Bridging phenomena in steroid immunoassays. The effect of bridge length on sensitivity in enzyme immunoassay.

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Abstract
The effect of the bridge heterologous combination between antiserum and enzyme-labeled antigen on sensitivity in enzyme immunoassay for 11-deoxycortisol has been investigated. In order to obtain evidence for the bridge length effect, the sensitivity of an assay system using a .beta.-galactosidase-labeled antigen prepared from an 11-deoxycortisol derivative having a carboxy-methylthio moiety as a bridge at C-4 was compared with that in the case of a derivative with an N-(carboxymethyl)carbamoylmethylthio moiety at C-4. The enzyme labeling of 11-deoxycortisol was carried out by the N-succinimidyl ester method. These anti-11-deoxycortisol antisera elicited in rabbits by immunization with different immunogens were used. It was found that the use of the shorter bridge for enzyme labeling resulted in an increase in sensitivity. This indicates that the bridge length is an important factor influencing the sensitivity of enzyme immunoassay.