Line 1: |
Line 1: |
− | {{toplink
| |
− | |backcolour = FFE4E1
| |
− | |linkpage =Immunology - WikiBlood
| |
− | |linktext =IMMUNOLOGY
| |
− | |sublink1 =Immunological testing - WikiBlood
| |
− | |subtext1 =IMMUNOLOGICAL TESTING
| |
− | |pagetype =Blood
| |
− | }}
| |
− |
| |
| ==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: |
Line 21: |
Line 12: |
| *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== |
Line 57: |
Line 48: |
| | | |
| ===Non-competitive ELISA=== | | ===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 |
| # Wash | | # Wash |
− | # Sample is added- specific antigen binds to antibody | + | # Sample serum is added- specific antigen binds to antibody |
| # Wash | | # Wash |
| # Enzyme-labeled specific antibody is added- attaches to bound antigen | | # Enzyme-labeled specific antibody is added- attaches to bound antigen |
| # Wash | | # Wash |
− | # Enzyme substrate is added | + | # Enzyme substrate is added (with dye for visualisation) |
− | ''visualised product = amount of antigen in the sample'' | + | ''visualised product = amount of antigen in the serum'' |
| | | |
| '''Antibody Class Capture Assay''' (for antibody detection) | | '''Antibody Class Capture Assay''' (for antibody detection) |
| # Class-specific antiglobulin is adsorbed onto solid phase | | # Class-specific antiglobulin is adsorbed onto solid phase |
| # Wash | | # Wash |
− | # Sample is added- class-specific antibody in the sample 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 |
| # Wash | | # Wash |
| # Enzyme substrate is added | | # Enzyme substrate is added |
− | ''visualised product = amount of specific antibody in sample'' | + | ''visualised product = amount of specific antibody in serum'' |
| | | |
| '''Indirect Method''' (for antibody detection) | | '''Indirect Method''' (for antibody detection) |
− | # Antigen is adsorbed onto solid phase | + | # Specific antigen (i.e. not from sample) is adsorbed onto solid phase |
| # Wash | | # Wash |
− | # Sample is added- any specific antibody present in sample binds to antigen | + | # Serum is added- any specific antibody present in sample binds to antigen |
| # Wash | | # Wash |
| # Enzyme-labeled antiglobulin is added- attaches to antibody | | # Enzyme-labeled antiglobulin is added- attaches to antibody |
| # Wash | | # Wash |
| # Enzyme substrate is added | | # Enzyme substrate is added |
− | ''visualised product = amount of antibody in the sample'' | + | ''visualised product = amount of antibody in the serum'' |
| | | |
| ===Competitive ELISA=== | | ===Competitive ELISA=== |
Line 93: |
Line 85: |
| # Antigen is adsorbed onto solid phase | | # Antigen is adsorbed onto solid phase |
| # Wash | | # Wash |
− | # Enzyme-labeled antibody (pre-titrated- optimal colour development) and sample are added | + | # Enzyme-labeled antibody (pre-titrated- optimal colour development) and serum are added |
| # Wash | | # Wash |
| # Enzyme substrate is added | | # Enzyme substrate is added |
− | ''visualised product = amount of enzyme-labelled antibody'' | + | ''visualised product = amount of antigen in serum sample'' |
| | | |
| '''Direct Antigen Competition''' (for antigen detection) | | '''Direct Antigen Competition''' (for antigen detection) |
| # Antigen is adsorbed onto solid phase | | # Antigen is adsorbed onto solid phase |
| # Wash | | # Wash |
− | # Antigen in sample is incubated with enzyme-labelled antibody (again pre-titrated): this is directed against the antigen on the solid phase | + | # Antigen in serum is incubated with enzyme-labelled antibody (again pre-titrated): this is directed against the antigen on the solid phase |
| # Wash | | # Wash |
| # Enzyme substrate is added | | # Enzyme substrate is added |
| ''visualised product = amount of enzyme-labelled antigen'' | | ''visualised product = amount of enzyme-labelled antigen'' |
| + | |
| + | |
| + | {{review}} |
| + | <br><br> |
| + | {{Jim Bee 2007}} |
| + | [[Category:Immunological Testing]] |
| + | [[Category:Image Review]] |