IL-22 regulates lymphoid chemokine production and assembly of tertiary lymphoid organs

The series of events leading to tertiary lymphoid organ (TLO) formation in mucosal organs following tissue damage remain unclear. Using a virus-induced model of autoantibody formation in the salivary glands of adult mice, we demonstrate that IL-22 provides a mechanistic link between mucosal infection, B-cell recruitment, and humoral autoimmunity. IL-22 receptor engagement is necessary and sufficient to promote differential expression of chemokine (C-X-C motif) ligand 12 and chemokine (C-X-C motif) ligand 13 in epithelial and fibroblastic stromal cells that, in turn, is pivotal for B-cell recruitment and organization of the TLOs. Accordingly, genetic and therapeutic blockade of IL-22 impairs and reverses TLO formation and autoantibody production. Our work highlights a critical role for IL-22 in TLO-induced pathology and provides a rationale for the use of IL-22-blocking agents in B-cell-mediated autoimmune conditions.

Th22 cells are an important source of IL-22 for host protection against enteropathogenic bacteria

Interleukin-22 (IL-22) is central to host protection against bacterial infections at barrier sites. Both innate lymphoid cells (ILCs) and T cells produce IL-22. However, the specific contributions of CD4(+) T cells and their developmental origins are unclear. We found that the enteric pathogen Citrobacter rodentium induced sequential waves of IL-22-producing ILCs and CD4(+) T cells that were each critical to host defense during a primary infection. Whereas IL-22 production by ILCs was strictly IL-23 dependent, development of IL-22-producing CD4(+) T cells occurred via an IL-6-dependent mechanism that was augmented by, but not dependent on, IL-23 and was dependent on both transcription factors T-bet and AhR. Transfer of CD4(+) T cells differentiated with IL-6 in the absence of TGF-β ("Th22" cells) conferred complete protection of infected IL-22-deficient mice whereas transferred Th17 cells did not. These findings establish Th22 cells as an important component of mucosal antimicrobial host defense.

IL-22 protects intestinal stem cells from immune-mediated tissue damage and regulates sensitivity to graft vs. host disease (126.31)

Intestinal graft vs. host disease (GVHD) is a major complication of allogeneic bone marrow transplantation (allo-BMT). Strategies to limit GVHD by selective promotion of epithelial regeneration in the absence of immunosuppression are largely unknown. We investigated the role of IL-22 in allo-BMT and found that IL-22 levels in small and large intestine were increased after BMT after radiation injury (RI) without BMT. IL-22 upregulation after RI was dependent on the presence of IL-23p40. Although intestinal IL-22 levels were increased after T cell-depleted (TCD) BMT, intestinal IL-22 was reduced by GVHD, as IL-22 production was mediated by host-derived innate lymphoid cells (ILC) that were eliminated by GVHD. Furthermore, host-derived IL-22 was critical for reduction of GVHD morbidity, mortality, and intestinal pathology. GVHD in IL-22 KO mice led to increased apoptosis in epithelial crypts where the intestinal epithelial stem/progenitor cell niche is located. Immunohistochemistry and immunofluorescence demonstrated IL-22 receptor expression on intestinal stem cells (ISC) and progenitors. Allo-BMT in Lgr5-LacZ reporter mice indicated that ISC were targeted by GVHD, and GVHD in IL-22 KO mice led to dramatic ISC depletion. IL-22 is thus critical for protection of host epithelium during GVHD and critical for protection of ISC. These findings may have broad relevance for protection of ISC and intestinal epithelium in clinical GVHD and other inflammatory intestinal diseases.

Redundant and pathogenic roles for IL-22 in mycobacterial, protozoan, and helminth infections

IL-22 is a member of the IL-10 cytokine family and signals through a heterodimeric receptor composed of the common IL-10R2 subunit and the IL-22R subunit. IL-10 and IL-22 both activate the STAT3 signaling pathway; however, in contrast to IL-10, relatively little is known about IL-22 in the host response to infection. In this study, using IL-22(-/-) mice, neutralizing Abs to IL-22, or both, we show that IL-22 is dispensable for the development of immunity to the opportunistic pathogens Toxoplasma gondii and Mycobacterium avium when administered via the i.p. or i.v. route, respectively. IL-22 also played little to no role in aerosol infections with Mycobacterium tuberculosis and in granuloma formation and hepatic fibrosis following chronic percutaneous infections with the helminth parasite Schistosoma mansoni. A marked pathogenic role for IL-22 was, however, identified in toxoplasmosis when infections were established by the natural oral route. Anti-IL-22 Ab-treated mice developed significantly less intestinal pathology than control Ab-treated mice even though both groups displayed similar parasite burdens. The decreased gut pathology was associated with reduced IL-17A, IL-17F, TNF-alpha, and IFN-gamma expression. In contrast to the prior observations of IL-22 protective effects in the gut, these distinct findings with oral T. gondii infection demonstrate that IL-22 also has the potential to contribute to pathogenic inflammation in the intestine. The IL-22 pathway has emerged as a possible target for control of inflammation in certain autoimmune diseases. Our findings suggest that few if any infectious complications would be expected with the suppression of IL-22 signaling.

