Interleukin-7 regulates adipose tissue mass and insulin sensitivity in high-fat diet-fed mice through lymphocyte-dependent and independent mechanisms.

Although interleukin (IL)-7 is mostly known as a key regulator of lymphocyte homeostasis, we recently demonstrated that it also contributes to body weight regulation through a hypothalamic control. Previous studies have shown that IL-7 is produced by the human obese white adipose tissue (WAT) yet its potential role on WAT development and function in obesity remains unknown. Here, we first show that transgenic mice overexpressing IL-7 have reduced adipose tissue mass associated with glucose and insulin resistance. Moreover, in the high-fat diet (HFD)-induced obesity model, a single administration of IL-7 to C57BL/6 mice is sufficient to prevent HFD-induced WAT mass increase and glucose intolerance. This metabolic protective effect is accompanied by a significant decreased inflammation in WAT. In lymphocyte-deficient HFD-fed SCID mice, IL-7 injection still protects from WAT mass gain. However, IL-7-triggered resistance against WAT inflammation and glucose intolerance is lost in SCID mice. These results suggest that IL-7 regulates adipose tissue mass through a lymphocyte-independent mechanism while its protective role on glucose homeostasis would be relayed by immune cells that participate to WAT inflammation. Our observations establish a key role for IL-7 in the complex mechanisms by which immune mediators modulate metabolic functions.

Immune reconstitution following myeloablative allogeneic hematopoietic stem cell transplantation: the impact of expanding CD28negative CD8+ T cells on relapse.

Allogeneic stem cell transplantation has become standard therapy for hematologic malignancies through the positive immunologic graft-versus-leukemia effect. Initial immune recovery relies on peripheral expansion of infused T cells, which switch to a memory-like phenotype. This study prospectively investigated whether changes in subset composition precedes complications after myeloablative HLA-matched transplantation for hematologic malignancies. Of 80 allograft recipients, 18 were still free of clinical complication throughout 395 to 1564 days of follow-up. Compared with this complication-free subgroup, patients who developed chronic graft-versus-host disease (cGVHD) without relapsing recovered similar numbers of circulating T cells with predominance of CD8+ T cells lacking CC-chemokine receptor-7 and CD28 expression throughout the first year after transplantation. Conversely, poor CD8+ T cell recovery with diminished numbers of CD28neg CD8+ T cells (approximately 1/4th of that of relapse-free patients) preceded occurrence of malignant relapse. In multivariate analysis, lower CD28neg CD8+ T cell counts by day 60 postallograft were associated with a greater risk of subsequent relapse (hazard ratio [HR] 0.33; 95% confidence interval [CI]: 0.14-0.76; P = .01). Enumeration of CD28neg CD8+ T cells in patients could assist in predicting risk of relapse and help build an algorithm for accelerating the immune recovery by reducing the immunosuppressive treatment and considering the introduction of preemptive donor lymphocyte infusions.

Nerve growth factor is a potential therapeutic target in breast cancer.

We show here that nerve growth factor (NGF), the prototypic neurotrophin, can be targeted in breast cancer to inhibit tumor cell proliferation, survival, and metastasis. Analysis of a series of biopsies revealed widespread expression of NGF in the majority of human breast tumors, with anti-NGF immunoreactivity concentrated in the epithelial cancer cells. Moreover, immunodeficient mice xenografted with human breast cancer cells and treated with either anti-NGF antibodies or small interfering RNA against NGF displayed inhibited tumor growth and metastasis. Such treatments directed against NGF induced a decrease in cell proliferation with a concomitant increase in apoptosis of breast cancer cells and an inhibition of tumor angiogenesis. Together, these data indicate that targeting NGF in breast cancer may have therapeutic ramifications.

Comparative analysis of naïve and memory CD4+ and CD8+ T-cell subsets in bone marrow and G-CSF-mobilized peripheral blood stem cell allografts: impact of donor characteristics.

OBJECTIVE: Donor T cells expressing lymph node homing receptors are the foremost initiators of acute graft-vs-host disease (aGVHD), and a high proportion of CD4(+)CCR7(+) T cells in human leukocyte antigen-matched allografts has been shown to confer a high risk of aGVHD without interfering in other outcomes. METHODS: Naïve, central memory (T(CM)), effector memory (T(EM)), and terminally differentiated effector memory (T(TD)) subsets, further subdivided by CD28 expression, were compared in 52 bone marrow and 37 granulocyte colony-stimulating factor-mobilized peripheral blood harvests. RESULTS: CCR7(+) cells (naïve and T(CM)) predominated in the CD4(+) population, whereas CD8(+) memory cells were chiefly CCR7(neg) in the grafts. Donor age, antecedent of chronic infections, and graft type were independent factors influencing graft composition. CD8(+) naïve cells negatively correlated and CD8(+) T(EM) positively correlated with age. Cytomegalovirus seropositivity was associated with more CD8(+) T(TD) and diminished CD28 expression. Toxoplasmosis seropositivity was associated with more CD4(+) T(CM) (p = 0.021). Marrow grafts comprised more CD28(+) cells within CD8(+) T(TD), but the percentage of CD4(+)CCR7(+) cells did not differ significantly between the two graft sources. Each of the four CD4(+) subsets and the percentage of CD4(+)CCR7(+) cells (p < 0.001) were correlated between graft and venous blood analyzed in 42 donors before harvest procedures. CONCLUSION: This study provides reference values for CD4(+) and CD8(+) naïve and memory subsets within allografts applicable to the healthy donor population and indicates that beforehand analysis of a whole-blood sample can help evaluating the risk of aGVHD conferred by each donor and, when possible, choosing the one conferring the lowest risk.

