DIAGNOSIS OF DRUG ALLERGY BY THE LYMPHOCYTE STIMULATION TEST WITH THEMTT [3-(4,5-DIMETHYL THIAZOL-2-YL)-2,5-DIPHENYL TETRAZOLIUM BROMIDE] ASSAY

The lymphocyte stimulation test (LST) is one of the most useful labora tory tests for the identification of allergy to a specific drug. The p resent study was conducted to examine utility of the LST using the [3- (4,5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] (MTT) a ssay as a method for diagnosing drug allergy. The basic experimental c onditions for the MTT assay were determined by using CTLL cells from h uman T-lymphoma, dependent on IL-2, and human peripheral blood lymphoc ytes. The amount of MTT needed was 0.5 mg per well and the peak maximu m of MTT formazan was close to 565 nm. The blastogenesis of the lympho cytes was expressed as a Stimulation Index (SI). The value of the SI w as almost constant at cell numbers ranging from 5 x 10(5) to 1 x 10(6) cells/ml. The SI of some drugs using normal peripheral blood lymphocy tes was less than 1.3. We used the MTT assay in the LST to examine the allergenicity of 83 drugs which were used in 43 cases of suspected dr ug-induced hepatitis. The range of SI was 0.92-2.02. An SI of 1.2 or m ore was seen in 62.8% of cases, 1.3 or more in 51.2% of cases, and 1.4 or more in 41.9% of cases. There were 26 drugs with SI greater than 1 .3. Seven of these were antibiotics, while the rest included antihyper tensives, analgesics, psychotropics, antiallergics and antiepileptics. This method is extremely well suited for the diagnosis of drug allerg y in a clinical situation. The greatest benefit of the MTT assay is th at the complete test procedures can be carried out in a general labora tory.