Mammalian circadian behavior is governed by a central clock in the suprachiasmatic nucleus of the brain hypothalamus, and its intrinsic period length is believed to affect the phase of daily activities. Measurement of this period length, normally accomplished by prolonged subject observation, is difficult and costly in humans. Because a circadian clock similar to that of the suprachiasmatic nucleus is present in most cell types, we were able to engineer a lentiviral circadian reporter that permits characterization of circadian rhythms in single skin biopsies. Using it, we have determined the period lengths of 19 human individuals. The average value from all subjects, 24.5 h, closely matches average values for human circadian physiology obtained in studies in which circadian period was assessed in the absence of the confounding effects of light input and sleep–wake cycle feedback. Nevertheless, the distribution of period lengths measured from biopsies from different individuals was wider than those reported for circadian physiology. A similar trend was observed when comparing wheel-running behavior with fibroblast period length in mouse strains containing circadian gene disruptions. In mice, inter-individual differences in fibroblast period length correlated with the period of running-wheel activity; in humans, fibroblasts from different individuals showed widely variant circadian periods. Given its robustness, the presented procedure should permit quantitative trait mapping of human period length.

86:1204-1210). Like IL-4, IL-10 is secreted by Th2 lymphocytes and is inhibitory to several macrophage functions. In the present study, IL-10 was tested and compared to IL-2, IL-4, IL-6, and IFNy for its capacity to modulate synthesis of 92-kD gelatinase, interstitial collagenase and TIMP in human macrophages and monocytes. We found that IL-10, just like IL-4, inhibited the production of 92-kD gelatinase and blocked LPS-, as well as killed Staphylococcus aureus-induced, interstitial collagenase production. The principal finding of this study, however, was that IL-10, in distinction to IL-4, produced a dose-dependent stimulation in the biosynthesis of TIMP-1. TIMP-2 production was not affected. IL-10 regulated the expression of 92-kD gelatinase and TIMP-1 at the pretranslational level. Furthermore, IL-10 regulation was cell typespecific, as it had no effect on the production of metalloproteinases or TIMP by human fibroblasts. In summary, IL-10 has a potent and unique effect upon tissue macrophages and blood monocytes by enhancing TIMP-1 production while decreasing metalloproteinase biosynthesis. (J. Clin. Invest. 1995. 96:2304-2310

The secreted form of the interleukin-1 receptor antagonist (IL-1Ra) is an acute-phase protein intervening in the counterregulation of inflammatory processes. We previously showed that this cytokine antagonist is upregulated in the serum of obese patients, correlating with BMI and insulin resistance. In this study, we examined the expression pattern of IL-1Ra and showed that it is highly expressed not only in liver and spleen, but also in white adipose tissue (WAT), where it is upregulated in obesity. In WAT of obese humans, IL-1Ra was also markedly increased. Moreover, human WAT explants secreted IL-1Ra into the medium, a process that could be stimulated fivefold by interferon-␤. Finally, lipopolysaccharide administration induced a longlasting expression of IL-1Ra in mouse WAT, suggesting that adipose tissue is an important source of IL-1Ra in both obesity and inflammation. In summary, we demonstrated that WAT is one of the most important sources of IL-1Ra quantitatively, suggesting that this tissue could represent a novel target for anti-inflammatory treatment. Moreover, it can be speculated that IL-1Ra, whose production is markedly increased in WAT in obese individuals, contributes further to weight gain because of its endocrine and paracrine effects on the hypothalamus and adipocytes, respectively. Diabetes

