The MHC class I-like Fc receptor FcRn plays an essential role in extending the half-life (t1/2) of IgG antibodies and IgG-Fc-based therapeutics in the circulation. The goal of this study was to ...analyze the effect of human IgG1 (hIgG1) antibodies with enhanced in vitro binding to FcRn on their in vivo t1/2 in mice expressing human FcRn (hFcRn). Mutants of the humanized monoclonal Herceptin antibody (Hu4D5-IgG1), directed against human epidermal growth factor receptor 2 (p185 HER2), show altered pH-dependent binding to hFcRn in vitro. Two engineered IgG1 mutants (N434A and T307A/E380A/N434A) showed a considerably extended t1/2 in vivo compared with wild-type antibody in mice expressing an hFcRn transgene (Tg) but not in mice expressing the endogenous mouse FcRn. The efficiency of hFcRn-mediated protection was dependent on hFcRn Tg copy number. Moreover, when injected into FcRn-humanized mice at a concentration sufficient to partially saturate hFcRn, the engineered IgG1 mutants with an extended serum t1/2 were most effective in reducing the t1/2 of a tracer hIgG1 antibody. Finally, administration of mutant with high binding to hFcRn ameliorated arthritis induced by passive transfer with human pathogenic plasma. These results indicate that Fc regions modified for high binding affinity to hFcRn increases serum persistence of therapeutic antibodies, that the same approach can be exploited as an anti-autoimmune therapy to promote the clearance of endogenous pathogenic IgG and that FcRn-humanized mice are a promising surrogate for hIgG therapeutic development.
The inverse relationship between serum albumin concentration and its half-life suggested to early workers that albumin would be protected from a catabolic fate by a receptor-mediated mechanism much ...like that proposed for IgG. We show here that albumin binds FcRn in a pH dependent fashion, that the lifespan of albumin is shortened in FcRn-deficient mice, and that the plasma albumin concentration of FcRn-deficient mice is less than half that of wild-type mice. These results affirm the hypothesis that the major histocompatibility complex-related Fc receptor protects albumin from degradation just as it does IgG, prolonging the half-lives of both.
Abs of the IgG isotype are efficiently transported from mother to neonate and have an extended serum t(1/2) compared with Abs of other isotypes. Circumstantial evidence suggests that the MHC class ...I-related protein, the neonatal FcR (FcRn), is the FcR responsible for both in vivo functions. To understand the phenotypes imposed by FcRn, we produced and analyzed mice with a defective FcRn gene. The results provide direct evidence that perinatal IgG transport and protection of IgG from catabolism are mediated by FcRn, and that the latter function is key to IgG homeostasis, essential for generating a potent IgG response to foreign Ags, and the basis of enhanced efficacy of Fc-IgG-based therapeutics. FcRn is therefore a promising therapeutic target for enhancing protective humoral immunity, treating autoimmune disease, and improving drug efficacy.
Most studies of vascular disease in transplanted organs have used combinations involving disparities determined by genes of the major histocompatibility complex (MHC). This report describes examples ...of coronary vascular disease occurring in transplanted mouse hearts involving isolated, non-H2-determined incompatibilities.
Mice, incompatible in respect of HY, H4, or H60, were selected. For H60, the incompatibility depended on breeding congenic pairs or the introduction of H60 by transgenic methods because the latter method results in more widespread expression. Transplant survival was determined, and the appearance and prevalence of coronary artery vasculopathy (CAV) was established by appropriate histologic methods.
Advanced changes of CAV were found at 56 days in transplants involving incompatibilities confined to HY or H4. In both combinations, skin grafts were also rejected. H60 incompatibility does not result in skin graft rejection and only a minority of heart transplants shows evidence of CAV. If heart transplants are preceded by skin grafts bearing both H60 and HY incompatibilities to promote "help" in generating immunity, H60 incompatible hearts develop advanced CAV. Heart transplants in all non-MHC categories ostensibly survive in excellent condition throughout this period despite their CAV.
CAV can develop as a consequence of non-MHC incompatibilities alone and even when antigens are sparsely expressed on cardiac tissue. Presensitization leads to much more severe vascular disease. Human leukocyte antigen compatible kidney transplants may also develop vascular disease and patients manifesting reactivity to MHC antigens should also be more prone to develop vascular disease because of undetectable non-MHC incompatibilities.
The neonatal crystallizable fragment receptor (FcRn) functions as an intracellular protection receptor for immunoglobulin G (IgG). Recently, several clinical studies have reported the lowering of ...circulating monomeric IgG levels through FcRn blockade for the potential treatment of autoimmune diseases. Many autoimmune diseases, however, are derived from the effects of IgG immune complexes (ICs). We generated, characterized, and assessed the effects of SYNT001, a FcRn-blocking monoclonal antibody, in mice, nonhuman primates (NHPs), and humans. SYNT001 decreased all IgG subtypes and IgG ICs in the circulation of humans, as we show in a first-in-human phase 1, single ascending dose study. In addition, IgG IC induction of inflammatory pathways was dependent on FcRn and inhibited by SYNT001. These studies expand the role of FcRn in humans by showing that it controls not only IgG protection from catabolism but also inflammatory pathways associated with IgG ICs involved in a variety of autoimmune diseases.
