ELISA and the Immune Response

A complete set of 100 vocabulary flashcards covering the ELISA protocol, immune system functions, diagnostic applications, and laboratory materials described in the lecture notes.

ELISA

Enzyme-linked immunosorbent assay, a test that detects antibodies in blood to determine exposure to a disease.

Antigens

Molecules that cause the body to mount an immune response, including components of bacteria, viruses, and fungi.

Antibodies

Proteins that recognize a specific antigen and bind tightly to it, flagging invaders for destruction.

Immunology

The study of the immune system.

Primary antibodies

Antibodies used in an immunoassay to recognize specific antigens, conferring specificity to the assay.

Secondary antibodies

Antibodies that recognize and bind to primary antibodies, prepared by injecting antibodies from one species into another.

Conjugated antibody

An antibody that is physically attached to an enzyme.

Acquired/Adapted/Specific Immune system

The portion of the immune system that has a memory component and produces antibodies.

Negative ELISA result color

Clear or colorless.

Positive ELISA result color

Clear to blue.

Direct ELISA

An ELISA where the primary antibody is also the conjugated antibody.

Indirect ELISA

An ELISA that amplifies a positive signal through specific interactions and multiple keys for a lock.

Sandwich ELISA

One of the four main types of ELISA mentioned in the protocol.

Competitive ELISA

A specific type of ELISA assay mentioned alongside direct, indirect, and sandwich methods.

HRP

Horseradish peroxidase, an enzyme conjugated to secondary antibodies that produces a blue color in the presence of substrate.

TMB

The substrate used in this experiment that turns blue when reacted with HRP.

Seroconversion

The appearance of antibodies in the blood, typically used in the context of HIV infection timing.

$10^6$ to $10^{11}$

The estimated number of different antibodies circulating in the blood.

$$15\%$$

The percentage of total blood serum protein made up by antibodies.

IgG

An immunoglobulin whose levels begin to rise approximately 3 weeks after IgM levels drop.

IgM

The first type of antibody produced within a week of disease exposure.

p24

The HIV capsid protein bound to IgG in referenced X-ray crystallography structures.

1IGY

A Protein Data Bank (PDB) identification code for antibody structures.

1AFV

A PDB identification code used to manipulate structures in software like Rasmol.

Rasmol

A free online software used to manipulate protein structures.

Protein Explorer

A software tool mentioned for visualizing structures from the Protein Data Bank.

Hydrophobic interaction

The interaction that allows purified disease antigens to bind to the plastic wells of a microplate strip.

Adsorb

The process where proteins bind to the plastic wells in an immunosorbent assay.

Western blot

A second type of assay used to confirm positive HIV ELISA results.

hCG

Human chorionic gonadotropin, a hormone appearing in blood and urine within days of fertilization.

Anti-hCG antibody

An antibody labeled with a pink compound used on the wick area of a pregnancy dipstick.

Capillary action

The process by which the pink hCG-antibody complex migrates up the dipstick strip.

Test zone

An area on a dipstick containing fixed, unlabeled anti-hCG antibody that forms a pink stripe if hCG is present.

Control zone

A built-in area on dipsticks containing unlabeled secondary antibody to ensure the test is valid.

False negative

When a positive sample gives a negative result, potentially due to immunosuppression or testing too early.

False positive

When a negative sample gives a positive result, potentially due to contamination or recent vaccinations.

Primary response

The initial, slower immune response following first exposure to a disease.

Secondary response

A stronger and faster immune response occurring the second time the body is exposed to a disease.

Vaccination

The principle of exposing the body to a harmless disease agent to cause a primary immune response.

Booster shots

Injections designed to cause a secondary immune response.

SARS

Severe acute respiratory syndrome, a disease for which the CDC and WHO prioritized ELISA development.

CDC

The US Centers for Disease Control.

WHO

The World Health Organization.

Microplate strip

A 12-well plastic tool used to perform the ELISA protocol.

Green tube (AG)

The tube containing $1.5\,ml$ of purified antigen.

Violet tube (+)

The tube containing the positive control for the laboratory procedure.

Blue tube (-)

The tube containing the negative control for the laboratory procedure.

Orange tube (SA)

The tube containing $1.5\,ml$ of the secondary antibody.

Brown tube (SUB)

The tube containing the enzyme substrate.

Yellow tubes

Tubes containing the student serum samples to be tested.

