The Virtual Immunology Laboratory
DIAGNOSIS OF DISEASE BASED ON IMMUNE RESPONSE—A VIRTUAL LABORATORY EXERCISE
Components of the immune system called antibodies
are found in the liquid portion of blood and help protect the body
from harm. Antibodies can be used also outside the body in a
laboratory-based assay to help diagnose disease caused by
malfunctions of the immune system or by infections.
This virtual laboratory will demonstrate how such a test, termed an enzyme-linked immunosorbent assay (ELISA), is carried out and some of the key experimental problems that may be encountered. Students will learn about the assay procedure and the equipment and materials that are needed. By completing this exercise, students will gain a better understanding of experimental design, key concepts in immunological reactions, and interpretation of data.
The basis of humoral immunity
The foundation for ELISA
Potential errors in conducting an ELISA
Sensitivity and specificity of a diagnostic test
Potential Experimental Problems
ELISA is used in many laboratories to determine whether a particular antibody is present in a patient's blood sample. Although the procedure is routine and straightforward, it involves a number of variables, such as reagent selection, temperature, volume measurement, and time, which if not adjusted correctly can affect subsequent steps and the test outcome. This virtual laboratory has been developed so that when a mistake is made, you will not get the correct answer. The program keeps track of errors made throughout the experiment and generates a report at the end.
Limitations of the Test
This general test has some important limitations.
First, a positive result correctly confirming the presence of
antibody does not necessarily mean the patient is sick. The body can
continue to produce antibodies even though the person may have had
the disease earlier and recovered.
Second, people may be poor producers of antibody or may have some interfering substance in their blood. The amount of antibody, consequently, may be too low to measure accurately or may go undetected. This result is termed a false negative.
Third, a positive result may occur if an unrelated antibody reacts with the antigen nonspecifically. Unlike a true-positive result where the specific antibody is detected, however, this positive reaction is false. Testing many patients and running tests more than once helps lab workers distinguish a true from a false result. To avoid simple experimental mistakes leading to incorrect results, scientists conduct tests using duplicate (or, sometimes, more than two) samples.
Begin with the Background describing the experiment.
Find out the antibody concentration of a test antiserum and the number of antibody binding sites on an antigen molecule.
Rubella Radial Haemolysis
advise patients about a dangerous virus.
Mr. Campbell's Kidney
Perform the most popular laboratory test (ELISA) in the world today.