Assay of Immunoglobulins in Supernatants of Lymphoid Cell Lines by Conventional Laser Nephelometry

An adaptation of the nephelometric assay for serum immunoglobulins has been developed for detection and quantitation of extracellular immunoglobulins in cultures of lymphoblastoid cell lines. This assay employs the standard equipment for laser nephelometry and commercial reagents for immunoglobulin quantitation. By adjusting dilutions of controls and sample volumes of culture supernatants, amounts of IgG and IgM below 1 μg/ml can be detected in culture supernatants. At concentrations between 1 and 4 μg/ml, day-to-day and within-run variations for IgM assays were 16 and 11% respectively. The possibility of measuring immunoglobulins secreted by cell lines by conventional laser nephelometry opens several areas of application in the study of the functional activity of B cells and of cell-cell interactions.