Micro Chp 15-21





first line defense

1. mechanical factors2. chemical factors3. normal flora

mechanical factors

- skin- keratin- mucuous membrane- ciliary escalator- glands- hair

chemical factors

- skin secrete sebum- pH 3-5- gastric juice- pH 1-3- lysozomes and peroxidase- transfeerins in blood compete for iron binding- nitric oxide- inhibits ATP production

normal flora

relationship bewteen microbes and host


give them something to survive off of and they give us something in return


we dont benefit but bacteria isnt harmful either


one benefits at the other expense

second line defenses

1. WBC2. phagocytosis3. lymphatic system




produce histamine


toxic to parasites, allergic reactions, some phagocytosis


phagocytosis as mature macrophages

fixed macrophages

spleen, liver, lungs

wondering macrophages

roam tissues


cells recruited to infection

process of phagocytosis

1. chemotaxis2. attachment3. engulfment4. phagosome lysosome fusion5. destruction6. exocytosis

cardinal signs

heat, pain, swelling, redness

chemicals released by damaged cells

histamine, kinins, prostaglandins, leukotrienes


programmed cell death

what causes fever?



fever inducing cytokines


bacterial endotoxins

what is the complement system?

- inactive proteins- strengthens adaptive immunity- casade of enzymatic reactions

name the pathways of the complement system

1. classical 2. alternative3. lectin

classical pathway

- quickest and most efficient- activation requires antibodies- membrane attack complex

alternative pathway

- easily initated- activation by C3b to cell surface

lectin pathway

- activation requires mannon-binding lectins

alpha and beta interferons

cause cells to produce antiviral proteins that inhibit viral replication

gamma interferon

causes neutrophils and macrophages to phagocytize bacteria

2 kinds of adaptive immunity

1. cell-mediated2. humoral

primary lymphoid organs

- bone marrow- B cells maturation- thymus- T cells maturation

secondary lymphoid organs

- encounter antigens- nodes, spleen, tonsils


stimulates immune system

3 antigen characteristics

1. protein structure2. can be carbohydrates3. molecular wieght > 10 kilo Daltons

2 parts of anitbody

1. Fc region (constant)- determines class2. Fab region (variable)- binding site


- first to respond to infection- pentamer but found on B lymphocytes as a monomer- only one formed by the fetus


- dominant in circulation- monomer- can cross placenta- memory


- found in secretions, not circulating- monomer in serum but dimer in secretions


- maturation of antibody response- monomer


- barely detectable in circulation- monomer- allergic rxns

clonal selection

specific response of mature B cells to an antigens epitopes

clonal expansion

repeated cycles of cell division generates population of copied antibodies


prevents toxin from interactin with cell


coating of bacteria with antibody to enhance phagocytosis

affinity maturation

- form of natural selection- occurs among proliferating B cells

cell-mediated immunity

- T cells never prducec antibodies- antigens must be present by antigen presenting cell to T cell receptor

2 components of MHC

1. class 1- expressed on every nucleated cell - binds to CD8 cells - endogenous2. class 2- expressed only on APC like macrophages - binds to CD4 - exogenous

2 parts of helper T cells

- Th1- related to cell mediated immunity, sends out cytokines- Th2- activate B cells to produce eosinophils, IgM, IgE

what does CD8 kill the cell with?


delayed hypersensitivity T cells

allergic rxns, TB test

suppressor T cells

turns off immune system when no antigen in present to avoid autoimmune effect

what do natural killer cells lack?

antigen specidicity

how do natural killer cells recognize antigens?

the Fc portion of the IgG antibodies

natural killer cells recognize destroyed host cells with...

no MHC class 1 surface molecule- important for viral infections

interleukin 1

stimulates CD4

interleukin 2

activates CD4, B, CD8, and NK cells

interleukin 12

differentiation of CD4 cells

clonal deletion

process of destroying B and T cells that react to self antigens

B cells undergo positive or negative selection?


