The ability to isolate, characterise and recombine, in a predetermined manner, immunologically reactive cells is one of the most powerful tools with which to investigate the detailed workings of the immune network. However, the study of cell affinity chromatography centres on the cell rather than on the technique. Hence, none of the systems, with the notable exception of the fluorescence-activated cell sorter, have been subjected to extensive technological innovation. There is an obvious need for a greater characterisation of the criteria by which cells are fractionated to to improve reproducibility. These essentially biophysical techniques could then serve as a basis for defining the cell type isolated. This would remove the need to define the isolated cell only in terms of the pre-existing lymphocyte subjects, which rarely correspond directly. © 1978.