BNS k in the Absence of I Impaired B Cell Development and Function

I k BNS has been identified as a member of the I k B family of NF- k B inhibitors, which undergoes induction upon TCR signaling. Mice carrying a targeted gene disruption of I k BNS demonstrate dysregulation of cytokines in T cells, macrophages, and dendritic cells. I k BNS mediates both positive and negative gene regulation, depending on individual cell type and/or cytokine. In this study, we demonstrate an additional role for I k BNS in the B cell lineage. B cells from I k BNS knockout (KO) mice were impaired in proliferative responses to LPS and anti-CD40. IgM and IgG3 Igs were drastically reduced in the serum of I k BNS KO mice, although I k BNS KO B cells exhibited a higher level of surface IgM than that found in wild-type mice. Switching to IgG3 was significantly reduced in I k BNS KO B cells. The in vitro induction of plasma cell development demonstrated that progression to Ab-secreting cells was impaired in I k BNS KO B cells. In agreement with this finding, the number of Ab-secreting cells in the spleens of I k BNS KO mice was reduced and production of Ag-specific Igs was lower in I k BNS KO mice after influenza infection as compared with wild-type mice. Additionally, I k BNS KO mice lacked B1 B cells and exhibited a reduction in marginal zone B cells. Thus, I k BNS significantly impacts the development and functions of B cells and plasma cells. The Journal of Immunology , 2011, 187: 000–000. B cells were purified from splenocytes of WT and I k BNS KO mice by positive selection of B220-expressing cells using anti-B220–conjugated MACS magnetic beads (Miltenyi Biotec). T cells were purified from lymph nodes of WT mice by depleting B cells with anti-B220–conjugated magnetic beads. FACS analysis with B220, CD4, and CD8 staining showed that B cell preparations contained . 98% B220 + cells, whereas T cell preparations contained . 95% CD4 + and CD8 + cells. The purified B cells from WT and I k BNS KO mice were mixed with T cells from WT mice (1 3 10 7 each) and injected i.v. into rag-2 2 / 2 mice. The reconstituted mice were challenged with 75 m g alum-precipitated TNP-KLH given i.p. 24 h after the transfer. Serum was collected every 7 d after immunization, and the spleen was harvested on day 14 postimmunization.