What are some of the lessons learnt from in vitro studies of severe unpredictable drug reactions?

Diagnosis of drug hypersensitivity: lymphocyte transformation test and cytokines

For all types of allergic reactions including immediate type of reactions, types II and III reactions as well as delayed-type reactions the recognition of the antigen by specifically sensitized T-lymphocytes is a prerequisite. Evidences for the key role of T-lymphocytes in the pathophysiology of allergic drug reactions are positive patch test reactions and the LTT. The proliferative response that can be measured by means of the incorporation of 3H-thymidine during DNA synthesis can be expressed as stimulation index (SI) which is the relation between the cell proliferation with antigen compared without antigen. In addition drug-specific activation of PBMC consistently resulted in IL-5 expression and secretion. The sensitivity of the LTT for the detection of drug sensitization could be improved up to 92% by the measurement of released interleukin-5. The expression and secretion of other cytokines such as IFN-gamma and IL-10 was less consistently and had a diagnostic sensitivity of 36 and 50%, respectively. Microarrays are a promising new technical platform to look for better markers which can be used as a read out in the LTT and other similar assays and to study pharmacological interactions between drugs including cytokines such as interferons and the immune system.

Determination of interleukin-5 secretion from drug-specific activated ex vivo peripheral blood mononuclear cells as a test system for the in vitro detection of drug sensitization

BACKGROUND

In vitro detection of drug sensitization is still limited. The lymphocyte transformation test, which determines drug-specific proliferation, is the only in vitro test for detecting drug sensitization at the cellular level irrespective of the reaction's clinical phenotype. Accumulation of eosinophils following IL-5 secretion from drug-specific stimulated T cells is a characteristic histological feature of drug-induced skin eruptions.

OBJECTIVE

We determined whether in vitro drug-specific activation of ex vivo peripheral blood mononuclear cells from 10 patients with drug-induced maculopapular exanthems and three patients with severe skin reactions results in secretion of IL-5, IL-10 or IFN-gamma and assessed the sensitivity and specificity of drug-specific IL-5 secretion as a test system compared with the lymphocyte transformation test and patch tests. Furthermore, the subsets of CD4+ and CD8+ T cells involved in drug-specific proliferation, IL-5 secretion and mRNA expression were examined in three patients.

METHODS

Drug-specific proliferation of peripheral blood mononuclear cells in the lymphocyte transformation test was investigated by 3H-thymidine uptake, and culture supernatants taken after 5 days were analysed for IL-5, IL-10 and IFN-gamma concentrations by ELISA technique. IL-5 mRNA expression was determined by RT-PCR.

RESULTS

Drug-specific activation of peripheral blood mononuclear cells consistently resulted in IL-5 and to a lesser extent in IL-10 and IFN-gamma secretion. The sensitivities of the patch test, lymphocyte transformation test and assessment of drug-specific IL-5 secretion for the detection of drug sensitization were 55%, 75% and 92%, respectively.

CONCLUSION

These data suggest a role for the determination of drug-specific IL-5 secretion by ex vivo peripheral blood mononuclear cells for the in vitro detection of drug-sensitization in drug-induced maculopapular exanthems.