Anti-Human IgG3 polyclonal antibody [HRP]

In activated B cells, increased production of phosphatidylcholine (PtdCho), the most abundant cellular phospholipid, is handled primarily by the CDP-choline pathway. B cell-specific deletion of CTP: phosphocholine cytidylyltransferase alpha (CCT alpha), the rate-limiting enzyme in the CDP-choline pathway, led to augmented IgM secretion and reduced IgG production, suggesting that PtdCho synthesis is required for germinal center reactions. To specifically assess whether PtdCho influences B cell fate during germinal center responses, we examined immune responses in mice whereby PtdCho synthesis is disrupted in B cells that have undergone class switch recombination to IgG1 (referred to as either C gamma 1(wt/wt), C gamma 1(Cre/wt) or C gamma 1(Cre/Cre) based on Cre copy number). Serum IgG1 was markedly reduced in naive C gamma 1(Cre/wt) and C gamma 1(Cre/Cre) mice, while levels of IgM and other IgG subclasses were similar between C gamma 1(Cre/wt) and C gamma 1(wt/wt) control mice. Serum IgG2b titers were notably reduced and IgG3 titers were increased in C gamma 1(Cre/Cre) mice compared with controls. Following immunization with T cell-dependent antigen NP-KLH, control mice generated high titer IgG anti-NP while IgG anti-NP titers were markedly reduced in both immunized C gamma 1(Cre/wt) and C gamma 1(Cre/Cre) mice. Correspondingly, the frequency of NP-specific IgG antibody-secreting cells was also reduced in spleens and bone marrow of C gamma 1(Cre/wt) and C gamma. 1(Cre/Cre) mice compared to control mice. Interestingly, though antigen-specific IgM B cells were comparable between C gamma 1(Cre/wt), C gamma 1(Cre/Cre) and control mice, the frequency and number of IgG1 NP-specific B cells was reduced only in C gamma 1(Cre/Cre) mice. These data indicate that PtdCho is required for the generation of both germinal center-derived B cells and antibody-secreting cells. Further, the reduction in class-switched ASC but not B cells in C gamma 1(Cre/wt) mice suggests that ASC have a greater demand for PtdCho compared to germinal center B cells. (C) 2016 Elsevier Inc. All rights reserved.

Hypervirulent Klebsiella pneumoniae (hvKp) strains are predicted to become a major threat in Asia if antibiotic resistance continues to spread. Anticapsular antibodies (Abs) were developed because disseminated infections caused by hvKp are associated with significant morbidity and mortality, even with antibiotic-sensitive strains. K1-serotype polysaccharide capsules (K1-CPS) are expressed by the majority of hvKp strains. In this study, K1-CPS-specific IgG Abs were generated by conjugation of K1-CPS to immunogenic anthrax protective antigen (PA) protein. Opsonophagocytic efficacy was measured in vitro and in vivo by intravital microscopy in murine livers. In vivo protection was tested in murine models, including a novel model for dissemination in hvKp-colonized mice. Protective efficacy of monoclonal antibodies (MAbs) 4C5 (IgG1) and 19A10 (IgG3) was demonstrated both in murine sepsis and pulmonary infection. In hvKp-colonized mice, MAb treatment significantly decreased dissemination of hvKp from the gut to mesenteric lymph nodes and organs. Intravital microscopy confirmed efficient opsonophagocytosis and clearance of bacteria from the liver. In vitro studies demonstrate that MAbs work predominantly by promoting FcR-mediated phagocytosis but also indicate that MAbs enhance the release of neutrophil extracellular traps (NETs). In anticipation of increasing antibiotic resistance, we propose further development of these and other Klebsiella-specific MAbs for therapeutic use.