Plural immunoglobulin synthesis in a single cell: an ultrastructural study of two cases with three M-proteins.

Electrophoresis revealed two cases of malignant lymphoma that each contained three M-proteins (IgM lambda.lgG kappa.lgG lambda and IgM lambda.IgM kappa.lgG kappa) in the sera. To determine cellular origin of each M-protein, atypical lymphoid and plasmacytoid cells of both cases were examined by electron microscopy. Atypical lymphoid and plasmacytoid cells possessed rough endoplasmic reticula (RERs) in varying degrees, as seen by conventional electron microscopy, and showed double-stainability for plural antibodies against immunoglobulins following double stainings of immunoelectron microscopy using immunogold staining. Rabbit antibodies against human IgM, lgG, free kappa-light chain and free lambda-light chain were used for the immunoelectron microscopic staining. By the double staining method, plural immunoglobulins, IgM/IgG, IgM/free kappa, IgM/free lambda, IgG/free kappa, IgG/free lambda and free kappa/free lambda, were simultaneously detected in varying degrees in the Golgi area, RERs, and dense bodies of lymphoid and plasmacytoid cells. In conclusion, this study directly exhibited, through electron microscopy, that plural immunoglobulins were synthesized at the same time in a single cell, and that the process of immunoglobulin synthesis in the lymphoid and plasmacytoid cells was different from that in a normal B-cell.