A new method for semi-automated quantitation of E-rosettes using a particle size analyser (Coulter Channelyzer).

Visual counts of the number of SRBC attached to individual lymphocytes in E-rosette preparations from 3 healthy young adults were made by 3 experienced observers: from these data the size distribution profile of particles in each E-rosette preparation was calculated. In parallel experiments the size distribution profile was measured directly with a particle size analyser (Coulter Counter and Channelyzer): in every case the observed profile lay within the 95% confidence band around the reconstructed profiles. It was concluded that the Coulter Channelyzer profile is an accurate measurement of the E-rosette size distribution and that particle sizing could provide a reasonable basis for semi-automated tests for E-rosettes. A mathematical model has been developed by which the percentage of lymphocytes forming E-rosettes, the distribution of number of attached SRBC and the average avidity of the lymphocyte receptor for SRBC could be deduced from the size-distribution profiles. The method has a high degree of precision, and a good correlation (P less than 0.01) was obtained when the percentage of E-rosettes (defined for this purpose as having three or more attached SRBC) obtained from the new method was compared with results from standard light microscopy.