Salivary uric acid across child development and associations with weight, height, and body mass index.

Introduction: Obesity during childhood is a serious and growing chronic disease with consequences for lifelong health. In an effort to advance research into the preclinical indicators of pediatric obesity, we examined longitudinal assessments of uric acid concentrations in saliva among a cohort of healthy children from age 6-months to 12-years (n's per assessment range from 294 to 727). Methods: Using data from a subsample of participants from the Family Life Project (an Environmental influences on Child Health Outcomes Program cohort), we: (1) characterized salivary uric acid (sUA) concentrations from infancy to early adolescence by sex and race; (2) assessed changes in sUA levels across development; and (3) evaluated associations between sUA concentrations and measures of child weight, height, and body mass index (BMI). Across four assessments conducted at 6-, 24-, 90-, and 154-months of age, 2,000 saliva samples were assayed for UA from 781 participants (217 participants had sUA data at all assessments). Results: There were no significant differences in sUA concentrations by sex at any assessment, and differences in sUA concentrations between White and non-White children varied by age. At the 90- and 154-month assessments, sUA concentrations were positively correlated with measures of child weight, height, and BMI (90-month: weight- ρ(610) = 0.13, p < 0.01; height- ρ(607) = 0.10, p < 0.05; BMI- ρ(604) = 0.13, p < 0.01; 154-month: weight- ρ(723) = 0.18, p < 0.0001; height- ρ(721) = 0.10, p < 0.01; BMI- ρ(721) = 0.17, p < 0.0001). Group based trajectory modeling identified two groups of children in our sample with distinct patterns of sUA developmental change. The majority (72%) of participants showed no significant changes in sUA across time ("Stable" group), while 28% showed increases in sUA across childhood with steep increases from the 90- to 154-month assessments ("Increasing" group). Children in the Increasing group exhibited higher sUA concentrations at all assessments (6-month: t(215) = -5.71, p < 0.001; 24-month: t(215) = -2.89, p < 0.01; 90-month: t(215) = -3.89, p < 0.001; 154-month: t(215) = -19.28, p < 0.001) and higher weight at the 24- and 90-month assessments (24-month: t(214) = -2.37, p < 0.05; 90-month: t(214) = -2.73, p < 0.01). Discussion: Our findings support the potential utility of sUA as a novel, minimally-invasive biomarker that may help advance understanding of the mechanisms underlying obesity as well as further surveillance and monitoring efforts for pediatric obesity on a large-scale.

Mechanism of self-tolerance of gamma/delta T cells in epithelial tissue.

The present study examined mechanisms of tolerance for T cell receptor gamma/delta (TCR-gamma/delta) cells. Using a transgenic (Tg) model, we demonstrate that although alloantigen (Ag)-specific TCR-gamma/delta cells are deleted in the thymus and spleen of Ag-bearing mice, intraepithelial lymphocytes (IELs) expressing normal levels of the Tg TCR were present. However, Tg+ IELs from Ag-bearing mice were unresponsive to activation. Furthermore, self-reactive Tg+ IELs decreased in number over time. Thus, in epithelial tissue, Tg TCR-gamma/delta cells are eliminated subsequent to and most likely as a result of the induction of clonal anergy.

Control of inflammation, cytokine expression, and germinal center formation by BCL-6.

The gene encoding the BCL-6 transcriptional repressor is frequently translocated and mutated in diffuse large cell lymphoma. Mice with a disrupted BCL-6 gene developed myocarditis and pulmonary vasculitis, had no germinal centers, and had increased expression of T helper cell type 2 cytokines. The BCL-6 DNA recognition motif resembled sites bound by the STAT (signal transducers and activators of transcription) transcription factors, which mediate cytokine signaling. BCL-6 could repress interleukin-4 (IL-4)-induced transcription when bound to a site recognized by the IL-4-responsive transcription factor Stat6. Thus, dysregulation of STAT-responsive genes may underlie the inflammatory disease in BCL-6-deficient mice and participate in lymphoid malignancies.

Control of self-reactivity in the intestine.

In the intestine maintenance of self-tolerance may involve tissue-specific self-Ags, APCs, 'second signals', and extrathymic pathways of T cell maturation. These factors combine to create a unique environment where autoimmune tissue destruction is prevented despite local inflammatory influences. In this review we summarize our findings using a TCR-gamma delta transgenic model where self-tolerance was maintained by clonal deletion for cells localizing to peripheral lymphoid tissue and by clonal anergy for cells localizing to the intraepithelial compartments. Several possible explanations exist for these results but in general, these findings have implications for the maintenance of self-tolerance of normal TCR-alpha beta and TCR-gamma delta IELs in epithelial tissues such as the intestine.

Regulation of lymphocyte cell fate decisions and lymphomagenesis by BCL-6.

