Immunoglobulin synthesis by neoplastic cells: models of a clonal transition from IgM to IgG synthesis

Tumour populations from two B cell neoplasms were investigated for their capacity to synthesise immunoglobulin in vitro. Neoplastic cells from a patient with chronic lymphocytic leukaemia and an IgG lambda paraproteinaemia co-expressed surface IgG lambda and IgM lambda and synthesised both IgG lambda and IgM lambda in short-term culture. In the second patient with non-Hodgkin's lymphoma, the neoplastic cells expressed surface IgM lambda but synthesised both IgM lambda and IgG lambda in vitro. The findings are discussed in terms of a model for the clonal switch from IgM to IgG synthesis.