A SIMPLE, RAPID, AND SENSITIVE SCINTILLATION PROXIMITY ASSAY FOR THE DETERMINATION OF LEVELS OF GUINEA-PIG INTERLEUKIN-5 IN BRONCHOALVEOLARLAVAGE SAMPLES

This article describes the development and validation of a scintillati on proximity assay (SPA) sensitive for guinea-pig interleukin-5 (IL-5) . SPA beads were coated with TRFK-5, a monoclonal antibody directed ag ainst mouse IL-5, which is known also to bind guinea-pig IL-5. The ass ay is a simple competitive binding assay between [I-125]-rh-IL-5 and t he IL-5, in a sample of guinea-pig bronchoalveolar lavage fluid (BALF) , for the binding site on the TRFK-5-coated beads. IL-5 levels in BALF ([IL-5](BALF)) were shown to increase in guineapigs sensitized to ova lbumin (OvA) and challenged with an OvA inhalation. This occurred at a time (24 h) after challenge when there was also a marked eosinophilia . The assay was validated by treating guinea-pigs with a second antibo dy, Genzyme 2374-01, directed against IL-5. Treatment with this antibo dy resulted in a significant reduction of the antigen-induced eosinoph ilia and concentration of [IL-5](BALF). This observation confirms that the IL-5 identified in BALF also cross-reacts with the antibody Genzy me 2374-01. Interestingly, plasma from sensitized, but unchallenged, g uinea-pigs also contained detectable levels of IL-5, and the stimulati on of plasma protein extravasation (PPE) within the airways with inhal ed histamine also induced a rise in [IL-5](BALF). These observations s uggest that the plasma may be an additional source of the IL-5 present in the airways of antigen-challenged guinea-pigs. (C) 1997 Elsevier S cience Inc.