Genetic alterations of the BCL-6 gene in mice and man have established BCL-6 as a pivotal regulator of normal differentiation of B and T lymphocytes as well as one of the most frequently translocated oncogenes in human B cell lymphomas. As an oncogene, BCL-6 has not been easy to place into existing paradigms of cellular transformation. Rather, it is likely that the function of BCL-6 as a regulator of lymphocyte differentiation is subverted in BCL-6-induced lymphomas. The lymphomas in which BCL-6 is translocated are all suspected to arise from the germinal center B lymphocyte. Given the selective expression of BCL-6 protein in normal germinal center B lymphocytes and the requirement for BCL-6 in germinal center development, the functions of BCL-6 in normal and malignant B cells are probably intertwined. The BCL-6 protein is a potent transcriptional repressor which presumably controls lymphocyte differentiation and induces lymphomas by regulating the expression of key downstream target genes.

Characterization of an alternative exon of the murine T cell receptor beta-chain. Pattern of expression and evolutionary conservation.

In this report, we characterize an alternate gene element of the murine TCR beta-chain. First, we have looked at the expression of the alternate exon, C beta 0, in normal T cell clones, as well as in fetal vs adult whole thymus. The C beta 0 exon is expressed in only 1% or less of TCR-beta messages in four of four mature T cell clones examined. C beta 0 is found at 10-fold higher levels in both fetal and adult thymus mRNA. Thus C beta 0 is developmentally regulated by T cells, although expression of the alternate exon is relatively constant from the fetal thymus to the adult thymus. Second, evolutionary conservation of the C beta 0 gene element was studied in both the rat and the human. The rat beta-locus contains a gene element highly homologous to the mouse C beta 0 gene, but the rat C beta 0 gene contains mutations in both splice sites that probably prevent the gene element from being spliced into mRNA. We have also sequenced the first exon of rat C beta 1, and find that the C beta 0 exon and the intron around C beta 0 are conserved between rat and mouse to the same level as the C beta 1 coding region. The intron around C beta 1, in contrast, shows the decrease in conservation between the two species that is expected for a noncoding region. Analysis of the putative C beta 0-containing region in the human reveals no sequences homologous to the C beta 0 gene element. Because the mouse is the only species that has conserved a functional C beta 0 gene, we conclude that the C beta 0 exon does not play a general role in T cell development.

BCL-6-deficient mice reveal an IL-4-independent, STAT6-dependent pathway that controls susceptibility to infection by Leishmania major.

The BCL-6 gene negatively regulates Th2 responses as shown by the finding that BCL-6-deficient (BCL-6-/-) mice develop a lethal Th2-type inflammatory disease. The response of inbred mouse strains to infection with Leishmania major is under genetic control; BALB/c mice are susceptible and develop a progressive parasite burden, whereas most other common laboratory strains of mice are resistant to infection. We found that BCL-6-/- mice on a resistant genetic background (C57BL/6 x 129 intercrossed mice) were highly susceptible to L. major infection; they resembled BALB/c mice in terms of lesion size, parasite load, and the production of Th2 cytokines. BCL-6-/-IL-4-/- double-mutant mice were also susceptible to L. major infection and produced 10-fold higher levels of the Th2 cytokine IL-13 than IL-4-/- littermate controls. By contrast, BCL-6-/-STAT6-/- double-mutant mice were resistant to L. major infection despite also producing elevated levels of IL-13. These results show that STAT6 is required for susceptibility to L. major infection and suggest that IL-13 signaling through STAT6 may contribute to a nonhealing, exacerbated L. major infection.

Evidence for programmed cell death of self-reactive gamma delta T cell receptor-positive thymocytes.

The negative selection of T cells expressing the gamma delta T cell antigen receptor (gamma delta T cells) was studied using transgenic mice expressing a gamma delta receptor with specificity for an H-2T-linked class I major histocompatibility complex molecule from H-2b mice. The potentially self-reactive gamma delta thymocytes in H-2b/d transgenic mice are larger and have lower levels of gamma delta T cell receptor expression than gamma delta thymocytes from H-2d mice. H-2b/d gamma delta thymocytes do not respond to H-2b antigen-presenting cells, and thus are inactive compared to H-2d gamma delta thymocytes. However, the H-2b/d gamma delta thymocyte population, but not the H-2d gamma delta thymocyte population, undergoes a high rate of programmed cell death when placed in overnight culture. These observations constitute the first direct evidence that self-reactive gamma delta thymocytes undergo programmed cell death. This in vitro programmed cell death of self-reactive gamma delta thymocytes may reflect the clonal deletion process that results in a depletion of gamma delta T cells in the peripheral lymphoid organs of adult H-2b/d mice. We also present evidence that self-reactive gamma delta T cells, similarly to alpha beta T cells, undergo a lesser degree of clonal deletion in neonatal mice compared to adult mice.

T helper type 2 inflammatory disease in the absence of interleukin 4 and transcription factor STAT6.

