Interleukin-7 mediates the homeostasis of naïve and memory CD8 T cells in vivo

The naïve and memory T lymphocyte pools are maintained through poorly understood homeostatic mechanisms that may include signaling via cytokine receptors. We show that interleukin-7 (IL-7) plays multiple roles in regulating homeostasis of CD8+ T cells. We found that IL-7 was required for homeostatic expansion of naïve CD8+ and CD4+ T cells in lymphopenic hosts and for CD8+ T cell survival in normal hosts. In contrast, IL-7 was not necessary for growth of CD8+ T cells in response to a virus infection but was critical for generating T cell memory. Up-regulation of Bcl-2 in the absence of IL-7 signaling was impaired after activation in vivo. Homeostatic proliferation of memory cells was also partially dependent on IL-7. These results point to IL-7 as a pivotal cytokine in T cell homeostasis.

Lymphopenia in interleukin (IL)-7 gene-deleted mice identifies IL-7 as a nonredundant cytokine

Interleukin (IL)-7 is a potent stimulus for immature T and B cells and, to a lesser extent, mature T cells. We have inactivated the IL-7 gene in the mouse germline by using gene-targeting techniques to further understand the biology of IL-7. Mutant mice were highly lymphopenic in the peripheral blood and lymphoid organs. Bone marrow B lymphopoiesis was blocked at the transition from pro-B to pre-B cells. Thymic cellularity was reduced 20-fold, but retained normal distribution of CD4 and CD8. Splenic T cellularity was reduced 10-fold. Splenic B cells, also reduced in number, showed an abnormal population of immature B cells in adult animals. The remaining splenic populations of lymphocytes showed normal responsiveness to mitogenic stimuli. These data show that proper T and B cell development is dependent on IL-7. The IL-7-deficient mice are the first example of single cytokine-deficient mice that exhibit severe lymphoid abnormalities.

IL-7 is critical for homeostatic proliferation and survival of naive T cells

In T cell-deficient conditions, naive T cells undergo spontaneous "homeostatic" proliferation in response to contact with self-MHC/peptide ligands. With the aid of an in vitro system, we show here that homeostatic proliferation is also cytokine-dependent. The cytokines IL-4, IL-7, and IL-15 enhanced homeostatic proliferation of naive T cells in vitro. Of these cytokines, only IL-7 was found to be critical; thus, naive T cells underwent homeostatic proliferation in IL-4(-) and IL-15(-) hosts but proliferated minimally in IL-7(-) hosts. In addition to homeostatic proliferation, the prolonged survival of naive T cells requires IL-7. Thus, naïve T cells disappeared gradually over a 1-month period upon adoptive transfer into IL-7(-) hosts. These findings indicate that naive T cells depend on IL-7 for survival and homeostatic proliferation.

Regulated expression of nuclear receptor RORγt confers distinct functional fates to NK cell receptor-expressing RORγt(+) innate lymphocytes

Whether the recently identified innate lymphocyte population coexpressing natural killer cell receptors (NKRs) and the nuclear receptor RORγt is part of the NK or lymphoid tissue inducer (LTi) cell lineage remains unclear. By using adoptive transfer of genetically tagged LTi-like cells, we demonstrate that NKR⁻RORγt(+) innate lymphocytes but not NK cells were direct progenitors to NKR(+)RORγt(+) cells in vivo. Genetic lineage tracing revealed that the differentiation of LTi-like cells was characterized by the stable upregulation of NKRs and a progressive loss of RORγt expression. Whereas interleukin-7 (IL-7) and intestinal microbiota stabilized RORγt expression within such NKR-LTi cells, IL-12 and IL-15 accelerated RORγt loss. RORγt(+) NKR-LTi cells produced IL-22, whereas RORγt⁻ NKR-LTi cells released IFN-γ and were potent inducers of colitis. Thus, the RORγt gradient in NKR-LTi cells serves as a tunable rheostat for their functional program. Our data also define a previously unappreciated role of RORγt⁻ NKR-LTi cells for the onset or maintenance of inflammatory bowel diseases.

