A simple method for electronic counting of rosette forming human blood lymphocytes.

We investigated the possibility of using a standard electronic laboratory cell counter, of a type which permits manual settings of discriminator and sensitivity levels, for the quantitation of E rosette forming human blood lymphocytes. The electronic counting was performed on rosette specimens prepared from 10 healthy donors, nine lymphoma patients and eight patients with chronic lymphocytic leukaemia (CLL) of B cell type. The simple procedure which was earlier developed for the electronic counting of thymocyte rosettes in guinea-pigs was used and now supplemented with a method for rapid, graphical determination of rosette frequency. The low level of E rosettes in CLL patients was easily distinguished from the higher level seen in the other groups and there was a good agreement between electronic and visual determinations. In samples with a high rosette frequency, the cell counter initially gave 10-30% lower values than when recorded visually. This discrepancy was corrected, however, by a minor adjustment of discriminator level and the introduction of a correction procedure for the presence of double rosettes. We conclude that the electronic counter can well be used for the counting of human rosette forming blood lymphocytes and, due to a high precision and large capacity, this approach would prove to be useful when screening of a large number of samples is required.