Measurement of antigen specific lymphocyte proliferation using 5-bromo-deoxyuridine incorporation. An easy and low cost alternative to radioactive thymidine incorporation.

The classical in vitro assay for the determination of cell mediated immune responses is the lymphocyte transformation test (LTT) in which cell proliferation is measured by incorporation of radioactive labeled thymidine (3H-TdR). The LTT assay using 3H-TdR is less suited for modestly equipped laboratories as it is costly, laborious and involves the need to handle radioactive isotopes and specialized equipment. Here we describe an improved alternative LTT method which is capable of detecting specific cellular immune reactions (CMI) against (mycobacterial) antigens in vitro. This assay, the bromodeoxyuridine-ELISA LTT test, is simple, less expensive, reproducible and is as sensitive as the 3H-TdR test. The specific advantages of the test are a simple denaturation step and the fact that no radioactive isotopes are needed. The test is specifically suited for research laboratories in tropical countries which study CMI in those human infectious diseases where this arm of the immune response plays a pivotal role in the generation of immunity, e.g., in tuberculosis, leprosy and leishmaniasis.