Bcl-2 rescues T lymphopoiesis in interleukin-7 receptor-deficient mice

Mice lacking functional IL-7 or IL-7R alpha genes are severely deficient in developing thymocytes, T cells, and B cells. IL-7 and IL-7 receptor functions are believed to result in lymphoid cell proliferation and cell maturation, implying signal transduction pathways directly involved in mitogenesis and elaboration of developmentally specific new gene programs. Here, we show that enforced expression of the bcl-2 gene in T-lymphoid cells (by crossing in the Emu-bcl-2 transgene) in IL-7R alpha-deficient mice results in a significant restoration of thymic positive selection and T cell numbers and function. We propose cell survival signals to be the principal function of IL-7R engagement in thymic and T cell development.

Trans-ethnic and Ancestry-Specific Blood-Cell Genetics in 746,667 Individuals from 5 Global Populations

Most loci identified by GWASs have been found in populations of European ancestry (EUR). In trans-ethnic meta-analyses for 15 hematological traits in 746,667 participants, including 184,535 non-EUR individuals, we identified 5,552 trait-variant associations at p < 5 × 10-9, including 71 novel associations not found in EUR populations. We also identified 28 additional novel variants in ancestry-specific, non-EUR meta-analyses, including an IL7 missense variant in South Asians associated with lymphocyte count in vivo and IL-7 secretion levels in vitro. Fine-mapping prioritized variants annotated as functional and generated 95% credible sets that were 30% smaller when using the trans-ethnic as opposed to the EUR-only results. We explored the clinical significance and predictive value of trans-ethnic variants in multiple populations and compared genetic architecture and the effect of natural selection on these blood phenotypes between populations. Altogether, our results for hematological traits highlight the value of a more global representation of populations in genetic studies.

Bcl-2 can rescue T lymphocyte development in interleukin-7 receptor-deficient mice but not in mutant rag-1-/- mice

Signals from cytokine and antigen receptors play crucial roles during lymphocyte development. Mice lacking interleukin-7 receptor are lymphopenic, due to a defect in cell expansion at an early stage of differentiation, and the few mature T cells that develop in IL-7R-/- animals are functionally impaired. Both defects were rescued completely by overexpression of the anti-apoptosis protein Bcl-2. T cell progenitors lacking antigen receptor molecules are also blocked in differentiation and die, presumably because they fail to receive a positive signal via their pre-T cell receptor. Surprisingly, Bcl-2 did not promote survival or differentiation of T cells in rag-1-/- mice. These results provide evidence that blocking apoptosis is the essential function of IL-7R during differentiation and activation of T lymphocytes and that pre-TCR signaling blocks a pathway to apoptosis that is insensitive to Bcl-2.

Variation in interleukin 7 receptor alpha chain (IL7R) influences risk of multiple sclerosis

Multiple sclerosis is a chronic, often disabling, disease of the central nervous system affecting more than 1 in 1,000 people in most western countries. The inflammatory lesions typical of multiple sclerosis show autoimmune features and depend partly on genetic factors. Of these genetic factors, only the HLA gene complex has been repeatedly confirmed to be associated with multiple sclerosis, despite considerable efforts. Polymorphisms in a number of non-HLA genes have been reported to be associated with multiple sclerosis, but so far confirmation has been difficult. Here, we report compelling evidence that polymorphisms in IL7R, which encodes the interleukin 7 receptor alpha chain (IL7Ralpha), indeed contribute to the non-HLA genetic risk in multiple sclerosis, demonstrating a role for this pathway in the pathophysiology of this disease. In addition, we report altered expression of the genes encoding IL7Ralpha and its ligand, IL7, in the cerebrospinal fluid compartment of individuals with multiple sclerosis.

Interleukin 7 is produced by human intestinal epithelial cells and regulates the proliferation of intestinal mucosal lymphocytes

