The molecular events that mediate Ig class switching, a process critical for generating a functionally diverse humoral immune response, are poorly understood. A role for NF-kB/Rel transcription factors in switching is suggested by multiple binding sites for these proteins within the Ig heavy chain locus, including promoters, enhances, and switch regions. Thus, NF-kB/Rel proteins might regulate transcriptional events that determine the accessibility of constant heavy (CH) genes for switching, as well as the switching process itself. Indeed, B cells from mice made genetically deficient in p50/NFkB (p50-/-), the transactivation domain of c-Rel (dc-Rel), or RelA/p65 show distinct defects in germline CH RNA expression and/or switch recombination itself. This proposal will determine the 1) functional roles, 2) expression patterns, and 3) mechanism(s) of action of NFkB/Rel proteins in Ig class switching in normal murine B cells in vitro in response to distinct combinations of activators and cytokines. The ability of NF-kB/Rel proteins to regulate Ig isotype selection through modulation of an enhancer complex 3' to Cha (3'aE) and/or I exon promoters, as well as through changes in the cell cycle will be determined. The functions and expression patterns of NF-kB/Rel knockout (KO) and KO/replacement mice activated with anti-lg-dextran, CD40-ligand, and/or LPS +/- multiple cytokines. The locus of action of NF-kB/Rel proteins in germline CH gene expression will be determined using B cells from 3'aE and/or IXSXCX transgenic mice. We will determine the relationships between 1) Ig class switching by flow cytometry and digestion-circularization PCR assays, 2) germline CH RNA levels by RT-PCR, 3) expression of NF-kB/Rel proteins by EMSA immunoblotting, and in vivo footprinting, 4) transgene activation, and 5) DNA synthesis, cell cycle progression, and apoptosis; CFSE labeling will relate division number with Ig isotype expression. These studies will elucidate key parameters that underlie the molecular basis of Ig switching.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Allergy and Immunology Study Section (ALY)
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Quill, Helen R
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Henry M. Jackson Fdn for the Adv Mil/Med
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Horwitz, B H; Zelazowski, P; Shen, Y et al. (1999) The p65 subunit of NF-kappa B is redundant with p50 during B cell proliferative responses, and is required for germline CH transcription and class switching to IgG3. J Immunol 162:1941-6
Vos, Q; Snapper, C M; Mond, J J (1999) Heterogeneity in the ability of cytotoxic murine NK cell clones to enhance Ig secretion in vitro. Int Immunol 11:159-68
Vos, Q; Ortaldo, J R; Conan-Cibotti, M et al. (1998) Phenotypic and functional characterization of a panel of cytotoxic murine NK cell clones that are heterogeneous in their enhancement of Ig secretion in vitro. Int Immunol 10:1093-101
Snapper, C M; Rosas, F R; Kehry, M R et al. (1997) Neisserial porins may provide critical second signals to polysaccharide-activated murine B cells for induction of immunoglobulin secretion. Infect Immun 65:3203-8
Zelazowski, P; Max, E E; Kehry, M R et al. (1997) Regulation of Ku expression in normal murine B cells by stimuli that promote switch recombination. J Immunol 159:2559-62
Zelazowski, P; Carrasco, D; Rosas, F R et al. (1997) B cells genetically deficient in the c-Rel transactivation domain have selective defects in germline CH transcription and Ig class switching. J Immunol 159:3133-9
Snapper, C M; Rosas, F R; Moorman, M A et al. (1997) Restoration of T cell-independent type 2 induction of Ig secretion by neonatal B cells in vitro. J Immunol 158:2731-5
Shparago, N; Zelazowski, P; Jin, L et al. (1996) IL-10 selectively regulates murine Ig isotype switching. Int Immunol 8:781-90
Snapper, C M; Rosas, F R; Zelazowski, P et al. (1996) B cells lacking RelB are defective in proliferative responses, but undergo normal B cell maturation to Ig secretion and Ig class switching. J Exp Med 184:1537-41
Snapper, C M; Rosas, F; Moorman, M A et al. (1996) IFN-gamma is a potent inducer of Ig secretion by sort-purified murine B cells activated through the mIg, but not the CD40, signaling pathway. Int Immunol 8:877-85

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