Micro - ch.17 - Applications of Immune Responses

herd immunity

indirect protection from infection disease that occurs when sufficient proportion of as population becomes immune through vaccination or prior exposure

• reduces likelihood of disease transmission

What is attenuated vaccine?

live vaccine from weakened (attenuated) form of actual pathogen

• causes immune response but doesn’t cause healthy individuals disease

What are the pros and cons of attenuated vaccines?

pros: lifetime protection

cons: can mutate back to potent form

List some approaches to making a vaccine

• using whole virus/bacterium

• parts that trigger immune system

• just the genetic material

Whole agent

entire pathogens

• stimulates immune response to build

• weakened or inactive

toxoids

inactivated bacterial toxins

• made to be harmless but stimulate immune system

What is an example of a toxoid?

tetanus shot makes the body antibodies

subunit vaccines

only fragments of virus/bacterium

proteins or sugars

• not live and can not cause disease 

adjuvant

vaccine that includes an added substance “adjuvant”

• enhance bodies immune response to antibodies

• especially if antigen alone is not strong enough to provoke immunity

aluminum salts

an adjuvant

keeps antigen concentrated at injection site - “depot” method - prolong stimulation

mRNA vaccines

modern vaccine → synthetic mRNA that contains instructions to code for a protein → usually one on surface of virus → foreign →stimulates immune system

viral vector vaccine

genetically engineered virus to carry DNA encoded antigen - usually protein from a pathogen - into the body

• host cell uses DNA to produce antigen internally which immune system recognizes and responds to

• only antigens multiply

serum

blood allowed to clot and without anticoagulant which samples are centrifuged and liquid serum supernatant 

→ antibodies, electrolytes, hormones 

What is serum made of?

plasma and clotting factors like antibodies, electrolytes, hormones

What are some uses for serum?

• detects antibodies/antigens

• measure hormone levels/biomarkers

• oncology and allergy testing 

titer

way to measure how much antibodies/antigens are present in sample

how does a titer work?

looks for dilution at which a small amount of detectable antibody or antigen exists

1. dilute sample step by step (less concentration)

2. test each dilution for reaction (binding or agglutination) 

3. titer is highest dilution (lowest concentration) at which reaction is still visible 

seroconversion

process during which persons blood changes from being negative for specific antibodies to positive after infection/vaccination 

Immunological tests

**tests for serum

• direct and indirect fluorescent antibody tests

Direct fluorescent antibody tests

lab technique used to detect specific antigen by using antibody labeled with fluorescent dye

Indirect fluorescent antibody test

lab technique used to detect specific antigen by using 2 antibodies labeled with fluorescent dye

How do immunological tests work?

1. known antigen is fixed on slide

2. ask patients serum (antibodies should be present and bind)

3. add fluorescent labeled secondary antibody that specifically binds to patients antibodies

4. wash of excess antibodies and exam

ELISA

lab test used to detect and measure antibodies and antigens in blood

First step of ELISA test

known antigen or antibody is attached to plate

In the second step of ELISA, what is added?

the patients sample is added which contain antibodies to binds = coats antibody

What is added after the patients sample in ELISA test?

secondary antibody linked to an enzyme is added and binds to target (step 4)

What is the purpose of adding color changing substrate?

causes substrate to react to enzyme and change colors and indicate its presence (step 5)

What is the last step of ELISA test?

color intensity is measured by a “spectrophotometer” to determine how much target is in sample 

Western Blot

proteins separated by gel electropheresis transferred into membrane

• uses labeled antibodies to bind specific proteins

• identifies presence, size, abundance of target proteins

• used for protein expression analysis, disease diagnostics and more 

detects antibodies

complement fixation

detect presence of specific antibodies in patient blood by seeing if complement system is activated

how does complement fixation work?

1. mix blood sample with known antigen

2. add complement proteins

3. if patients find and stick to antigen, the complement is used (gets fixed)

positive result of complement fixation

antibodies (check) binds to added antigen and fix complement 

sheep RBC are added and would remain intact and settle at bottom 

negative result of complement fixation

antibodies (none) means complement is free to attach added sheep RBS and breaking the cell turning it pale pink

Neutralization test

checks whether antibody in sample can block (neutralize) the harmful substance of. a toxin, virus, or microbe

(microbe/toxin + patient serum)

(+): cells survive and patient has antibodies

(-): cells die