Comparison of activation and blocking procedures in the use of defined antigen substrate spheres (DASS) for quantitative and visual assessment of conjugate activity

The use of Sepharose beads in the defined antigen substrate sphere (DASS) immuno-fluorescent system has been restricted by the need for sophisticated equipment for fluorescence quantitation since reliable subjective reading is not possible. This paper describes a method for visual assessment of results in this system. Antigen is coupled to sodium metaperiodate activated cross-linked Sepharose 4B beads and blocked with rhodamine-BSA prior to reduction. This procedure eliminates the use of the hazardous cyanogen bromide activation process and is potentially suitable for use in both direct systems for evaluation of specificity and potency of fluorescent conjugates and in indirect systems for serological screening of sera for specific antibody.