Further investigation of the light chain shifting phenomenon: light chain replacement through secondary rearrangement induced by lectin stimulation in the hybridoma cell line HB4C5.

We found that when the hybridoma cell line HB4C5 was stimulated with wheat germ agglutinin (WGA), loss of production of the original lambda light chain occurred, followed by production of new light chain, which mirrored the reaction when stimulated with concanavalin A (ConA). We previously reported that the RAG genes are expressed not only in HB4C5 and its ConA-treated variant subclones, but also in the in the parental Namalwa cells, which are known to be in the plasma state. However, the new lambda light chains were expressed only in the HB4C5 cells and not in the parental Namalwa cells. Here we found that the RAG genes are expressed in HB4C5 cells after continuous stimulation with WGA. To further investigate the mechanism of this loss of original lambda light chain production by stimulation with lectins in HB4C5 cells, which leads to a sIg-negative subpopulation, we analyzed the differences between HB4C5 and Namalwa cells. In this present study, we found that a 70 kDa phosphorylated protein in HB4C5 cells became undetectable after stimulation with lectins (WGA and ConA), and was not detected in Namalwa cells before or after lectin stimulation. It has been believed that the RAG genes and loss of original lambda light chain production are required to induce expression of a new lambda light chain in the HB4C5 cells. We suggested that the phosphorylated 70 kDa protein in HB4C5 cells play important roles in regulating the production of new lambda light chains which is induced by lectins.