Identification of Cell Surface Immunoglobulin Markers by Protein A‐Containing Fluorescent Staphylococci

Abstract
We describe a simple method for detecting surface‐associated IgG on some human lymphoid cell lines and on mouse lymphocytes. using fluorescent Staphylococcus aureus (strain Cowan 1). The adherence of the fluorescent bacteria to cell surface‐located IgG is mediated by protein A (SpA) molecules on the bacterial cell wall. Inhibition of the adherence of bacteria by soluble SpA was used for quantitation of IgG on cell surface. The method has a good specificity and a high sensitivity and detects approximately 600 IgG molecules per cell.