Comparative Study of Membrane and Intracytoplasmic Immunoglobulin Classes in Human Lymphoid Cells*

Immunofluorescent and "in vitro" biosynthetic techniques have been used to study the connections between the maturation process of human lymphocytes that leads to the appearance of actively secreting cells and a possible switchover from IgD to IgM production, both in homogeneous CLL cell populations and in heterogeneous cell suspensions from tonsils. The results obtained are compatible with the hypothesis that the switchover from IgD to IgM productions can be a clonal maturation phenomenon.