[Purification and standardization of commercial fluorescein-containing antiserums]

A method for the improvement of commercial antisera that consist of ammonium sulfate precipitated gamma-globulins labelled with fluorescein isothiocyanate, is presented. By a simple desalting on Sephadex G25 followed by a DEAE-cellulose stepwise chromatography, it is easy to recover only the fluoresceinated immunoglobulins of optimal fluorescein/protein ratio. The aspecificities due to the other fluoresceinated (mainly albumin) and also to the hypo- and hyper-conjugated gamma-globulins are then avoided. Even if eventual defects as regards the intrinsic characteristics of the antisera are not modified by this process, the improvement obtained is stringent and particularly evident in the indirect immunofluorescent staining of tissue sections. In consideration of the excellent quantitative recovery, this simple procedure is recommended to people that use commercial reagents for studies that are beyond the qualitative limits of routine diagnostic immunofluorescent tests.