T cells undergo positive or negative selection?


positive selection

differentiation of T cells will only occur if the cell recognizes MHC molecule

naturally acquried active immunity

antibodies resulting from infection

naturally acquired passive immunity

Ab through placenta

artifically acquired active immunity

injection of antigens (vaccines)

artifically acquired passive immunity

injection of Ab

attenuated vaccines

live, weakened form of the pathogen

inactivated vaccines

contains killed organisms or inactivated virus

what are the advantages of attenuated vaccines?

- usually a single dose- has added potential for being spread to un-immunized individuals

what are the disadvantages of attenuated vaccines?

- could cause disease in immunocompromised individuals

what is the advantage of inactivated vaccines?

- can not cause disease- immunogenic- process of gaining immunity

what are the disadvantages of inactivated vaccines?

- magnitude of response is limited- no amplification of the dose in vivo (booster shots)

examples of whole agents that are inactivated vaccines

cholera, plague, flu, salk polio

examples of fragment agents that are inactivated vaccines

DTP and hep B

what is type 1 hypersensitivitiy called?

immediate IgE mediated

immediate IgE mediated

- inherited- charaterized by immediate reaction of the sensitized individual


occurs when antigen induces plasma cells to secrete IgE antibodies

Fc region of IgE binds to receptors on what cells?

mast and basophils

what is type 2 hypersensitivity called?


type 2 hypersensitivity involves what antibodies?

IgG or IgM or ADCC that all cause cell death

examples of type 2 hypersensitivity

tranfusion rxns and hemolytic disease of the newborn

what is type 3 called?

immune complex mediated

immune complex mediated

IgG and antigens form complexes (usually adhere to the Fc receptors are destroyed and removed)

immune complex mediated initates what?

blood clotting mechanism and inflammation

immune complex mediated complexes are deposited where?

skin, kidneys, joints

type 4 hypersensitivity is called?

delayed cell mediated

what is delayed hypersensitivites due to?

cytotoxic T cells that release cytokines that initiate inflammation that attracts marcophages (nothing to due with Ab binding to Ag)


acute life threatening illness causes by infectious agent or its products circulating in blood

what are the steps for a pathogen to take in order to establish a diesase?

1. adherence2. colonization- multiplying on a body surface3. delivery of effector molecules that induce changes in the recipient cell

communicable disease

disease transmitted from one host to another

what are the 2 things for a pathogen in a communicable disease?

- must have a suitable environment (reservoir)- must leave the reservoir to be transmitted

morbidity rate

number of cases of illness divided by population at risk

mortality rate

population that dies from disease


number of new cases per specific time period


total number of existing cases

reservoirs affect....

the extent and distribution of disease

name 3 reservoirs

humans, animals, environmental (nearly impossible to elimate)

horizontal transmission

pathogen passed to next reservoir via contact with food, water or living agent

epidemiologists investigate disease outbreak to determine...

- causative agent- reservoir- route of transmission

cross- sectional study

survey of range of people to determine prevalence of number of characteristics

retrospective study

comparing to healthy individuals that already had the disease

prospective study

looking ahead to see if risk factor from retrospective study predict tendency to develop disease

nosocomial infections are known as

hospital acquired infections

what factors determines which organisms and agents are responsible for nosocomial infections?

- length of time of exposure- manner of exposure- virulence and number of organisms- state of host defenses


antimicrobial substance is synthesized and secreted by some true microorganism


antibiotic that is chemically altered after purification to impart new characteristics


antimicrobial substance synthesized in a lab

a high therapeutic index is more or less toxic to a patient?


bacteriostatic drugs

- inhibit bacterial growth- relies on host immunity to eliminate pathogen

bacteriocidal drugs

- kills bateria- useful when host defenses can not be relied upon to control pathogen

if gram (+) then antimicrobial drugs cause...

inhibition of cell wall synthesis

antimicrobial drugs can cause inhibition to...

1. cell wall synthesis- high therapeutic index2. protein synthesis- targets ribosomes3. nucleic acid synthesis- targets enzymes necessary for DNA replication4. metabolic pathways- folic acid

this drug binds to gram (-) that alters the permeability which leads to leakage of cell components and cell death

polymyxin B

synergistic drugs

2 drugs working together