Our data demonstrate activation and drug specificity of T cells in drug-induced skin eruptions. A predominant CD8(+) T cell activation leads to more severe (bullous) skin symptoms or liver involvement, while predominant activation of CD4(+) cells elicits mainly maculo-papular reactions.

Background: Macular or maculopapular skin reactions are frequent events in drug allergy as well as in viral infections. Clinically, the differentiation may be difficult in the absence of a clear relationship to drug intake or failure to detect virus–specific antibodies of the IgM class. Studies on drug–specific T cell lines and T cell clones isolated from drug–allergic patients have suggested that these cells may represent a significant source of IL–5. On the other hand, viral infections are frequently associated with elevated IFN–γ levels. Objective: Determination of serum–cytokine levels to differentiate between drug– and virally induced skin eruptions. Patients: 18 patients suffering from acute drug allergy and 19 patients with acute measles, rubella or parvovirus infection. Measurements: Cytokine–ELISA (IL–5, IL–4 and IFN–γ) of sera collected during acute drug allergy or during acute measles, rubella or parvovirus infection. Results: In 12/18 patients with drug allergy, IL–5 and/or IL–4 were elevated. A significant correlation (r_Spearman = 0.84) between IL–5 serum levels and eosinophil counts in the blood was found. No correlation was detected between IL–4 and blood eosinophilia or between IL–4 and IL–5 levels. After remission, IL–5 and IL–4 decreased to undetectable levels. IFN–γ on the other hand was not measurable in patients with drug allergy while elevated IFN–γ serum levels were detected in 17/19 patients with measles, rubella or parvovirus infection; 2 patients with acute virus infection had elevated IL–5, and/or IL–4 and IFN–γ levels. Conclusion: These data underline the distinct pathogenesis of these morphologically similar exanthemas and suggest that the combined analysis of eosinophilia in the blood, IL–4 and IFN–γ might help in differentiating skin eruptions.

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