Impairment of dendritic cell functionality and steady-state number in obese mice.

There is a finely tuned interplay between immune and neuroendocrine systems. Metabolic disturbances like obesity will have serious consequences on immunity both at the cellular and at the cytokine expression levels. Our in vivo results confirm the immune deficiency of ob/ob mice, leptin deficient and massively obese, characterized by a reduced Ag-specific T cell proliferation after keyhole limpet hemocyanin immunization. In this report, we show that dendritic cells (DCs), major APCs involved in T lymphocyte priming, are affected in obese mice. Both their function and their steady-state number are disturbed. We demonstrate that DCs from ob/ob mice are less potent in stimulation of allogenic T cells in vitro. This impaired functionality is not associated with altered expression of phenotypic markers but with the secretion of immunosuppressive cytokines such as TGF-beta. Moreover, we show increased in vivo steady-state number of epidermal DCs in ob/ob mice, which is not due to a migratory defect. The ob/ob mice are characterized by the absence of functional leptin, a key adipokine linking nutrition, metabolism, and immune functions. Interestingly, intradermal injection of leptin is able to restore epidermal DC number in obese mice. Thus, DCs might be directly sensitive to metabolic disturbances, providing a partial explanation of the immunodeficiency associated with obesity.

Accumulation of memory T cells from childhood to old age: central and effector memory cells in CD4(+) versus effector memory and terminally differentiated memory cells in CD8(+) compartment.

Memory T cells can be classified as central memory (T(CM), CD45RA(neg)CCR7(+)), effector memory (T(EM), CD45RA(neg)CCR7(neg)), and terminally differentiated cells (T(TD), CD45RA(+)CCR7(neg)) with different homing and effector capacities. In 101 healthy subjects aged from 5 to 96 years, distinct dynamics were evidenced between circulating CD4(+) and CD8(+) T cell populations. Naive CD4(+) and CD8(+) T cells decreased linearly with age, CD8(+) twice more rapidly. Memory cells outnumbered naive cells on average at 37.4 in the CD4(+) and 29.5 years of age in the CD8(+) pool. CD4(+) T(CM) and T(EM) cells were positively correlated and increased linearly at a similar rate with age, while CD4(+) T(TD) remained rare. CD8(+) T(EM) and T(TD) accumulated linearly with age, while T(CM) increased only slightly, and each memory subset was negatively correlated to the two others. Almost all CD8(+) T(TD) and some CD8(+) T(EM) had lost CD28 expression. Despite different dynamics, each individual CD4(+) naive and memory subset was correlated to the synonymous CD8(+) subset. Half of the subjects aged 65 years or older were characterized by extremely reduced CD8(+) naive and increased CD8(+) T(TD) cell counts, which could indicate an acceleration of the decay of the immune system from this age onward.

Host glucose metabolism mediates T4 and IL-7 action on Schistosoma mansoni development.

Interleukin (IL-)7 and thyroxin (T4) favor Schistosoma mansoni development. Their effect is similar, rather than identical; moreover, cotreatment acts synergistically on parasites. This questioned a common mediator to their action, which we hypothesized was host glucose metabolism. Infection with S. mansoni resulted in an early peak in glycemia immediately followed by a peak of insulinemia (D7-21). In IL-7 + T4 cotreated infected animals, the peak of insulin was abrogated. We further assessed the consequences of experimentally induced glucose- or insulin-level variations on parasite development. Insulin treatment from day 14 to day 21 post-infection (PI) led to increased worm burden and parasite size, thus mimicking the effect of T4 on schistosome development. Interestingly, insulin treatment did not modify glycemia yet abrogated the hyperinsulinemia, normally occurring during infection. Finally, these treatments were associated with an alteration of the expression of parasite genes involved in glucose uptake. These experiments characterize the elaborate links between parasite and host metabolism and their reciprocal influences.

Early variations of host thyroxine and interleukin-7 favor Schistosoma mansoni development.

Schistosoma mansoni induces, in the vertebrate host, cutaneous production of interleukin-7 (IL-7), which is beneficial for parasite establishment and development. Infection of mice deficient in IL-7 expression leads to parasite dwarfism. Because similar findings were previously described in hypothyroid mice, this study aimed to elucidate the potential link between IL-7 and thyroid hormones (THs), using several models including hypo- and hyperthyroid mice, modified either transiently or constitutively. Mice treated with thyroxine led to increased worm numbers and development of giant worms, whereas an iodine-deficient diet reduced parasite maturation, egg laying, and liver pathology. Conversely, mice genetically deficient for either of the nuclear TH receptors displayed normal worm development despite modifications in hormone levels, suggesting that thyroxine action is mediated through host receptors. In addition, no modification of antibody titers has been evidenced in thyroxine-treated mice, whereas antibody levels were altered in transgenic animals. These observations suggest that the immune system is not likely to be involved in the modifications of parasite development reported in this study. Interestingly, concomitant treatment with IL-7 and thyroxine had a synergistic effect, leading to recovery of very large worms, thus raising questions about the complexity of interactions between IL-7 and metabolic hormones.