Question

1a. An ELISA is designed in the following way; protein from bacteria of the genius salmonella are attached to the bottom of a well. After the protein has adhered to the well a drop of patients serum with e placed in the well. After 10minutes the well will be washed and the secondary antibody (that has an enzyme attached to it) will then be added. What are you trying to determine about the patient.

Answer 1

ELISA : ELISA is one of the most widely used bio-chemical analysis to investigate the quantitative assessment of an antigen/protein/biomolecule present in a sample. As a general procedure of ELISA, a plate is coated either with antigen/antibody against which an antibody/antigen is to be investigated. The plate (wells) is incubated with the samples and allowed to incubate. Then after washing with an appropriate wash buffer, the primary/secondary antibody duly attached with an enzyme is added. When the substrate for this enzyme is added, the enzyme catalyzes coversion of substrate to a colored product whose absorbance is stoichimetrically equivalent to the concentration of antigen/antibody present in the sample.

In the example given in the question, the serum sample from the pateint is incubated with a protein collected from salmonella and after incubation and washing, a secondary antibody is added. This confirms that the protein with which the wells were coated was actually an antigen produced by the salmonells and the sample of the patient was expected to contain an antibody against it. This is why a secondary antibody attached to an enzyme was added in later stage.

AIM OF THE EXPERIMENT: So, based upon the above information, it is clear that as an investigation aim, the present experiment was designed to analyse presence of anti-salmonella protein/antigen antibodies in the patient in order to analyse his immune response against salmonella infection.