Synthesis of IgE by the human conceptus

The capability of the human conceptus in synthesizing IgE was investigated in this study. Embryonic and fetal tissues obtained from spontaneously or therapeutically aborted conceptuses were cultured in the presence of ¹⁴C-labeled amino acids, and the culture fluids were then analyzed by radioimmunoelectrophoresis for the presence of radioactive IgE and IgG. Synthesis of IgE was noted as early as 11 weeks in fetal lung and liver, and by 21 weeks in fetal spleen. Interestingly, synthesis of IgG was also found as early as 11 weeks of gestation. The data indicate: (1) that the conceptus has the potential, in terms of IgE synthesis, for developing reaginmediated sensitivity in utero; and (2) that each of the immunoglobulin classes of man may be synthesized by separate lymphoid cell lines rather than from a single cell line that develops immunoglobulin synthesis sequentially.