A plaque assay to enumerate circulating Ig-secreting cells of each type of the different Ig classes

A new method to quantitate circulating cells secreting immunoglobulin (Ig) of each type of the different classes by hemolytic plaque technique is reported. The ratio of kappa (k)-secreting cells and lambda(lambda)-secreting cells of the different lg classes in normal individuals is almost equal to that of kappa:lambda light chains in corresponding serum lg class, whereas the ratio in plasma cell myeloma patients is extraordinarily high or low, indicative of the type and class specificity of this assay system as well as the monoclonal nature of circulating Ig-secreting cells in such patients.