The present paper deals with some of the quantitative aspects of immunoglobulin formation in vitro. The results of this study show that isolated spleen cells synthesize about 1.25 μg IgG per 108 lymphoid cells during the first 6 hours of incubation. The initial rate of synthesis was not maintained throughout the 48 hours of incubation, but decreased markedly after 6 hours.
Comparison of the intensity of the autoradiographic line with the amount of radioactive immunoglobulin in the precipitation line revealed that a very distinct line (gradation +++) corresponds to about 0.0125 μg IgG. The limit of visibility (+) is reached at approximately 0.0002 μg radioactive IgG.