Immunoglobulin Expression in Human Lymphoblastoid Cell Lines with Early B Cell Features

Abstract

Ig expression was studied by direct immunofluorescence and by biosynthesis experiments in 2-human cell lines Raji [Burkitts lymphoma] and T 5.1. The basic phenotype of these cells was close to that of pre-B cells: large cells with intracytoplasmic IgM with a predominance of .mu. chains over L chains and no detectable surface Ig. The apparent MW of H and L chains was abnormally large. Ig were secreted at a low rate as pentameric IgM in the T 5.1 line and as subunits and free L chains in the Raji line. Spontaneous variations of this phenotype were observed: the cultured cells acquired surface .mu. and .lambda. chains, then additionally .delta. chains while they progressively lost detectable cytoplasmic .mu. chains, thus leading to a mature B cell phenotype. Subsequently, the cells had no detectable surface and cytoplasmic Ig and then they displayed a pre-B cell phenotype again. Attempts to induce further maturation using various potential inducers were unsuccessful.