A novel and sensitive method for the detection of secreted cell products using time-resolved fluorescence

A new test has been developed for the quantitative detection of products secreted from isolated cells, based on the use of lanthanide- rather than enzyme-linked streptavidin. Used as a label, europium (Eu3+) can be measured with high sensitivity by time-resolved fluorescence. The main advantages of this assay are both an increased sensitivity and measuring range of cell released substances, when compared to the standard "wet" ELISA. Thus, the immunoglobulin secretion rate of 10(5) splenocytes could be easily measured by time-resolved fluoroimmunoassay (TR-FIA), while it remained below the detection limit of the 'wet' ELISA. In contrast to the classical ELISPOT test, this assay does not detect single antibody secreting cells (ASC), but would be useful for precise quantification of secreted cell products, such as immunoglobulins, cytokines, growth factors.