IL-7-mediated protection of pro and pre-B cells from the adverse effects of corticosterone

Enterocolitis causes profound lymphoid depletion in endothelin receptor B- and endothelin 3-null mouse models of Hirschsprung-associated enterocolitis

Potentially life-threatening enterocolitis is the most frequent complication in children with colonic aganglionosis (Hirschsprung disease, HSCR), and little is known about the mechanisms leading to enterocolitis. Splenic lymphopenia has been reported in the Endothelin Receptor B (Ednrb)-null mouse model of HSCR that develops enterocolitis. In this study, we sought to identify molecular mechanisms underlying this immune phenotype. We employed the Ednrb(-/-) mouse, and the knockout of its ligand, Edn3 (Edn3(-/-)). The major finding is that enterocolitis in the Ednrb(-/-) and Edn3(-/-) mice lead to thymic involution, splenic lymphopenia, and suppression of B lymphopoiesis as a consequence of colonic aganglionosis, not an intrinsic Edn3-Ednrb signaling defect directly affecting the lymphoid organs. We showed that adoptive transfer of Ednrb(-/-) marrow repopulated the RAG2-null mice marrow, thymus and spleen without development of enterocolitis. We identified the glucocorticoid corticosterone, as a potential mediator of the immune phenotype. This previously unrecognized pattern of immune abnormalities in mouse is nearly identical to lymphoid depletion in neonatal sepsis during severe physiological stress, suggesting that the mouse model used here could be also used for sepsis studies.

Novel molecular and cellular therapeutic targets in acute lymphoblastic leukemia and lymphoproliferative disease

While the outcome for pediatric patients with lymphoproliferative disorders (LPD) or lymphoid malignancies, such as acute lymphoblastic leukemia (ALL), has improved dramatically, patients often suffer from therapeutic sequelae. Additionally, despite intensified treatment, the prognosis remains dismal for patients with refractory or relapsed disease. Thus, novel biologically targeted treatment approaches are needed. These targets can be identified by understanding how a loss of lymphocyte homeostasis can result in LPD or ALL. Herein, we review potential molecular and cellular therapeutic strategies that (i) target key signaling networks (e.g., PI3K/AKT/mTOR, JAK/STAT, Notch1, and SRC kinase family-containing pathways) which regulate lymphocyte growth, survival, and function; (ii) block the interaction of ALL cells with stromal cells or lymphoid growth factors secreted by the bone marrow microenvironment; or (iii) stimulate innate and adaptive immune responses.

Acinar cell apoptosis in Serpini2-deficient mice models pancreatic insufficiency

Pancreatic insufficiency (PI) when left untreated results in a state of malnutrition due to an inability to absorb nutrients. Frequently, PI is diagnosed as part of a larger clinical presentation in cystic fibrosis or Shwachman-Diamond syndrome. In this study, a mouse model for isolated exocrine PI was identified in a mouse line generated by a transgene insertion. The trait is inherited in an autosomal recessive pattern, and homozygous animals are growth retarded, have abnormal immunity, and have reduced life span. Mice with the disease locus, named pequeño (pq), exhibit progressive apoptosis of pancreatic acinar cells with severe exocrine acinar cell loss by 8 wk of age, while the islets and ductal tissue persist. The mutation in pq/pq mice results from a random transgene insertion. Molecular characterization of the transgene insertion site by fluorescent in situ hybridization and genomic deletion mapping identified an approximately 210-kb deletion on Chromosome 3, deleting two genes. One of these genes, Serpini2, encodes a protein that is a member of the serpin family of protease inhibitors. Reintroduction of only the Serpini2 gene by bacterial artificial chromosome transgenic complementation corrected the acinar cell defect as well as body weight and immune phenotypes, showing that deletion of Serpini2 causes the pequeño phenotype. Dietary supplementation of pancreatic enzymes also corrected body size, body weight, and immunodeficiency, and increased the life span of Serpini2-deficient mice, despite continued acinar cell loss. To our knowledge, this study describes the first characterized genetic animal model for isolated PI. Genetic complementation of the transgene insertion mutant demonstrates that Serpini2 deficiency directly results in the acinar cell apoptosis, malabsorption, and malnutrition observed in pq/pq mice. The rescue of growth retardation, immunodeficiency, and mortality by either Serpini2 bacterial artificial chromosome transgenic expression or by pancreatic enzyme supplementation demonstrates that these phenotypes are secondary to malnutrition in pq/pq mice.

