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A model ZBI Coulter Counter was interfaced to an Apple II microcomputer via analog and digital interfaces. It was possible to obtain a graphic display of cell size versus channel number (1000 channels), integration of selected channels, plots, listings, and storage of the data on floppy disk, using a convenient menu selection enabling operators unfamiliar with computer technology to master the system quickly. Examples are presented of calibration of the Coulter Counter and its use for rapid and precise analysis of E rosettes.

An Ia-rosette assay for the detection of Ia-like alloantigens on the chicken lymphoid cell surface is described. The method is based on the ability of cells treated with alloantiserum to Ia and then with rabbit antiserum against the Fc portion of chicken IgG, to form rosettes with sheep erythrocytes (SRBC) coated with chicken anti-SRBC IgG antibody. Interference with Ia-rosette formation by Fc IgG receptors was eliminated by pronase treatment which removes Fc receptor activity without affecting Ia antigens. The Ia-rosette assay is at least as sensitive as the triple-layer immunofluorescence test for identification of Ia antigens. In addition, the assay allows morphological study and separation of the rosetting cells.