Post on 22-Dec-2015
Antigens & Antibodies: reactions, detection, and applications
Introduction
Adaptive immune responses are not directed against whole bacteria, protozoa, or viruses, but instead against portions of cells, viruses, and even parts of single molecules that the body recognizes as foreign and worthy of attack.
These biochemical shapes are called antigens
Adaptive Immunity Crash Course
Antigens & Antibodies
antigens stimulate the production of one or more antibodies by white blood cells. The term originally came from antibody generator
Antigens are “molecules of attack”. Our bodies respond to foreign antigens associated with pathogenic bacteria/viruses/etc. rather than the pathogen itself
Antigens & Antibodies
Antibodies (Ab), or immunoglobulins (Ig), are large Y-shaped proteins produced by B-cells in response to the presence of an antigen.
Antibodies bind to antigens and aid in defense of the body by neutralizing the pathogens possessing the antigens that stimulated their production
Actions of Antibodies
Antigens & Antibodies
Each antibody binds to a specific antigen by way of an interaction similar to the fit between a lock and a key.
Antibodies bind to antigens forming immune complexes or antibody-antigen complexes.
Applications
Antigen/Antibody Applications
Antigens and Antibodies have many uses in Biotech applications Medical Diagnostics
Vaccine Production
Locating Cellular Proteins
Immunoprecipitation
ELISA
Medical Diagnostics
Detection of particular antibodies is a very common form of medical diagnostics
In biochemical assays for disease diagnosis, a titer of antibodies directed against Epstein-Barr virus is estimated from the blood. If those antibodies are not present, either the person is not infected, or the infection occurred a very long time ago, and the B cells generating these specific antibodies have naturally decayed.
Medical Diagnostics
Antibodies raised against human chorionic gonadotropin (HCG) are used in over the counter pregnancy tests
These tests often work by using immunochromatography to detect the presence of HCG.
Immunochromotography
Test strips use antibodies to capture a molecule of interest (i.e. HCG). Accumulation of the molecule of interest causes a color change on the test strip, indicating a positive result.
Vaccine Production
A vaccine is a biological preparation that improves immunity to a particular disease.
Vaccines typically contain an agent that resembles a disease-causing microorganism
We can isolate antigenic surface proteins of pathogens and use them to produce vaccines and generate immunity.
Locating Proteins
Antibodies linked to fluorescent molecules can be used to locate proteins within cells and can be used to differentiate between cell types based on what proteins the cells are expressing.
Immunofluorescence image of the eukaryotic cytoskeleton. Actin filaments are
shown in red, microtubules in green, and the nuclei in blue.
Immunoprecipitation
Is the technique of precipitating a protein antigen out of solution using an antibody that specifically binds to that particular protein.
This is often used to isolate and concentrate a particular protein from a sample containing many different proteins.
Immunoprecipitation
ELISA
Enzyme-linked immunosorbent assay (ELISA) is a test that uses antibodies and color change to identify a substance.
ELISA
Antigens from a sample are attached to a surface (usually they are immobilized by binding to embedded antibodies).
A further specific antibody is applied over the surface so it can bind to the antigen. This antibody is linked to an enzyme
ELISA
In the final step, a substance containing the enzyme's substrate is added. The enzymes reaction with its substrate produces a detectable signal, most commonly a color change in the substrate
ELISA
ELISA
The ELISA can been useful as a diagnostic tool in medicine to check for the presence of certain antigens
ELISA is also often used for quality-control in various industries (i.e. ELISA can be used to check for the presence of allergens in food).