Production of human B cells from CD34+CD38- T- B- progenitors in organ culture by sequential cytokine stimulation

We investigated sequential cytokine addition on human hematopoietic stem cell (HSC) differentiation in murine fetal liver (FL), fetal spleen (FS) and bone marrow (BM) organ cultures (OC). Tissues were colonized with unpurified or FACS sorted CD34+CD38-CD10-CD19-CD3-CD8-CD4-(T- B-) cells from human cord blood (HUCB). CD19+ cell production and kinetics differed in each tissue. Fetal liver organ cultures (FLOC) inoculated with CD34+CD38-T-B- cells produced fewer CD19+ cells than fetal liver organ culture (FLOC) cultured with unpurified HUCB. CD19+ cell production was restored in the CD34+CD38-T-B- organ cultures by treating with SCF, LIF and IL-6 followed by IL-7 and removing all cytokines for the last 3 days of culture (a six-fold increase). FLOC also produced CD34+CD38-T-B- cells and monocyte-lineage CD33+CD14- cells, both of which increased after cytokine treatment. Re-colonization of secondary FLOC with CD34+CD38-T-B- cells generated in primary FLOC produced additional B-cells, monocytes and CD34+CD38- cells suggesting that the primary cells retained HSC activity. Expansion and differentiation of HSCs depended on the microenvironment of the recipient tissue as well as addition of cytokines in the appropriate order.

Peroxisome proliferator-activated receptor alpha regulates B lymphocyte development via an indirect pathway in mice

Peroxisome proliferator-activator receptor alpha (PPARalpha), a member of the nuclear receptor superfamily, has been implicated in the regulation of inflammation and immune response. Adaptive immune responses are suppressed by exposure to PPARalpha agonists, resulting in severe thymus and spleen atrophy. In addition, the decline in both T and B cells is due in part to the loss of splenocytes upon exposure to PPARalpha agonists. Thus, the current study was designed to examine the effect of Wy-14,643, a potent PPARalpha agonist, on B cell development in bone marrow from wild-type and PPARalpha-null mice. Significantly decrease in pro/pre-B cell and total B220(+) cell was observed in wild-type mice in bone marrow upon Wy-14,643 treatment, but not in PPARalpha-null mice. Immature and mature B cell populations are not affected. This suggests that PPARalpha is involved in the development of B cell during lymphoid lineage. However, surprisingly, PPARalpha mRNA was absent in bone marrow as revealed by RT-PCR. Therefore, the effect of PPARalpha on B cell development is by an indirect mechanism.

Reprogramming of the immune system during zinc deficiency

Thymic atrophy, lymphopenia, and compromised cell- and antibody-mediated responses that cause increased rates of infections of longer duration are the immunological hallmarks of zinc deficiency (ZD) in humans and higher animals. As the deficiency advances, a reprogramming of the immune system occurs, beginning with the activation of the stress axis and chronic production of glucocorticoids that accelerate apoptosis among pre-B and -T cells. This reduces lymphopoiesis and causes atrophy of the thymus. In contrast, myelopoiesis is preserved, thereby providing protection for the first line of immune defense or innate immunity. Changes in gene expression for cytokines, DNA repair enzymes, zinc transporters, signaling molecules, etc., suggest that cells of the immune system are attempting to adapt to the stress of suboptimal zinc. Better understanding of the molecular and cellular changes made in response to inadequate zinc should lead to the development of immunotherapeutic interventions.

Transforming growth factor beta enhances the glucocorticoid response of the mouse mammary tumor virus promoter through Smad and GA-binding proteins

Tissue-specific transcription is advantageously investigated by using viral promoters, which are selected for compact regulatory elements. Mouse mammary tumor virus (MMTV) has adapted to specialized cell types and targets initially B lymphocytes. We previously showed that, in B-cell lines, glucocorticoid-induced MMTV transcription requires an ETS family factor, GA-binding protein (GABP), bound in tandem to the MMTV DNA next to the glucocorticoid receptor (GR). We now report that transforming growth factor beta (TGF-beta) superinduces this response up to 10-fold through binding of its effectors, Smads, between the GABP-binding motifs. The basal level was unaffected. The TGF-beta-glucocorticoid cooperation also depended on GR and GABP binding, was transferable to another promoter, and occurred both with transiently transfected and with integrated templates. Smad3 associated in vitro with GR, with GABPalpha (via the MH2 domain), and with GABPbeta, Smad4 only with GABPalpha. Interactions of Smad3 with GABP (when coexpressed or endogenous to B cells) were shown by coprecipitation and by mammalian two-hybrid assay. This composite DNA element integrates three signaling pathways deriving from TGF-beta, glucocorticoid hormones, and a unique ETS factor, and may allow MMTV to exploit factors from the milk. It may as well indicate novel possibilities for cellular regulatory networks.