Lymphocyte proliferative response to drugs: Analysis of the value of a 24-well lymphocyte culture system

The aim of this study was to analyse the value of a 24-well lymphocyte culture system in the detection of lymphocyte sensitization to drugs in 19 patients with drug-induced liver injury and 19 healthy controls. Lymphocytes responses to drugs under suspicion were assessed in vitro by [ 3H]thymidine incorporation in the lymphocytes. The responses observed in cultures with and without the drug were compared using Student's t-test for the analysis of significance of differences. Data were also analysed to calculate estimates of the frequency of drug-specific T cells by Poisson sampling statistics. The mean and the standard deviation (SD) of the cpm in the 24-well ‘negative’ cultures (without drug) were determined. A cut-off for negative results, corresponding to the mean plus 2SD, was established. Negative wells (lower than the cut-off) were counted in the ‘positive’ cultures (cultures with drug) and the Poisson mean (PM) was determined as follows: PM = natural logarithm of number of wells tested/number of negative wells. The results were compared with those observed using a triplicate culture system in the same patients. In 14 out of 19 cases studied, significant differences between the means of lymphocyte cultures with and without drug were observed, whereas in the triplicate system, reactivity was found only for nine cases. In all cases in which more than one drug was tested, lymphocyte sensitization was detected to only one drug. No positive cases were detected in the group of healthy controls. The estimated precursor frequencies varied between 0.3 and 1.3 per 100,000 cells. The results represent further evidence that drug-specific T cells exist in the peripheral blood of patients with drug-induced liver injury and justifies a more extensive analysis of the value of the 24-well culture system from a diagnostic point of view.