In vitro T-cell responses to beta-lactam drugs in immediate and nonimmediate allergic reactions

Background: beta -Lactam drugs may induce both cellular and humoral allergi c reactions, and there is evidence that T cells play an important role in t he pathogenesis of these reactions. The aim of this work was to assess the sensitivity and specificity of the lymphocyte transformation test (LTT) as an in vitro diagnostic tool, in patients with either an immediate or a noni mmediate reaction to penicillin G and/or amoxicillin. Methods: Fifty patients with a well-documented history of allergic reaction s to beta -lactams (31 immediate and 19 nonimmediate) were studied by means of skin tests (prick and intradermal), radioallergosorbent test (RAST), an d, when necessary, controlled administration of the drug. Twenty-eight heal thy subjects with good tolerance to penicillins served as controls. LTT was performed in all subjects. Results: Skin tests were positive in 77.4% of the patients with immediate r eactions and in 36.8% of those with nonimmediate reactions. The overall sen sitivity of LTT in the allergic patients was 62%, but, when analyzed separa tely, sensitivity was 64.5% for the immediate group and 57.9% for the nonim mediate group. The LTT specificity was 92.8%. Conclusions: The LTT should be considered a useful in vitro diagnostic tool to identify subjects allergic to penicillins, especially patients with non immediate reactions where the LTT has a better diagnostic value than skin t ests. Interestingly, positive T-cell proliferative responses can be observe d 10 or more years after the occurrence of the reaction without further exp osure to the drug.