Which Fc receptor-bearing cells are detected with the Ripley assay?

Mononuclear cells were isolated from peripheral blood and analysed with T and B markers (E rosettes and SIg) and on contaminating monocytes and PMN. The suspensions contained 63.3 +/- 4.8% T lymphocytes, 11.4 +/- 3.8% B lymphocytes, 9.0 +/- 5.5% null lymphocytes, 15.1 +/- 3.8% monocytes and 1.1 +/- 0.6% PMN. Of all cells, 27.6 +/- 12.1% formed EA rosettes with OR1R2 red cells coated with anti-CD Ripley. In preparations fixed after cytocentrifugation, the EA rosette-forming cells were studied with regard to esterase activity. The proportion of cells with detectable Fc receptors was further studied in purified T lymphocyte and in monocyte suspensions. Finally, EA rosettes were isolated by gradient centrifugation and the rosette forming cells studied with conventional T and B markers. All procedures gave corresponding results: on average 11-14% of the T lymphocytes and nearly 100% of the null cells formed EA rosettes, while only 2% of the B lymphocytes had detectable Fc receptors. Of the purified monocyte and PMN populations, on average 72 +/- 10.5 and 14.5 +/- 5.4%, respectively, formed EA rosettes. Thus, the Ripley assay, representing an important marker for null lymphocytes, cannot be regarded as specific for this population of white blood cells.