Murine plasma cells secreting more than one class of immunoglobulin heavy chain. I. Frequency of two or more M-components in ascitic fluids from 788 primary plasmacytomas.

Primary ascites from 778 consecutive plasmacytomas of BALB/c and other mouse strains were tested by immunoelectrophoresis for the presence of paraproteins belonging to different immunoglobulin classes. gammaA was produced by 338 tumors: gamma Gs (gamma 1, gamma 2a, gamma 2b, or gamma 3) by 163 tumors; and gamma M by seven tumors. Free kappa- or lambda-typed light chains were produced by 14 tumors, and no detectable paraprotein was produced by 202 tumors. Two or more paraproteins were detected in the primary ascites of 54 plasmacytomas. Evidence suggests that in most cases, the multiple paraproteins are produced by simultaneously occurring, independent plasma cell tumors. However, two tumors, SAMM 368 and TEPC 609, produced two paraproteins for over 30 generations in transplantation. This finding implies that single clones of plasma cells have the capacity to produce more than one class of immunoglobulin.