is :
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-recognized by T- cell receptor
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Class I MHC proteins on surface of cell;
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presents intracellular antigens to T-cytotoxic cells.
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Class II MHC proteins on surface of antigen presenting cells:
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:presents extracellular antigens to helper T-cells.
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T-cells become activated when:
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-antigen/MITC binds to a T-cell receptor.
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Cell-mediated immunity:
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-T-cytotoxic cells destroy th antigen presenting cell or T-helper 1 cells recruit macrophages to destroy antigen bearing-cell.
(tumor cells, transplanted organs and tissues are attacked by TH1 cell activated macrophages.) |
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Antibody-mediated immunity: also called humoral immunity
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-Antibodies bind to antigens - inactivate them.
-most active against bacteria, bacterial toxins, and viruses in bloodstream. |
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Antibodies don't recognize __________.
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entire pathogen
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Recognize regions of antigen called ________________.
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epitopes
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Binding of antibody of foreign cell:
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-does not directly kill the cell
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Antibody binding:
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-activates the complements system.
-enhances the phagocytosis-opsonization -causes agglutination -neutralizes antigens |
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Enhancing phagocytosis
Antibodies bind to both: |
- a microbe and a phagocyte
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Antibody bridge increases ability to phagocyte:
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-to ingest microbes
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Antibody Structure:
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-Y-shaped protein
-IgG consists fo 4 polypeptide chains -the 2 large/heavy chains are identical & held together by 1 disulfide bond |
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The constant region of all IgG molecules:
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is the Same!
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Variable regions:
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where antigens bind.
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Specific for the antigen that the IgG molecule was made against _______________.
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-each IgG can bind to 2 antigens.
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5 classes ofn antibodies/immunoglobulins:
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-Heavy chain constant domains define class IgG.
-most abundant - 80% of Ig in serum is IgG. Gamma heavy chains -Only antibody that can be transferred through placenta. |
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Mu heavy chains-
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-2nd most abundant Ig
-1st class of antibody made in response to infection -aggregate of 5 molecules attached by disulfide bonds & j chains -can bind up to 10 antigens. |
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Alpha heavy chains-
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-IgA predominant antibody in secretions (saliva, tears, milk, mucus, etc.)
-dimer |
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Epsilon heavy chains-
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-Low concentration, responsible for allergies
-binding of antigen to IgE causes release of histamine allergies |
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Delta heavy chains-
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-found on the surface of B cells
-Binding of antigen to these antibodies stimulates the B cells to produce antibody mostly IgG |
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Synthesis of Antibodies B cells:
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-Type of lymphocytes; makes antibodies
-B cells are made and mature in bone marrow the disprese through blood and lymph -B cells collect in lymph nodes and spleen. |
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Presentation of the antigen:
1st step in making antibodies is: |
- phagocytosis of foreign cell by B cell
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Foreign cell is digested & polypeptides from that cell are bound to ___________.
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surface of cell
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Activation of the B cell:
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-next, a TH cell binds to polypeptide on B cell
-binding of the TH cell triggers B cell to divide |
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Differentiation of the B cell:
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-B cells differentiate into plasma cells (live <1 week) or memory cells live several years
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Primary immune response:
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-After initial exposure to an antigen, it takes several days (lag time) before much antibody is produced.
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Primary immune response
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- after initial exposure to takes several days before much antibody is produced.
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During this lag time:
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- new B cells are specific to this antigen.
IgM made first, then IgG |
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When host is exposed to same antigen again,
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-lag time much shorter.
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Hypersensitivities:
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-inappropriate immune response, resulting in host damage.
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Superantigens- pathogen proteins that cause widespread;
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stimulation of immune cells, resulting in massive inflammatory, response, tissue damage.
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