Immunofluorescent diagnosis of acute lymphoblastic leukaemia.

When leukaemic lymphoblasts from acute lymphatic leukaemia were reacted with animal anti-human lymphocyte globulin (AHLG), and subsequently with the appropriate, fluorescein-isothiocyanate-conjugated antibodies, a brilliant membrane fluorescence was observed, which persisted up to 5 log titres, breaking from rings into spots at higher dilutions. The best results were obtained with fresh suspensions and incident illumination. Cross-reactions with mature and immature myeloid cells with the unabsorbed antisera could be abolished by repeated preabsorbtion of AHLG with packed leukocyte preparations from chronic and acute myeloid leukaemias. Thus, it appears that this approach is susceptible of improving the identification of leukaemic lymphoblasts, and may be extended, by means of appropriate antisera, to the acute leukaemias in general.