Question

1. What is the role of the capture antibody in the ELISA?

2. How is a colored reaction product produced in the ELISA?

3. What is the role of the Abeta standard curve in the ELISA?

Answer 1

1. The ELISA technique using Capture Antibody is known as Sandwich ELISA. In this technique an antibody (Capture Antibody) specific to the antigen is added before adding the detection antibody thereby the antigen is 'sandwiched' between the two antibodies and detection by ELISA is done. This technique is usually done for complex samples as it does not require purification before the process. The addition of Capture Antibody increases the Sensitivity and Specificity of the ELISA test. Moreover both direct and indirect ELISA can be used for detection.

2. In ELISA or enzyme linked immunosorbent assay , a detection antibody which is specific to a particular or desired antigen is added to the sample. This detection antibody will be linked to an enzyme. If the desired antigen is present in the sample, the detection antibody will get attached to the antigen. After washing away the remaining antibodies, when a subtrate to the linked enzyme is added a colored reaction product is produced and the colour will be directly propotional to the amount of antigen in the sample.

3. Abeta ELISA is a Sandwich ELISA method to detect Amyloid beta proteins in the sample . The standard curve may be useful in the early detection of Alzeimers Disease by detecting the Amyloid beta or Abeta proteins from the plasma or brain tissue of the patient.