A simple method to detect complement receptors using baker's yeast: Y C rosettes.
A technique is described to identify complement-receptor-bearing cells, using serum-treated baker's yeast as a ligand. The method consists of incubation of heat-killed baker's yeasts with fresh AB normal serum, freezing, thawing, and washing of the particles, followed by mixing with the cells. Serum is required to coat the yeasts for the rosette formation. Experiments designed to establish the serum factors responsible for the attachment of the particles to cells show that heat inactivation, chelating agents, or anti-C3 treatment prevent rosette formation. This is taken as evidence that yeasts (Y) are coated with complement (C) to compose the reagent for the YC rosette technique. The application of this technique to twenty-five normal individuals demonstrated that a mean of 11.6 per 100 lymphocytes (+/- 4.3) form rosettes; absolute number: 275 (+/- 160) rosette-forming lymphocytes per mm3. Either AB or autologous fresh serum can be used to coat the yeasts. A combined technique for YC plus E rosettes can be performed allowing the identification and enumeration of four populations of lymphocytes: (a) those having receptors for sheep erythrocytes, (b) complement-receptor-bearing lymphocytes, (c) those having both receptors (D lymphocytes), and (d) non-rosette-forming non-phagocytic cells.