Characterization of IgD. II. Molecular forms of IgD in human B cells

Endogenous and surface labelling techniques were used on human lymphoid cells to characterize intracytoplasmic, membrane and secreted IgD. IgD synthesized by lymphocytes and inserted into the cell membrane displayed a single molecular form with the same mobility in sodium dodecyl sulphase polyacrylamide gel electrophoresis (SDS-PAGE) as the previously described slow migrating serum IgD1. Plasma cells produced and secreted IgD1 and another IgD corresponding to the faster-moving serum IgD2. Conversion of one molecular form into the other was never observed, thus indicating that neither molecule is a precursor or a degradation product of the other.