IMMUNOGLOBULIN PRODUCED BY GUINEA-PIG LEUKEMIC LYMPHOCYTES-B - ITS SOURCE AND USE AS A MONITOR OF TUMOR LOAD

Abstract

The cells of the B lymphocytic leukemia (L2C) of strain 2 guinea-pigs have IgM on their surfaces but produce insufficient monoclonal IgM in vivo to be detectable by conventional serum electrophoresis. A radioimmunoassay, using anti-idiotypic antibody raised against the surface IgM of these cells, was used to estimate levels of extracellular IgM produced in vitro and in vivo. Analyses of the contributions to such IgM from the cell surface and from an export pathway were made by examining the effect of prior removal of surface Fab.mu. by papain, and by following the fate of radio-iodinated surface IgM. The extracellular IgM probably arises predominantly from an export pathway, being exported in pentameric and monomeric forms. Only a minute contribution, possibly in the form of vesicle-bound monomeric IgM, appears to derive from the cell surface. Radioimmunoassay was used to monitor the increasing levels of this leukemic cell product during the course of the disease. Idiotypic IgM was detectable when the body load of neoplastic cells was approximately 4% of that detectable by an increased white cell count in the blood.