An important signaling pathway for the differentiation of T helper type 2 (TH2) cells from uncommitted CD4 T cell precursors is activation of the STAT6 transcription factor by interleukin 4 (IL-4). The protooncogene BCL-6 is also involved in TH2 differentiation, as BCL-6 -/- mice develop an inflammation of the heart and lungs associated with an overproduction of TH2 cells. Surprisingly, IL-4 -/- BCL-6 -/- and STAT6 -/- BCL-6 -/- double-mutant mice developed the same TH2-type inflammation of the heart and lungs as is characteristic of BCL-6 -/- mice. Furthermore, a TH2 cytokine response developed in STAT6 -/- BCL-6 -/- and IL-4 -/- BCL-6 -/- mice after immunization with a conventional antigen in adjuvant. In contrast to these in vivo findings, STAT6 was required for the in vitro differentiation of BCL-6 -/- T cells into TH2 cells. BCL-6, a transcriptional repressor that can bind to the same DNA binding motifs as STAT transcription factors, seems to regulate TH2 responses in vivo by a pathway independent of IL-4 and STAT6.

Self-reactive gamma delta T cells are eliminated in the thymus.

The genes encoding a gamma delta T-cell receptor specific for a major histocompatibility complex class I molecule encoded by the TIa locus have been inserted into the mouse germ line. In mice that do not express the TIa-encoded determinant, transgenic gamma delta T cells are a functional component of the CD4-CD8- 'double-negative' T cells in the thymus and peripheral lymphoid organs. In mice that express the TIa-encoded determinant, there are no transgenic gamma delta T cells in peripheral lymphoid organs, and there are no thymocytes expressing normal levels of the transgenic gamma delta T-cell receptor.

LYSP100-associated nuclear domains (LANDs): description of a new class of subnuclear structures and their relationship to PML nuclear bodies.

The PML gene is fused to the retinoic acid receptor alpha (RAR alpha) gene in t(15;17) acute promyelocytic leukemia (APL), creating a PML-RAR alpha fusion oncoprotein. The PML gene product has been localized to subnuclear dot-like structures variously termed PODs, ND10s, Kr bodies, or PML nuclear bodies (PML NBs). The present study describes the cloning of a lymphoid-restricted gene, LYSP100, that is homologous to another protein that localizes to PML NBs, SP100. In addition to SP100 homology regions, one LYSP100 cDNA isoform contains a bromodomain and a PHD/TTC domain, which are present in a variety of transcriptional regulatory proteins. By immunofluorescence, LYSP100 was localized to nuclear dots that were surprisingly largely nonoverlapping with PML NBs. However, a minority of LYSP100 nuclear dots exactly colocalized with PML and SP100. We term the LYSP100 structures "LANDs," for LYSP100-associated nuclear domains. Although LYSP100 is expressed only in lymphoid cells, LANDs could be visualized in HeLa cells by transfection of a LYSP100 cDNA. Immunoelectron microscopy revealed LANDs to be globular, electron-dense structures morphologically distinct from the annular structures characteristic of PML NBs. LANDs were most often found in the nucleoplasm, but were also found at the nuclear membrane and in the cytoplasm, suggesting that these structures may traffic between the cytoplasm and the nucleus. By double-immunogold labeling of PML and LYSP100, some LANDs were shown to contain both PML and LYSP100. Thus, PML is localized to a second subnuclear domain that is morphologically and biochemically distinct from PML NBs.

Using GIS to study the health impact of air emissions.

Geographical Information Systems (GIS) is a fast-developing technology with an ever-increasing number of applications. Air dispersion modeling is a well-established discipline that can produce results in a spatial context. The marriage of these two applications is optimal because it leverages the predictive capacity of modeling with the data management, analysis, and display capabilities of GIS. In the public health arena, exposure estimation techniques are invaluable. The utilization of air emission data, such as U.S. EPA Toxic Release Inventory (TRI) data, and air dispersion modeling with GIS enable public health professionals to identify and define the potentially exposed population, estimate the health risk burden of that population, and determine correlations between point-based health outcome results with estimated health risk.

BCL-6 regulates chemokine gene transcription in macrophages.

The transcriptional repressor protein BCL-6, implicated in the pathogenesis of B cell lymphoma, regulates lymphocyte differentiation and inflammation. We investigated the mechanism for the T helper cell subset 2 (TH2)-type inflammation that occurs in BCL-6-/- mice. Using chimeric mice we found that the TH2-type inflammation is dependent upon nonlymphoid cells. We identified three chemokines, MCP-1, MCP-3 and MRP-1, which are negatively regulated by BCL-6 in macrophages. Promoter analysis revealed that BCL-6 is a potent repressor of MCP-1 transcription. Our results provide a mechanism for the regulation of TH2-type inflammation by BCL-6 and link TH2 differentiation to innate immunity.