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D. I. Beller is the first author of a 1982 study relating Mac-1 to a specific function of the complement system. The investigators used an antibody against Mac-1 and a rosette assay, in which appropriately coated red blood cells bind around immune cells. The antibody inhibited binding mediated by the complement fragment iC3b, while selected other receptor-dependent binding remained intact.^[ref]

The controls separated selective inhibition from indiscriminate loss of cell binding. The original conclusion was that Mac-1 was identical to, or closely associated with, the relevant complement-receptor function. A blocking experiment can establish a strong functional association without, by itself, resolving every molecular detail of that association.^[ref]

Joseph Wybran is the first author of a 1972 study investigating a rosette assay as a marker of human lymphocytes associated with the thymus. In the assay, sheep red blood cells surrounded certain human lymphocytes, producing a recognizable cluster that could be counted.^[ref]

The investigators compared blood and developing tissues, finding the highest proportions of rosette-forming cells in the tested thymus samples. They combined those distributions with observations in immune disorders to propose a chiefly thymic origin for the blood population.^[ref]

The important step was connecting a visible binding behaviour to a biological population. Counting clusters is an operational measurement; identifying the cell's origin is an interpretation requiring independent evidence. The historical study supplied evidence for a marker, not a rule that every lymphocyte forms a rosette under every set of assay conditions.

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 $4\%$ to $40\%$ under the study conditions.^[ref]

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]

For a constructed count, 60 rosette-positive cells among 200 evaluable cells gives $60/200=30\%$. The scoring threshold, denominator and preparation conditions must accompany that percentage: changing what counts as a cluster can change the reported result.