Immuno-affinity partition of cells in aqueous polymer two-phase systems.

Poly(ethylene glycol) (PEG) was covalently coupled to IgG antibody preparations directed against human red blood cells. This modification reduces the tendency of the antibody to agglutinate cells and increases its affinity for the upper phase in dextran-PEG aqueous two-phase systems. These effects are related to the molecular weight of the PEG used for modification and to the number of PEG molecules attached to the antibody. Exposure of human red blood cells to PEG-modified antibody causes a substantial and specific increase in cell partition into the PEG-rich phase in a number of PEG-dextran aqueous two-phase systems. Pertinent phase-system parameters were examined. Following a single incubation with PEG-derivatized antibody, a mixture of sheep and human red blood cells was completely separated in 100 min by a 30-transfer countercurrent extraction using a two phase system which normally offers little resolution.