This was discounted by histological studies of intestinal tissues from normal 564+/+ mice that revealed no evidence of primary lesions, although there was lymphomatous infiltration in Peyer’s patches of one case that was characterized by massive splenic and nodal involvement. lymphomas and enhanced susceptibility to bacterial infections. Microarray analyses and serological studies suggested that lymphomagenesis might be related to chronic B-cell activation promoted by IL-21. Strikingly, mice treated continuously with antibiotic-supplemented water did not develop lymphomas or abscesses and exhibited less autoimmunity. This mouse model may help us understand the reasons for enhanced susceptibility to lymphoma development exhibited by humans with a variety of autoimmune diseases, such as Sj?gren syndrome, systemic lupus erythematosus, and highly active rheumatoid arthritis. Systemic lupus erythematosus (SLE) is a severe, multigenic autoimmune disease associated with high serum levels of a variety of autoantibodies directed to nucleic acids and self-antigens. Immune complexes formed by autoantibodies and their targets are deposited in glomeruli, frequently resulting in lethal renal impairment. A number of efforts to understand this pathology have used mouse strains expressing immunoglobulin transgenes with B-cell receptor (BCR) specificities for nucleic acids or other antigens recognized by autoantibodies from patients with SLE.1 One of these mouse strains, termed 564Igi, bears targeted insertions of the heavy (VHDHJH) and light (VJ) chain genes of the pathogenic autoantibody 564 that reacts with single-stranded DNA, single-stranded RNA, and nucleosomes when expressed on a nonautoimmune C57BL/6 (B6) background.2, 3, 4 Recent studies focused on 564Igi mice heterozygous for the 564 heavy and light chain insertions at both loci, that we will Splitomicin term 564+/? mice, showed that B cells from these mice underwent receptor editing, failed to respond to BCR cross-linking or stimulation with lipopolysaccharide, and had large amounts of idiotype-positive serum IgG antibodies, autoantibodies, including antinuclear antibodies (ANAs), and renal disease. Interestingly, production of these antibodies was largely dependent on Toll-like receptor 7 (TLR7).5 The importance of TLR7 to autoimmunity and autoantibody production is also evidenced by strains overexpressing TLR76, 7, 8, 9 and inhibition of autoimmune disease by a TLR7 inhibitor.10 In addition, it was found that a polymorphism of TLR7 in humans identified by the Genome Wide Association Study is a risk factor for development of SLE.11, 12 A link between heightened expression of TLR7 and autoimmunity has been associated with high-level expression of the cytokine, IL-21, which is critical to the autoimmune diseases of BXSB.mice,13 type I diabetes mellitus,14 Splitomicin autoimmune uveitis,15 and collagen-induced arthritis,16 among others. Recently, high-level expression of IL-21 was shown to be critical to the development of mature B-cell lineage lymphomas in Swiss Jim Lambert (SJL) mice.17 In?addition, IL-21 has been associated with the development of a range of human B-cell neoplasms, including Hodgkin disease,18, 19, 20 multiple myeloma,21, 22 chronic lymphocytic leukemia,23 Waldenstrom macroglobulinemia,24 and angioimmunoblastic T-cell lymphoma.17, 18 Finally, increased expression of IL-21 and its receptor, IL-21R, has been documented for autoimmune disorders with increased risk for lymphoma development, including SLE, Sj?gren syndrome, and highly active rheumatoid arthritis.25, 26, 27, 28 Herein, we describe studies of mice homozygous for the?564Igi heavy and light chain insertions that we will term 564+/+ mice. These mice exhibited hypergammaglobulinemia with high levels of serum ANA and antiCdouble-stranded DNA (dsDNA) antibodies from early in life but had no clinically significant renal pathology. Unexpectedly, the mice developed a high incidence of post-germinal center (GC) B-cell lymphomas and exhibited increased susceptibility to bacterial infections. Remarkably, mice treated with oral antibiotics to deplete gut flora not only did not develop infections, Mouse monoclonal to CD14.4AW4 reacts with CD14, a 53-55 kDa molecule. CD14 is a human high affinity cell-surface receptor for complexes of lipopolysaccharide (LPS-endotoxin) and serum LPS-binding protein (LPB). CD14 antigen has a strong presence on the surface of monocytes/macrophages, is weakly expressed on granulocytes, but not expressed by myeloid progenitor cells. CD14 functions as a receptor for endotoxin; when the monocytes become activated they release cytokines such as TNF, and up-regulate cell surface molecules including adhesion molecules.This clone is cross reactive with non-human primate but were also lymphoma free and had fewer autoimmune manifestations. This model may be useful for further dissecting long-suspected ties between autoimmunity and lymphomagenesis as well as contributions of gut microbiota to lymphomas and autoimmune disease. Materials and Methods Mice Breeding pairs of 564Igi mice heterozygous for knockin alleles of the 564 IgH and IgK (herein termed 564+/? mice) were obtained from Dr. Theresa Imanishi-Kari (Tufts University, Boston, MA). The 564+/? mice were crossed to generate mice homozygous for the knockins at both loci (herein termed 564+/+ mice). Some members of the 564+/+ mouse colony were bred and maintained on water supplemented with Splitomicin 1 mg/mL ampicillin (Sigma, St. Louis, MO), 1 mg/mL metronidazole (Sigma), 1 mg/mL neomycin (Sigma), and 500 g/mL vancomycin (Hospira, Lake Forest, IL). The 564+/+, 564+/?, BXSB.values were determined by one- or two-way analysis of Splitomicin variance, as appropriate. Results Histopathology Studies of 564Igi Mice Most previous studies of mice bearing the 564 Ig heavy (IgH) and (Ig) chain knockins were performed with animals heterozygous for both alleles (564+/?). We elected Splitomicin to study mice homozygous for both alleles at both loci (564+/+). During the course of this study, we observed moribund mice as young as 2.5 months of age with no obvious cause of morbidity, whereas others exhibited periorbital infections, splenomegaly, or lymphadenopathy. Fifty-three mice were necropsied, with 30 of the moribund mice listed in Table?3. Histopathology findings revealed that 19 of these mice had hematopoietic neoplasms, mostly affecting spleen and.