Homologues of the SHARPIN (SHANK-associated RH domain-interacting protein) gene have been identified in the human, rat and mouse genomes. SHARPIN and its homologues are expressed in many tissues. ...SHARPIN protein forms homodimers and associates with SHANK in the post-synaptic density of excitatory neurotransmitters in the brain. SHARPIN is hypothesized to have roles in the crosslinking of SHANK proteins and in enteric nervous system function. We demonstrate that two independently arising spontaneous mutations in the mouse Sharpin gene, cpdm and cpdm(Dem), cause a chronic proliferative dermatitis phenotype, which is characterized histologically by severe inflammation, eosinophilic dermatitis and defects in secondary lymphoid organ development. These are the first examples of disease-causing mutations in the Sharpin gene and demonstrate the importance of SHARPIN protein in normal immune development and control of inflammation.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
IL-21 is a type I cytokine whose receptor is expressed on T, B, and NK cells. Within the B cell lineage, IL-21 regulates IgG1 production and cooperates with IL-4 for the production of multiple Ab ...classes in vivo. Using IL-21-transgenic mice and hydrodynamics-based gene delivery of IL-21 plasmid DNA into wild-type mice as well as in vitro studies, we demonstrate that although IL-21 induces death of resting B cells, it promotes differentiation of B cells into postswitch and plasma cells. Thus, IL-21 differentially influences B cell fate depending on the signaling context, explaining how IL-21 can be proapoptotic for B cells in vitro yet critical for Ag-specific Ig production in vivo. Moreover, we demonstrate that IL-21 unexpectedly induces expression of both Blimp-1 and Bcl-6, indicating mechanisms as to how IL-21 can serve as a complex regulator of B cell maturation and terminal differentiation. Finally, BXSB-Yaa mice, which develop a systemic lupus erythematosus-like disease, have greatly elevated IL-21, suggesting a role for IL-21 in the development of autoimmune disease.
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Interleukin‐21 (IL‐21) is a pleiotropic cytokine whose function is only now being unraveled. Abundant evidence indicates that activated CD4 T cells are the primary, if not the only, source of ...IL‐21. While it is clear that IL‐21 is actively transcribed by naïve activated T cells, recent studies have shown that IL‐21 potentially promotes a developmental shift of naïve T cells toward the Th2 phenotype. BXSB‐Yaa mice develop an autoimmune syndrome similar to systemic lupus erythematosus (SLE), affecting males earlier than females on account of the presence of the Yaa (Y‐linked autoimmune acceleration) locus. Previous results indicate the elevation of IL‐21 expression by BXSB‐Yaa mice at an age when the early characteristics of autoimmune processes first become evident. We set out to determine whether IL‐21 was necessary for disease progression in BXSB‐Yaa mice. Mice were treated for 24 weeks with soluble IL‐21R‐Fc in order to therapeutically neutralize the IL‐21 present. The results overall suggest a biphasic effect of IL‐21, negatively influencing survival early on and positively influencing survival at later stages. We propose that IL‐21 exerts a pleiotropic effect in which it promotes the protective effects of CD8+ suppressor cells in the early disease phase and then promotes the humoral components of SLE in the later disease stages. This experiment provides preliminary evidence for a role of IL‐21 in modulating the severity of SLE in BXSB‐Yaa mice.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Periodontal disease affects a large percentage of the human population. Resorption of the alveolar bone of the jaw is a pivotal sequela of periodontal disease, because this bone is the attachment ...site for the periodontal ligaments that anchor the teeth. Using a murine model in which alveolar bone loss is induced by oral infection with Porphyromonas gingivalis, a gram-negative bacterium associated with human adult periodontal disease, we provide evidence suggesting that susceptibility to such bone loss is a genetically determined trait. AKR/J, DBA/2J, and BALB/cByJ or BALB/cJ mice were highly susceptible, while A/J, A/HeJ, 129/J, SJL/J, and C57BL/6J mice were much more resistant. When susceptible BALB/cJ and BALB/cByJ mice were crossed to resistant strains, two patterns were observed. (BALBc/ByJ x C57BL/6J)F(1) offspring were susceptible, suggesting C57BL/6J has recessive resistance alleles, while (BALB/cJ x A/J)F(1) mice were all resistant, suggesting that A/J mice have dominant resistance alleles. These results suggest a tractable genetic basis for P. gingivalis-induced alveolar bone loss and open the possibility of exploiting the mouse model to identify loci important for host susceptibility and resistance to periodontal disease.
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