Changes

==Introduction==

==Introduction==

[[Image:ELISA.jpg|thumb|right|150px|Double Antibody Sandwich ELISA]]

[[Image:ELISA.jpg|thumb|right|150px|Double Antibody Sandwich ELISA]]

The Enzyme Linked Immunosorbent Assay (ELISA) is an immunoassay commonly used to detect the presence of an antigen or antibody in a sample. It is a powerful tool in clinical immunology and can be used to determine whether an individual has been exposed to a specified pathogen. Utilizing the principle of antigen-antibody interaction, the test allows easy visualisation of results and, since its introduction in 1971, has quickly replaced radioimmunoassays for diagnostic purposes.

The Enzyme Linked Immunosorbent Assay (ELISA) is an immunoassay commonly used to detect the presence of an antigen or antibody in a sample. It is a powerful tool in clinical immunology and can be used to determine whether an individual has been exposed to a specified pathogen. Utilising the principle of antigen-antibody interaction, the test allows easy visualisation of results and, since its introduction in 1971, has quickly replaced radioimmunoassays for diagnostic purposes.

*There are two basic types of ELISA:

*There are two basic types of ELISA:

*Detection and identification of disease agents, e.g. type and subtype

*Detection and identification of disease agents, e.g. type and subtype

*Identification of specific antibodies, e.g. used in serodiagnosis for epidemiological studies

*Identification of specific antibodies, e.g. used in serodiagnosis for epidemiological studies

*Quantification of specific antibody isotypes, e.g. IgM/IgG ratio

*Quantification of specific antibody isotypes, e.g. [[IgM]]/[[IgG]] ratio

==Techniques==

==Techniques==

----

----

===Non-competitive ELISA===[[Image:Sandwich elisa.png|thumb|right|100px|The sandwich ELISA - Copyright J M Vincour]]

===Non-competitive ELISA===

[[Image:Sandwich elisa.png|thumb|right|100px|The sandwich ELISA - Copyright J M Vincour]]

'''Double Antibody Sandwich''' (for antigen detection)

'''Double Antibody Sandwich''' (for antigen detection)

# Antibody is adsorbed onto solid phase

# Antibody is adsorbed onto solid phase

# Sample serum is added- class-specific antibody in the serum binds to antiglobulin

# Sample serum is added- class-specific antibody in the serum binds to antiglobulin

# Wash

# Wash

# Antigen is added- attaches to specific antibody  

# Antigen is added - attaches to specific antibody  

# Wash

# Wash

# Enzyme-labeled antibody is added

# Enzyme-labeled antibody is added

# Enzyme substrate is added

# Enzyme substrate is added

''visualised product = amount of enzyme-labelled antigen''

''visualised product = amount of enzyme-labelled antigen''