Inflammatory bowel disease (IBD) is a chronic inflammatory disease thought to be mediated by dysfunctional innate and/or adaptive immunity. This aberrant immune response leads to the secretion of harmful cytokines that destroy the epithelium of the gastrointestinal tract leading to further inflammation. IL-22 is a Th17 T cell associated cytokine that is bi-functional with both pro-inflammatory and protective effects on tissues depending on the inflammatory context. We show herein that IL-22 protects mice from IBD. Interestingly, this protection is not only mediated by CD4 T cells, but IL-22 expressing NK cells also confer protection. In addition, IL-22 expression is differentially regulated between NK cell subsets. Thus, both the innate and adaptive immune responses have developed protective mechanisms to counteract the damaging effects of inflammation on tissues.

Significance The accompanying paper describes the precise, in situ replacement of six megabases of mouse immune genes with the corresponding human immune genes. This manuscript shows that this genomic engineering feat resulted in a unique kind of “HumAb” mouse. Dubbed VelocImmune, these mice efficiently generate antibodies that can be rapidly reformatted into therapeutics. VelocImmune mice have proven to be extraordinarily efficient and productive, generating over a dozen therapeutic candidates that have already progressed into human clinical trials for a variety of important diseases.

Differentiation and recruitment of alternatively activated macrophages (AAMacs) are hallmarks of several inflammatory conditions associated with infection, allergy, diabetes, and cancer. AAMacs are defined by the expression of Arginase 1, chitinase-like molecules, and resistin-like molecule (RELM) α/FIZZ1; however, the influence of these molecules on the development, progression, or resolution of inflammatory diseases is unknown. We describe the generation of RELM-α–deficient (Retnla−/−) mice and use a model of T helper type 2 (Th2) cytokine-dependent lung inflammation to identify an immunoregulatory role for RELM-α. After challenge with Schistosoma mansoni (Sm) eggs, Retnla−/− mice developed exacerbated lung inflammation compared with their wild-type counterparts, characterized by excessive pulmonary vascularization, increased size of egg-induced granulomas, and elevated fibrosis. Associated with increased disease severity, Sm egg–challenged Retnla−/− mice exhibited elevated expression of pathogen-specific CD4+ T cell–derived Th2 cytokines. Consistent with immunoregulatory properties, recombinant RELM-α could bind to macrophages and effector CD4+ Th2 cells and inhibited Th2 cytokine production in a Bruton's tyrosine kinase–dependent manner. Additionally, Retnla−/− AAMacs promoted exaggerated antigen-specific Th2 cell differentiation. Collectively, these data identify a previously unrecognized role for AAMac-derived RELM-α in limiting the pathogenesis of Th2 cytokine-mediated pulmonary inflammation, in part through the regulation of CD4+ T cell responses.

Genetic humanization, which involves replacing mouse genes with their human counterparts, can create powerful animal models for the study of human genes and diseases. One important example of genetic humanization involves mice humanized for their Ig genes, allowing for human antibody responses within a mouse background (HumAb mice) and also providing a valuable platform for the generation of fully human antibodies as therapeutics. However, existing HumAb mice do not have fully functional immune systems, perhaps because of the manner in which they were genetically humanized. Heretofore, most genetic humanizations have involved disruption of the endogenous mouse gene with simultaneous introduction of a human transgene at a new and random location (so-called KO-plus-transgenic humanization). More recent efforts have attempted to replace mouse genes with their human counterparts at the same genetic location (in situ humanization), but such efforts involved laborious procedures and were limited in size and precision. We describe a general and efficient method for very large, in situ, and precise genetic humanization using large compound bacterial artificial chromosome-based targeting vectors introduced into mouse ES cells. We applied this method to genetically humanize 3-Mb segments of both the mouse heavy and κ light chain Ig loci, by far the largest genetic humanizations ever described. This paper provides a detailed description of our genetic humanization approach, and the companion paper reports that the humoral immune systems of mice bearing these genetically humanized loci function as efficiently as those of WT mice.genome engineering | therapeutic antibody | immunoglobulin locus T he laboratory mouse is one of the premier model organisms used by biologists. As a mammal, the mouse is more genetically similar to humans and thus more relevant to human physiology and disease than many other model organisms. Its small size, short generation time, and the availability of a large variety of inbred strains have led to a robust body of classical genetic research on the mouse. The utility of mice as a genetic model is also greatly enhanced by powerful transgenic and knockout technologies, allowing researchers to study the effects of the directed overexpression or deletion of specific genes. However, despite all of its advantages, the mouse remains an imperfect model of human disease and an imperfect platform on which to test potential human therapeutics. One issue is that, although about 99% of human genes have a mouse homolog (1), potential therapeutic agents often do not cross-react, or cross-react only poorly, with the mouse ortholog of the intended human target. To overcome this problem, selected target genes can be humanized, that is, the mouse gene can be eliminated and replaced by the corresponding human orthologous gene sequence. Because of the difficulties of using conventional KO technologies to directly replace large mouse genes with their large human genomic counterparts, genetic humanization is currently mo...

OCA-B was initially identified as a B-cell-restricted coactivator that functions with octamer binding transcription factors (Oct-1 and Oct-2) to mediate efficient cell type-specific transcription of immunoglobulin promoters in vitro. Subsequent cloning studies led to identification of the coactivator as a single polypeptide, designated either as OCA-B (ref. 3), OBF-1 (ref. 4) or Bob-1 (ref. 5). OCA-B itself does not bind to DNA directly, but interacts with either Oct-1 or Oct-2 to potentiate transcriptional activation. To determine the biological role of OCA-B, we generated OCA-B-deficient mice by gene targeting. Mice lacking OCA-B undergo normal antigen-independent, B-cell differentiation, including appropriate expression of both immunoglobulin genes and other early B-cell-restricted genes. However, antigen-dependent maturation of B cells is greatly affected. The proliferative response to surface IgM crosslinking is impaired, and there is a severe deficiency in the production of secondary immunoglobulin isotypes including IgG1, IgG2a, IgG2b, IgG3, IgA and IgE in OCA-B-deficient B cells. This defect is not due to a failure of the isotype switching process, but rather to reduced levels of transcription from normally switched immunoglobulin heavy-chain loci. In accord with the defective isotype production, germinal centre formation is absent in these mutant mice.