Engagement of the PD-1 immunoinhibitory receptor by a novel B7 family member leads to negative regulation of lymphocyte activation

PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor-mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by antigen-presenting cells, including human peripheral blood monocytes stimulated with interferon gamma, and activated human and murine dendritic cells. In addition, PD-L1 is expressed in nonlymphoid tissues such as heart and lung. The relative levels of inhibitory PD-L1 and costimulatory B7-1/B7-2 signals on antigen-presenting cells may determine the extent of T cell activation and consequently the threshold between tolerance and autoimmunity. PD-L1 expression on nonlymphoid tissues and its potential interaction with PD-1 may subsequently determine the extent of immune responses at sites of inflammation.

Continuous venovenous hemofiltration with and without dialysis in pediatric patients

Peritoneal dialysis (PD) is often the preferred modality in dialyzing the pediatric patient in acute renal failure. However, PD may be contraindicated in the presence of the acute surgical abdomen, respiratory compromise, or diaphragmatic disruption. The child's size and cardiovascular instability may also render hemodialysis undesirable. The use of continuous arteriovenous hemofiltration (CAVH) has been an option for the acutely ill child but requires arterial and venous access as well as adequate blood pressure to drive the CAVH circuit. Another option is continuous venovenous hemofiltration (CVVH), which obviates the need for arterial access and provides blood flow via an external pump. This article presents a retrospective of 20 acutely ill pediatric patients who received continuous venovenous hemofiltration with and without dialysis (CVVH/D) during the period covering Fall 1992 through Fall 1993 at Children's Hospital in Seattle. The children ranged in age from 1 day to 12 years (mean age 4 years) and weights ranged from 1.7 kg to 76 kg (mean 15.8 kg). Seventeen of the 20 patients were started on CVVH/D due to hemodynamic instability, 1 for PD complications, and 2 for metabolic disorders. Fluid and solute removal were achieved efficiently and metabolic imbalances were easily corrected. Patients received 1-25 days (mean 7.7 days) of CVVH/D.

Normal and abnormal nephrogenesis

During the past decade, exciting advances in the fields of cell and molecular biology have provided new insight into the processes of normal and abnormal nephron induction and renal morphogenesis. Although the specific molecular signals that control renal mesenchymal-epithelium inductive interaction remain unknown, recent data suggest that postinductive nephrogenesis may be regulated by the overall balance of a number of local autocrine and/or paracrine growth factor systems. Alterations in the critical balance of regulatory factors might produce a variety of hypoplastic and dysplastic nephropathies or hyperplastic lesions such as tubular cysts. Additional studies demonstrate that extracellular matrix components and cell surface integrins have important regulatory roles in ureteric bud development and branching. Perturbations in matrix or integrin expression due to altered gene activity or toxin exposure would be expected to produce a variety of renal abnormalities ranging from failure of nephron induction (aplasia) to focal disruptions of differentiation (segmental dysplasia). Finally, several groups of genes encoding transcriptional regulatory proteins have been identified that appear to regulate aspects of cell proliferation, pattern formation, and segment-specific differentiation during normal and abnormal nephrogenesis. Future studies will elucidate the roles that specific genes and proteins play in renal development and will ultimately reveal the manner in which their dysregulation or dysfunction causes a variety of developmental renal disorders.

Feedback regulation of collagen gene expression: a Trojan horse approach

The mechanisms involved in feedback regulation of type I procollagen synthesis by the N-terminal propeptide of the pro alpha 1(I) chain, termed Col 1, are poorly understood. We have constructed a metallothionein-human collagen chimeric minigene (pMTCol) that codes for a Col 1 fusion protein but lacks a signal peptide sequence and, therefore, would be expected to direct the synthesis of the fusion protein to the cytosol. Baby hamster kidney cells and fetal calf ligament cells, transfected with pMTCol, transcribed the gene and synthesized an intracellular antigen that was identified as the fusion protein with a monospecific antibody. Transfected fetal calf ligament fibroblasts showed significantly reduced levels of endogenously produced type I collagen, as determined by imaging and digital quantitation of immunofluorescence by confocal microscopy; synthesis of fibronectin, thrombospondin, and SPARC (secreted protein, acidic and rich in cysteine) was unchanged or increased in these cells. This recombinant approach offers the potential for a systematic analysis of feedback regulation of collagen synthesis.