The interaction of mucosal lymphocytes and intestinal epithelial cells is thought to be important in regulating immune response in the intestinal mucosa, but conclusive evidence is limited. Here we demonstrate the expression of IL-7 mRNA in human intestinal mucosa by combined reverse transcription PCR and Southern blot hybridization. Immunohistochemistry and in situ hybridization confirm the presence of IL-7 in intestinal epithelial cells, especially in epithelial goblet cells. Moreover, IL-7 receptor expression in mucosal lymphocytes is demonstrated by immunohistochemistry and in situ hybridization, as well as by Southern blot and flow cytometric analysis of freshly isolated lamina propria lymphocytes. In contrast, IL-7 receptor could not be detected in the cell surface of freshly isolated PBLs. The functional activity of IL-7 receptor is demonstrated by the utility of recombinant IL-7 to stimulate the growth of lamina propria lymphocytes, and conversely inhibit CD3-dependent proliferation of these cells. In contrast, IL-7 caused no significant increase in DNA synthesis and cell numbers when added to PBLs. These findings suggest that human intestinal epithelial cells and epithelial goblet cells produce IL-7, and locally produced IL-7 may serve as a potent regulatory factor for intestinal mucosal lymphocytes.

Transcriptional reprogramming of mature CD4⁺ helper T cells generates distinct MHC class II-restricted cytotoxic T lymphocytes

TCRαβ thymocytes differentiate into either CD8αβ(+) cytotoxic T lymphocytes or CD4(+) helper T cells. This functional dichotomy is controlled by key transcription factors, including the helper T cell master regulator ThPOK, which suppresses the cytolytic program in major histocompatibility complex (MHC) class II-restricted CD4(+) thymocytes. ThPOK continues to repress genes of the CD8 lineage in mature CD4(+) T cells, even as they differentiate into effector helper T cell subsets. Here we found that the helper T cell fate was not fixed and that mature, antigen-stimulated CD4(+) T cells terminated expression of the gene encoding ThPOK and reactivated genes of the CD8 lineage. This unexpected plasticity resulted in the post-thymic termination of the helper T cell program and the functional differentiation of distinct MHC class II-restricted CD4(+) cytotoxic T lymphocytes.

IL-15 is an essential mediator of peripheral NK-cell homeostasis

Several distinct classes of surface receptors can, on ligand binding, transmit signals that modulate the survival, proliferation, and apoptosis of peripheral B, T, and natural killer (NK) cells. At the population level, dynamic changes in lymphocyte cell numbers are strictly regulated to maintain a steady state, a process referred to as homeostasis. Although several studies have investigated the signals that regulate B- and T-cell homeostasis, little is known about the mechanisms that control the survival and proliferation of peripheral NK cells. Using an adoptive transfer system, we have investigated the role of gammac-dependent cytokines, in particular interleukin 7 (IL-7) and IL-15, and major histocompatibility complex (MHC) class I molecules in peripheral NK-cell homeostasis. We observed that IL-15 plays a dominant role in the survival of peripheral NK cells, via maintenance of the antiapoptotic factor Bcl-2. IL-15 availability, however, also plays an important role because endogenous NK cells in the recipient mice influence the behavior of adoptively transferred NK cells. Finally, although NK cells bear functional inhibitory Ly49 receptors for MHC class I molecules, the presence or absence of specific ligands on host cells did not influence the survival or homeostatic expansion of donor NK cells.

Overexpression of interleukin (IL)-7 leads to IL-15-independent generation of memory phenotype CD8+ T cells

Transgenic (TG) mice expressing a high copy number of interleukin (IL)-7 cDNA under the control of the major histocomaptability complex (MHC) class II promoter display a 10-20-fold increase in total T cell numbers. Here, we show that the increase in T cell numbers in IL-7 TG mice is most apparent at the level of memory phenotype CD44hi CD122hi CD8+ cells. Based on studies with T cell receptor (TCR) TG mice crossed to IL-7 TG mice, increased levels of IL-7 may provide costimulation for TCR recognition of self-MHC ligands and thus cause naive CD8+ cells to proliferate and differentiate into memory phenotype cells. In addition, a marked increase in CD44hi CD122hi CD8+ cells was found in IL-7 TG IL-15(-) mice. Since these cell are rare in normal IL-15(-) mice, the dependency of memory phenotype CD8+ cells on IL-15 can be overcome by overexpression of IL-7.

