A rapid and simple method of cell labeling by stable conjugation with fluorescein or
rhodamine is described. Viable cells are incubated under benign conditions (near
physiologic pH in normal media) with free fluorescein or tetramethyl rhodamine
isothiocyanate, and are adequately separated from unreacted fluorochrome by washing or
centrifugation through fetal calf serum. The effects of the pH, the time and temperature of
incubation, and the concentration of cells, fluorochrome, and free protein in the media are …