| Antibodies and antigens | specific cell components (antigens) react with specific antibodies |
| Antibody-Antigen rxn detection methods | - fluorescent antibodies: fluorescent dye attached to antibodies
- radiolabeled antibodies: radioisotope attached to antibodies
- enzyme-linked antibodies: enzyme attached to antibodies
- precipitation tests |
| Fluorescent antibodies | - fluorescent dye attached to specific antibody
- antigen-antibody complex fluoresce
- detection with fluorescent microscope |
| Agglutination tests | - clumping observed when antibodies react with target cells
- visibility improved if antibodies are bound to large particles (ex. polystyrene beads)
- toxins can be detected |
| Radio-immuno assay (RIA) | - radioisotope (RIA): antibody or antigen label
- antigen-antibody complex must be retained on a solid surface
- detection via radioactivity measurement using liquid scintillation counter |
| Enzyme-linked Immunosorbent Assay (ELISA) | - capture Abs (antibodies) to capture the target Ag (antigens)
- enzyme labeled Abs used to detect target Ag (ex. horseradish peroxidase, alkaline phosphatase, β-galactosidase)
- highly specific and sensitive immunological tool
- colored product made when substrate is added
- amt of product is proportional to the amount of antigen present |
| ELISA sandwich method | - microtiter well coated with Abs specific for target Ag
- food sample added to well
- mixture incubated then gently washed
- bound Ag treated with excess enzyme-labeled Ab
- mixture incubated then gently washed
- substrate for enzyme added
- enzyme action results in colored product
- amount of product is proportional to amount of Ag present |
