Induction of balanced immunoglobulin chain synthesis in free light chain-producing lymphocytes by mitogen stimulation.

Neoplastic cells from 2 cases of CLL synthesized and secreted excess free Ig light chain in culture, confirmed by precipitation with anti-idiotypic antibody. Small and medium sized normal human spleen cell subpopulations, staining predominantly for surface IgM and D, also synthesized and secreted excess free light chain. PWM stimulation induced balanced synthesis of heavy and light chains in CLL and normal spleen subpopulations after 6 days in culture, accompanied in spleen but not CLL by the appearance of mature plasma cells. These data demonstrate that normal cell counterparts of neoplastic lymphoid synthesis patterns can be identified in spleen. Furthermore, the synthesis pattern alteration after PWM stimulation suggests a relationship between free light chain synthesis and B cell immaturity. The failure of CLL cells to develop into detectable plasma cells suggests a restricted maturation response to mitogen compared with normal spleen.