Rapid loss of IgM expression by normal murine B cells undergoing IgG1 and IgE class switching after in vivo immunization
Snapper, C.M.; Finkelman, F.D.
Journal of Immunology 145(11): 3654-3660
1990
ISSN/ISBN: 0022-1767 PMID: 2147198 Document Number: 358994
Injection of mice with polyclonal goat anti-mouse IgD antibody (G.alpha.M.delta.) stimulates a potent T cell-dependent immune response characterized by large increases in serum IgG1 and IgE concentrations and by the generation of substantial numbers of membrane (m)IgG1+ B cells. The onset of this response occurs 6 days after G.alpha.M.delta. injection and peaks by day 7 to 8. Utilizing two color fluorescence analysis and cell sorting we demonstrate that most mIgG1-expressing B cells lack mIgM during the period of onset of Ig isotype switching (day 6). Both IgG1 and IgE are produced predominantly by mIgM- cells. On day 6, IgG1 and IgE are secreted predominantly by cells expressing mIgG1 and mIgE, respectively. By day 8, a majority of the IgG1 secretion occurs among the mIgG1- cells but virtually all IgE secretion continues to come from the mIgE+ population. B cells that strongly express mIgG1 secrete little IgM or IgE. Freshly harvested B cells expressing mIgG1, 6 days after G.alpha.M.delta. injection, have undergone substantial deletion of CH.mu.-specific DNA in contrast to their mIgG1- counterparts. Hence, the great majority of B cells that switch to the IgG1 or IgE isotypes in vivo rapidly lose their expression of IgM.