ELISA plaque assay for the detection of antibody secreting cells: observations on the nature of the solid phase and on variations in plaque diameter.

This report examines the basis for variations in the size and number of ELISA plaques detected in vitro. The nature and concentration of antigen used to coat the solid phase is shown to be critical, high concentrations of polymerized antigen being optimal for low molecular weight proteins, while coating conditions for high molecular weight multideterminant antigens are similar to conventional liquid ELISA. Variations in plaque diameter are shown to reflect maturational changes in the immune response, and probably indicate differences in the affinity of antibody being secreted within a population of plasma cells.