EXPRESSION OF THE IMMUNOGLOBULIN J-CHAIN IN A MURINE B-LYMPHOMA IS DRIVEN BY AUTOCRINE PRODUCTION OF INTERLEUKIN-2

Expression of the immunoglobulin J chain is initiated by lymphokine si gnals delivered to activated B cells during a primary immune response, In the mature murine B cell line, CH12.LX, IL-5 and LPS but not IL-2 were found to greatly enhance basal levels of J chain gene expression, Analysis of the IL-2 receptor (IL-2R) showed two defects: an unusuall y low expression of the IL-2R alpha chain and little or no IL-2R beta chain, Treatment with IL-5 strongly amplified IL-2R alpha chain expres sion in CH12.LX cells, yet failed to confer IL-2 responsiveness, Howev er, when the IL-2R beta chain was introduced by stable transfection, t he cells expressed 400-500 high affinity IL-2R and responded to IL-2 w ith increased J chain expression, Surprisingly, in the absence of exog enous lymphokine stimulation, the basal levels of J chain and IL-2R al pha in all IL-2R beta transfectants became significantly elevated over time, Analysis showed that CH12.LX cells constitutively synthesized I L-2 and, given a functional IL-2R, responded to the lymphokine in an a utocrine fashion to upregulate both J chain and IL-2R alpha. Thus, CH1 2.LX cells provide a model cell line in which the role of the IL-2R be ta chain in differentiative events such as J chain upregulation can be examined. (C) 1996 Academic Press Limited