Germline mutations in the Wilms' tumor suppressor gene are associated with abnormal urogenital development in Denys-Drash syndrome

Denys-Drash syndrome is a rare human condition in which severe urogenital aberrations result in renal failure, pseudohermaphroditism, and Wilms' tumor (nephroblastoma). To investigate its possible role, we have analyzed the coding exons of the Wilms' tumor suppressor gene (WT1) for germline mutations. In ten independent cases of Denys-Drash syndrome, point mutations in the zinc finger domains of one WT1 gene copy were found. Nine of these mutations are found within exon 9 (zinc finger III); the remaining mutation is in exon 8 (zinc finger II). These mutations directly affect DNA sequence recognition. In two families analyzed, the mutations were shown to arise de novo. Wilms' tumors from three individuals and one juvenile granulosa cell tumor demonstrate reduction to homozygosity for the mutated WT1 allele. Our results provide evidence of a direct role for WT1 in Denys-Drash syndrome and thus urogenital system development.

Transcriptional activity of the alpha 1(I)-collagen promoter is correlated with the formation of capillary-like structures by endothelial cells in vitro

Bovine aortic endothelial (BAE) cells spontaneously form structures in vitro that resemble capillary-like cords or tubes. This process is associated with changes in the expression of certain extracellular matrix proteins that include type I collagen. BAE cells exhibiting angiogenesis in vitro were transfected with plasmids containing either chloramphenicol acetyltransferase or human growth hormone genes directed by promoter sequences from the human alpha 1(I)-collagen gene. Immunostaining for chloramphenicol acetyltransferase demonstrated that collagen promoter activity was restricted to cells involved in the formation of endothelial cords. In comparison to transfected monolayers of BAE cells, the transcriptional activity of the alpha 1(I)-collagen promoter increased by 7-fold in cultures undergoing angiogenesis in vitro. The selective ability of angiogenic endothelium to utilize the alpha 1(I)-collagen promoter is consistent with previous studies showing high levels of alpha 1(I)-collagen mRNA in BAE cells actively engaged in the formation of tubes (Iruela-Arispe, L., Hasselaar, P., and Sage, H. (1991) Lab. Invest. 64, 174-186). We conclude that transcriptional activation of the alpha 1(I)-collagen gene is closely linked to the morphologic alterations in cellular phenotype that accompany the transition of quiescent endothelial monolayers to the angiogenic state.

An internal ribosome binding site can be used to select for homologous recombinants at an immunoglobulin heavy-chain locus

The encephalomyocarditis virus (EMCV) leader sequence is responsible for efficient, cap-independent translation initiation from the viral RNA. It has been used to increase the expression of internal coding regions on polycistronic mRNA encoded by recombinant DNA constructs. We have designed a sequence-replacement-type vector for targeting to immunoglobulin heavy-chain loci in hybridoma cells. Homologous recombination of this vector introduces a human gamma 1 constant-region sequence linked to the EMCV leader and a neomycin phosphotransferase (neo) gene. The resulting cells express a bicistronic mRNA encoding at the 5' end a chimeric murine VDJH-human C gamma 1 heavy chain, followed by neo linked to the internal ribosome binding site provided by the EMCV leader. These homologous recombinants express the chimeric heavy chain at levels equivalent to the heavy chain in the parental hybridoma. This strategy of using an EMCV-neo cassette to obtain efficient selectable marker gene expression has potential application to a range of gene targeting vectors.

Accumulation of ColE1 early replicative intermediates catalyzed by extracts of Escherichia coli dnaG mutant strains

To investigate the events occurring at the replication forks during DNA synthesis, we studied the replication of plasmid ColE1 DNA in vivo and in vitro, using strains of Escherichia coli carrying either the dnaG3(Ts) or dnaG308(Ts) mutation. Extracts of both mutant strains supported in vitro DNA synthesis, but the amount of [3H]TMP incorporated into DNA was always less for mutant extracts than for extracts of revertant strains, which were able to grow at 42 degrees C. Sucrose gradient analysis, Southern blot analysis, and electron microscopy showed that mutant extracts synthesize a large number of early replicative intermediates containing one or two (one on each template strand) fragments at the origin of replication and some completed molecules, either open circles or covalently closed circles. The revertant extracts synthesized more completed molecules although the fraction of templates used was about the same, 0.27 for mutant extracts and 0.21 for revertant extracts. Our results show that a mutation in dnaG causes a block in the synthesis of both leading and lagging strands after initiation, which results in the accumulation of early replicative intermediates. The average size of the newly replicated region in the early replicative intermediates is 730 bases as measured from electron micrographs of early replicative intermediates. We conclude that the DnaG protein functions in lagging strand synthesis and may be necessary for the continuation of leading strand synthesis as well.