Gel microdroplets and flow cytometry: rapid determination of antibody secretion by individual cells within a cell population.

We report a new method capable of rapidly determining the secretion of biologically important macromolecules from each of many individual cells within a large population. This method combines flow cytometry with gel microdroplets (GMDs), which in this study were agarose particles ranging from about 53 to 88 mu in diameter. The GMDs were formed from a liquid 2.5% agarose suspension with cells at a concentration which yielded mostly zero or one cell per GMD. A large number of extracellular binding sites were also provided within each GMD, allowing the capture of secreted molecules, and their subsequent measurement by solid phase, fluorescence immunoassay. The method was explored using a model system of mouse hybridoma (secreting) and mouse masticytoma (non-secreting) cells. The method was able to determine subpopulations of individual cells that secreted antibody in less than fifteen hours after receipt of a conventional cell suspension.