A rosette assay detects binding by counting cells surrounded by attached red blood cells, producing a flower-like cluster. The attached red cells act as visible binding probes; their coating and the receptor being tested determine what a particular assay measures. A rosette is therefore a measured binding arrangement, not by itself a unique cell identity.
A classic uncoated-sheep-red-cell assay was used to study human lymphocytes. In 1972, Joseph Wybran and colleagues reported rosette-forming cells in blood and thymus, using their distribution as evidence for a thymus-associated population. The blood measurements in 50 normal participants ranged from to under the study conditions.[ref]
The Human Rosette-Forming Cell as a Marker of a Population of Thymus-Derived Cells by Joseph Wybran and others. Abstract, sheep erythrocyte rosettes and participant range
A different design coats red cells with defined complement fragments. In a 1982 experiment, an antibody against Mac-1 inhibited iC3b-dependent rosetting while selected other receptor-mediated binding remained intact. Comparing coatings and inhibition conditions helped connect the binding phenotype to complement receptor 3.[ref]
Anti-Mac-1 selectively inhibits the mouse and human type three complement receptor by D. I. Beller and others. Abstract, selective inhibition of rosetting
For a constructed count, 60 rosette-positive cells among 200 evaluable cells gives . The scoring threshold, denominator and preparation conditions must accompany that percentage: changing what counts as a cluster can change the reported result.
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