ELISA

Options

A. Uses complement mediated cell lysis
B. Uses rediolabelled second antibody
C. Involves addition of substrate which is converted into coloured end product
D. Requires RBCs

Answer

### Step-by-Step Solution for ELISA

1. **Understanding ELISA**: ELISA stands for Enzyme-Linked Immunosorbent Assay. It is a plate-based assay technique used for detecting and quantifying proteins, antibodies, hormones, and peptides.

2. **Principle of ELISA**: The main principle behind ELISA is the interaction between antigens and antibodies. In this assay, the target antigen is immobilized on a plate.

3. **Addition of Antibodies**: After the antigen is immobilized, a primary antibody is added. This antibody binds specifically to the target antigen, forming an antigen-antibody complex.

4. **Enzyme Conjugation**: The primary antibody is linked to an enzyme. This enzyme plays a crucial role in the next step of the assay.

5. **Substrate Addition**: A suitable substrate is added to the plate. The enzyme linked to the primary antibody reacts with this substrate, resulting in a color change.

6. **Color Change as Detection**: The color change indicates the presence and quantity of the target antigen. This is the key outcome of the ELISA process.

7. **Evaluating the Options**:
- **Option 1**: "Uses complement-mediated cell lysis" - Incorrect, as ELISA does not involve cell lysis.
- **Option 2**: "Uses radiolabeled second antibody" - Incorrect, as ELISA typically does not use radiolabeled antibodies.
- **Option 3**: "Involves addition of substrate which is converted into colored end product" - Correct, as this is a fundamental part of the ELISA process.
- **Option 4**: "Requires RBC" - Incorrect, as red blood cells are not required for ELISA.

8. **Conclusion**: The correct answer is **Option 3**: "Involves addition of substrate which is converted into colored end product."