IntroductionT helper (Th) cells may differentiate into distinct functional subsets according to the circumstances in which naive precursors encounter the nominal antigen for which they are specific. In the presence of interleukin-12 (IL-12), Th precursor cells become Th1 and high producers of interferon-␥ (IFN-␥), whereas in the presence of IL-4 they become Th2 and high producers of IL-4 and IL-5. These subsets have fundamentally different effector functions, in particular for their capacity to induce monocytes activation. 1 Recently, a distinct Th subset has been characterized in mice 2-6 and humans [7][8][9][10][11] for its high production of IL-17, the use of retinoid-related orphan receptor ␥t (ROR␥t) as master transcription factor, 12 its role in protection against extracellular bacteria and fungi, and in the pathogenesis of several autoimmune conditions, such as collageninduced arthritis, experimental autoimmune encephalomyelitis, and an animal model of inflammatory bowel disease. 4,13,14 Of interest, the generation of Th17 from naive precursors may follow different requirements in mice and humans. In mice, commitment to the Th17 lineage is dependent on transforming growth factor-␤ (TGF-␤), IL-1␤, and IL-6, whereas in humans IL-1␤ and IL-6 but not TGF-␤ appear to be required. 10,[15][16][17][18] The role of IL-23 in Th17 differentiation and effector function is still debated. IL-23 is a member of the IL-6 family of cytokines that shares with IL-12 the p40 subunit and has a unique p19 subunit. 19 IL-23 promotes Th17 responses in vivo but may be more important for the survival and population expansion of Th17 cells than for Th17 lineage commitment. 3,5,16 However, in conjunction with IL-1, IL-23 is sufficient for inducing naive human T cells to produce IL-17A, IL-17F, IL-22, IL-26, IFN-␥, C-C chemokine ligand 20 (CCL20)/ macrophage inflammatory protein 3␣ (MIP-3␣), and the transcription factor ROR␥t. 10 Moreover, mice lacking IL-23 are fully resistant to experimental autoimmune encephalomyelitis, collageninduced arthritis, and inflammatory bowel disease.The pattern of chemokine receptors expressed varies according to the differentiation stage and effector function of T cells. 20 The preferential expression of C-C chemokine receptor 6 (CCR6) distinguishes human Th17 from other Th subsets. 7,8,21,22 It should be stressed, however, that expression of CXC chemokine receptor 3 (CXCR3) within CCR6 ϩ T cells identifies T cells with preferential IFN-␥ production in response to purified protein derivative, whereas IL-17 production in response to Candida albicans hyphae is restricted to CCR6 ϩ CCR4 ϩ cells. 7 IL-17, when overexpressed in murine knee joint, causes inflammation and bone erosion. 23 Likewise, erosion observed in streptococcal cell wall-induced arthritis is highly reduced in IL-17R Ϫ/Ϫ and is associated with impaired expression of matrix metalloproteinases (MMPs). 24 T-cell clones producing IL-17 were generated from the synovium and synovial fluid of rheumatoid arthritis patients, 25 and IL-17 was shown t...

Ligands of the aryl hydrocarbon receptor (AHR), a transcription factor mediating the effects of dioxin, favor Th17 differentiation and exacerbate autoimmunity in mice. We investigated how AHR ligands affected human T-cell polarization. We found that the high affinity and stable AHR-ligand dioxin as well as the natural AHR-ligand 6-formylinolo [3,2-b] carbazole induced the downstream AHR-target cytochrome P450A1, and without affecting IFN-c, they enhanced IL-22 while simultaneously decreasing IL-17A production by CD4 1 T cells. The specific AHRinhibitor CH-223191 abolished these effects. Furthermore, blockade of IL-23 and IL-1, important for Th17 expansion, profoundly decreased IL-17A but not IL-22 production. AHR agonists reduced the expression of the Th17 master transcription factor retinoic acid-related orphan receptor C (RORC), without affecting T-bet, GATA-3 and Foxp3. They also decreased the expression of the IL-23 receptor. Importantly, AHR-ligation did not only decrease the number of Th17 cells but also primed naïve CD4 1 T cells to produce IL-22 without IL-17 and IFN-c. Furthermore, IL-22 single producers did not express CD161, which distinguished them from the CD161 1 Th17 cells. Hence, our data provide compelling evidence that AHR activation participates in shaping human CD4 1 T-cell polarization favoring the emergence of a distinct subset of IL-22-producing cells that are independent from the Th17 lineage. IntroductionLocal cytokine milieu during antigen presentation profoundly affects the differentiation program of CD4 1 T cells [1]. In the mouse, TGF-b, in the presence of IL-6 and pro-inflammatory cytokines, favors the emergence of Th17 cells that produce IL-17 and express the master transcription factor retinoic acid-related orphan receptor (ROR)gt [2][3][4][5][6]. Th17 cells are expanded and terminally differentiated in the presence of . Human Th17 cells may be generated in the presence of IL-1 and IL-23; IL-1 and IL-6; or . Th17 cells express CCR6 and 2450produce the CCR6-ligand CCL20, thereby amplifying Th17 cell recruitment at sites of inflammation [11]. IL-22, a member of the IL-10-family, is produced by Th17 cells, and to some extent by Th1 cells, NKT cells, NK cells and lymphoid tissue inducer-like cells [12]. IL-22 signals via a receptor consisting of IL-22R and IL-10R2 subunits [11]. Cells of hemapoietic origin do not express IL-22R; instead, IL-2R is highly expressed by epithelial cells of the gastrointestinal tract and the skin. In the mouse, IL-23 was shown to drive preferential expansion of cells that co-express IL-22 and IL-17, that may synergize to augment the expression of genes involved in defense against microbial pathogens [13,14]. However, several mouse models of infection and autoimmunity suggested distinct roles for .In addition to cytokines, other mediators may impact CD4 1 T-cell differentiation. We and others have shown that prostaglandin E2 (PGE2) favors human Th17 expansion [20][21][22]. Furthermore, ligands of the aryl hydrocarbon receptor (AHR) exert a role. AHR is a...