Detection of soluble type II receptor in the presence of its natural ligand XXXX . Quantification by sandwich ELISA.

@entity10732 @entity1356
The type II interleukin-1 receptor ( @entity10732 ) is a newly described 60-68 kDa protein expressed on monocytes, neutrophils, and lymphocytes. It is hypothesized that a 45 kDa soluble form of the @entity10732 attenuates the proinflammatory effects of IL-1 by preventing its binding to the type I IL-1 receptor. However, very little information exists regarding the detection of soluble @entity10732 . Specifically, there are no reports to date characterizing @entity10732 detection by enzyme-linked immunoassay in the presence of @entity1356 or characterizing @entity1356 detection in the presence of @entity10732 . This study addresses the detection and quantitation of @entity10732 and @entity1356 by a number of sandwich ELISA formats and characterizes the sensitivity of detection in the presence of competitive cytokines. We generated two distinct @entity10732 sandwich ELISAs that can detect receptor down to a level of 50 pg/ml. One, M22/R2, detects only unbound @entity10732 and the other, M2/R2, detects both bound and unbound @entity10732 . In this context, a 4:1 molar ratio of @entity1356 to @entity10732 interferes with the @entity10732 detection by the M22/R2 but not the M2/R2 ELISA. Conversely, @entity10732 at physiologically relevant concentrations interferes with the detection of @entity1356 by three distinct @entity1356 ELISA formats. Taken together, these studies suggest that when measuring samples that may contain both @entity1356 and @entity10732 , careful attention must be given to assay specificity.
