title: NF-kB inhibitor blocks B cell development at two checkpoints.
abstract: Members of the NF-kB transcription factor family are differentially expressed in the B cell lineage. Disruption of individual or two NF-kB subunits exhibits distinct defects in B lymphocyte development, activation, and survival. However, the role each NF-kB plays during B cell development has been obscured by molecular compensation. To address this issue, a trans-dominant form of IkBalpha was transduced into bone marrow cells to act as a pan-inhibitor of NF-kB using a retroviral system. While the development of T-lymphocytes and myeloid cell lineages was not grossly affected by the transduced IkBalpha gene, a significant reduction in the number and percentage of B lineage cells was apparent in IkBalpha transduced chimeric mice. IkBalpha expression decreased the percentage of pre-B and immature B cell subsets in the bone marrow and further impaired the development of follicular mature B cells and marginal zone B cells in the periphery. Introduction of the Bcl-X transgene completely restored the pre-B and immature B cell pool in the bone marrow. However, despite a significant improvement of overall viability of the B cell lineage, Bcl-X expression was insufficient to overcome the maturation block resulting from NF-kB inhibition. Together, our study suggests that NF-kB activity is required for two distinct checkpoints during B cell development: one is for pre-B/immature B cell viability, the other is to provide both survival and maturation signals to ensure the proper development of follicular mature B cells.
authors.affiliation: Division of Immunology, Department of Medicine, Weill Medical College of Cornell University, New York, NY 10021, USA. hcliou@med.cornell.edu
authors.forename: Biao
authors.initials: B
authors.lastname: Feng
authors.forename: Shuhua
authors.initials: S
authors.lastname: Cheng
authors.forename: Warren S
authors.initials: WS
authors.lastname: Pear
authors.forename: Hsiou-Chi
authors.initials: HC
authors.lastname: Liou