Wash buffer

Phosphate buffered saline with $0.05\%$ Tween 20 used to remove unbound reagents.

$$50\,\mu l$$

The fixed volume transferred for antigen, controls, serum samples, and reagents.

Incubate for 5 minutes

The time allowed for proteins to bind to the plastic wells or for antibodies to bind to targets.

Triplicate

The practice of assaying each sample in three wells to ensure accuracy and check for errors.

Harris et al. 1998

One of the studies referenced for the structure of IgG bound to HIV p24.

Momany et al. 1996

A source cited for X-ray crystallography data of antibody-antigen structures.

Disulfide bonds

Structural components of an antibody connecting heavy and light chains.

Heavy chain

One of the two types of protein chains that make up the structure of an antibody.

Light chain

The smaller of the protein chains in the Y-shaped structure of an antibody.

Fetal protein

A protein produced by a fetus that can be detected in a mother's urine during pregnancy.

Immunosuppression

A condition, sometimes caused by drugs after transplants, that can lead to false negative ELISA results.

Inactivated influenza virus

An example of a disease agent used in vaccines that cannot harm the patient.

Pink compound

The substance used to label anti-hCG antibodies in over-the-counter pregnancy kits.

Microplate strip

The 12-well component where the immunosorbent assay is performed.

Binding

The action of the antigen adhering to the plastic wells or antibodies attaching to antigens.

Key-to-a-lock

The analogy used to describe the very specific interaction between an antibody and an antigen.

Magic bullets

A metaphor for antibodies seeking out and attaching to target antigens.

Foreign entities

The description biologists used 100 years ago for antigens invading an animal.

Serum

The portion of blood containing many different antibodies used for samples in ELISA.

12-well microplate strips

The specific hardware item used where one strip serves four students.

Phosphate buffered saline

The base liquid for the wash buffer used in the protocol.

Tween 20

A reagent present at $0.05\%$ in the phosphate buffered saline wash buffer.

Disposable plastic transfer pipet

The tool used to fill wells with wash buffer during the washing steps.

Paper towels

Used to blot and tap out samples and wash buffer during the assay.

Black marking pen

Used to label the outside walls of each well in the 12-well strip.

Yellow tips

Pipette tips used with the fixed-volume or adjustable micropipet.

$$0.25\,ml$$

The volume of student samples provided in the yellow tubes.

$$1.5\,ml$$

The volume of purified antigen, secondary antibody, and substrate provided in their respective tubes.

$$0.5\,ml$$

The volume of positive and negative controls provided in the violet and blue tubes.

Step 5

The specific washing procedure involves tipping the strip, tapping on paper towels, and filling with wash buffer.

Step 1 of Pregnancy Test

Coating the wick area of the dipstick with anti-hCG antibody labeled with a pink compound.

Step 4 of Pregnancy Test

The control zone captures unbound pink complex to show a pink stripe in both positive and negative results.

Double pink stripes

The visual result indicating a positive pregnancy test.

One pink stripe

The visual result indicating a negative pregnancy test.

Primary Antibody interact with Antigen

The first interaction in an indirect ELISA before the secondary antibody is added.

Secondary Antibody interact with Primary Antibody

The specific interaction that occurs in an indirect ELISA to provide amplification.

HIV

Human Immunodeficiency Virus, the virus that causes AIDS and is often tested for using ELISA.

AIDS

Acquired Immunodeficiency Syndrome.

Influenza virus

A pathogen used as an example for how vaccination ensures a rapid immune response.

Bacteria

A type of infectious agent that can act as an antigen; the text notes they also have 'memory' components.

Fungi

One of the three types of infectious agents listed as possible antigens.

Human cells

Listed as a potential type of antigen alongside viruses and fungi.

Animal cells

Listed as a physical entity that can act as an antigen.

Colorless solution

The initial state of the enzyme substrate before it is chemically changed.

Blue solution

The final state of the substrate after being chemically changed by the enzyme HRP.

Experimental errors

Potential issues in results that are guarded against by using controls.

Protein Data Bank (PDB)

A bioinformatics database where structures 1IGY and 1AFV can be downloaded.

Unbound pink complex

The substance that binds to the control zone of a pregnancy dipstick to confirm the test is valid.

Antigen binding time

5 minutes, the time proteins take to bind to the plastic well via adsorption.

Protein-protein interactions

The specific biochemical interactions that are key to the functionality of an ELISA.