Introduction:
- ELISA (enzyme-linked immunosorbent assay) is a plate-based assay technique designed for detecting and quantifying substances such as peptides, proteins, antibodies and hormones
- Most common substrate used: TMB (Tetramethylbenzidine)
- Most common enzyme used: HRP (Horseradish peroxidase).
Types & Principles:
- Direct ELISA:
- Detect Ag using specific Ab
- Specificity is high.
- Indirect ELISA:
- Detect Ab using conjugates
- Conjugate = Anti-human immunoglobulin labelled with enzyme
- Sensitivity is high.
- Competitive ELISA:
- Detects Ab using specific Ab labelled with enzyme
- There is a competiton between patient’s Ab & specific Ab with enzyme, hence the name ‘Competitive ELISA’.
- Capture ELISA:
- Detect specific isotype of Ab in patient’s serum (IgM/ IgG) using specific monoclonal Ab (also known as ‘capture Ab‘)
- Dye used: FITC (Fluorescein Isothiocyanate).
