B cells from p50/NF-κB knockout mice have selective defects in proliferation, differentiation, germ-line C_H transcription, and Ig class switching

Abstract

To better understand the role of NF-κB in normal B cell physiology, we used a purified population of resting B cells from p50/NF-κ B knockout (p50^(-/-)) mice to determine their ability to proliferate, secrete Ig, express germ-line C_H RNA, and undergo Ig isotype switching in vitro in response to a number of distinct stimuli. p50^(-/-) B cells proliferated normally in response to dextran-anti-IgD Abs (αδ-dex) and membrane-bound, but not soluble, CD40 ligand (CD40), and they were virtually unresponsive to LPS when compared with control B cells. p50^(-/-) B cells secreted markedly reduced Ig in response to αδ-dex or mCD40L in the presence of IL-4 + IL-5, despite their relatively normal proliferative rates, whereas normal Ig secretion was restored by the combination of αδ-dex and CD40L. p50^(-/-) B cells expressed normal steady-state levels of germ-line C_Hγ1 and C_Hα RNA but markedly reduced germ-line C_Hγ3 and C_Hϵ RNA upon appropriate stimulation. Although p50^(-/-) B cells underwent substantial switching to IgG1, a marked reduction in the switch to IgG3 and IgE, as IgA, was observed. These data are the first to demonstrate key, independent roles for p50/NF-κB in normal B cell maturation to Ig secretion, germ-line CH gene activation, and Ig class switching, as well as mitogenesis, and provide a powerful and well-defined in vitro model system for studying the role of p50/NF-κB in a wide range of normal cellular functions.