Development of a non-radioactive endpoint in a modified local lymph node assay

A murine local lymph node assay (LLNA) has been developed as an alternative to guinea pig models for contact sensitization testing. Although the LLNA appears to be a little less sensitive than the most stringent of guinea pig assays, it provides a rapid, objective, quantitative and cost-effective me thod for screening strong contact sensitizers and has advantages with respe ct to animal welfare. However, a potential disadvantage is the need for the use of radioactive material. We have reported previously that an ex vivo a ssay based on similar principles to the original in vivo LLNA, but using a non-radioactive endopoint, was Valid for the prediction of strong sensitize rs. This el viva assay was not sensitive enough to allow prediction of mode rately potent ones. In this study, we propose a new parameter, Corrected IL -2 Index (CII), for the prediction of moderate sensitizers. To obtain CII, the IL-2 release in the supernatant of the cell culture is corrected for ly mph node weight ratio and ratio of CD4-positive subset. We found that CII p redicted the allergenicity of moderate sensitizers, including the ones reco mmended by the OECD in guideline 406, such as mercaptobenzothiazole and hex yl cinnamic aldehyde. The allergenicity of metal salts, such as potassium d ichromate, ammonium tetrachloroplatinate and cobalt chloride, was also pred icted by the CII. We conclude that the use of CII as an index significantly increases the sensitivity of the es vivo method so that moderate sensitize rs may also be detected. (C) 1998 Elsevier Science Ltd. All rights reserved .