Staphylococcal protein A; its preparation and an application to rubella serology.

Good yields of staphylococcal protein A are obtained by growing the staphylococcus Cowan type 1 on cellophane agar. The activity of these preparations in removing immunoglobulin G (IgG) from human serum can be readily measured by the Mancini radial-diffusion technique and the correct in-use dilution determined. Treatment with protein A of sera from women with a history of rubella may help in the identification of those having specific antibody in the IgM and IgA fractions. This relatively simple procedure may have worthwhile application in the diagnosis of rubella.