[Protein-A plaque test and ELISA: comparison of the two methods for the analysis of B-cell function]

The in vitro analysis of B-cell function has become more important recently. For this purpose, polyclonal B-cell activators (PBAs) and adequate test systems are now available. We compared the protein A plaque assay which is applied to determine the number of immunoglobulin(Ig)-secreting cells and the ELISA (enzyme linked immunosorbent assay) which is employed for the measurement of the amounts of secreted Ig. The number of Ig-secreting cells and the amounts of Ig in the culture supernatants after stimulation of mononuclear cells with PBAs correlated significantly, i.e. a B-cell activation can be detected by both test systems. The variation coefficients of the protein A plaque assay were higher than those of the ELISA. Furthermore, the protein A plaque assay is a very time-consuming method; therefore, an ELISA should be applied for the routine diagnostic of immunodeficiencies. Nevertheless, the protein A plaque assay remains important for the research of immunopathological diseases and for the determination of in vivo activated B-cells (spontaneous plaques) which can increasingly be observed in immunological disorders like AIDS (acquired immunodeficiency syndrome) or systemic lupus erythematosus.