Roles for common cytokine receptor gamma-chain-dependent cytokines in the generation, differentiation, and maturation of NK cell precursors and peripheral NK cells in vivo

NK cells differentiate in adult mice from bone marrow hemopoietic progenitors. Cytokines, including those that signal via receptors using the common cytokine receptor gamma-chain (gamma(c)), have been implicated at various stages of NK cell development. We have previously described committed NK cell precursors (NKPs), which have the capacity to generate NK cells, but not B, T, erythroid, or myeloid cells, after in vitro culture or transfer to a fetal thymic microenvironment. NKPs express the CD122 Ag (beta chain of the receptors for IL-2/IL-15), but lack other mature NK markers, including NK1.1, CD49b (DX5), or members of the Ly49 gene family. In this report, we have analyzed the roles for gamma(c)-dependent cytokines in the generation of bone marrow NKP and in their subsequent differentiation to mature NK cells in vivo. Normal numbers of NKPs are found in gamma(c)-deficient mice, suggesting that NK cell commitment is not dependent on IL-2, IL-4, IL-7, IL-9, IL-15, or IL-21. Although IL-2, IL-4, and IL-7 have been reported to influence NK cell differentiation, we find that mice deficient in any or all of these cytokines have normal NK cell numbers, phenotype, and effector functions. In contrast, IL-15 plays a dominant role in early NK cell differentiation by maintaining normal numbers of immature and mature NK cells in the bone marrow and spleen. Surprisingly, the few residual NK cells generated in absence of IL-15 appear relatively mature, expressing a variety of Ly49 receptors and demonstrating lytic and cytokine production capacity.

Recent immune status determines the source of antigens that drive homeostatic T cell expansion

Homeostatic proliferation of naive T cells transferred to T cell-deficient syngeneic mice is driven by low-affinity self-MHC/peptide ligands and the cytokine IL-7. In addition to homeostatic proliferation, a subset of naive T cells undergoes massive proliferation in chronically immunodeficient hosts, but not in irradiated normal hosts. Such rapid T cell proliferation occurs largely independent of homeostatic factors, because it was apparent in the absence of IL-7 and in T cell-sufficient hosts devoid of functional T cell immunity. Strikingly, immunodeficient mice raised under germfree conditions supported only slow homeostatic proliferation, but not the marked T cell proliferation observed in conventionally raised immunodeficient mice. Thus, polyclonal naive T cell expansion in T cell-deficient hosts can be driven predominantly by either self-Ags or foreign Ags depending on the host's previous state of T cell immunocompetency.

Arrested B lymphopoiesis and persistence of activated B cells in adult interleukin 7(-/)- mice

Interleukin 7 is a crucial factor for the development of murine T and B lymphocytes. We now report that, in the absence of interleukin 7, B lymphocyte production takes place exclusively during fetal and perinatal life, ceasing after 7 wk of age. In peripheral organs, however, the pool of B lymphocytes is stable throughout adult life and consists only of cells that belong to the B1 and marginal zone (MZ) compartments. This is accompanied by a 50-fold increase in the frequency of immunoglobulin (Ig)M- and IgG-secreting cells, and the concentration of serum immunoglobulins is increased three- to fivefold. Both the MZ phenotype and the increase in serum IgM are T cell independent. These findings reveal a previously undescribed pathway of B lymphopoiesis that is active in early life and is interleukin 7 independent. This pathway generates B1 cells and a normal sized MZ B lymphocyte compartment.

Interleukin 7 induces CD4+ T cell-dependent tumor rejection

The potential of interleukin 7 (IL-7) to induce an antitumor response in vivo was analyzed. Therefore, the IL-7 gene was expressed in the plasmacytoma cell line J558L. Although the growth of IL-7-producing cells was not retarded in vitro, the IL-7-producing cells were completely rejected upon injection into mice. Tumor rejection was observed only in syngeneic but not in nude mice. The tumor-suppressive effect could be abolished by the parallel injection of an anti-IL-7 monoclonal antibody. Immunohistochemical analysis revealed IL-7-dependent infiltration of the tumor tissue by CD4+ and CD8+ T lymphocytes, and also type 3 complement receptor-positive (CR3+) cells, predominantly macrophages. Depletion of T cell subsets in tumor-bearing mice showed the absolute dependence of the antitumor response on CD4+ cells, whereas tumor rejection was unaffected by depletion of CD8+ cells. In addition to CD4+ cells, CR3+ cells were also needed for tumor rejection. The antitumor effect of IL-7 was confirmed by expression of the IL-7 gene in a second tumor cell line of different cellular origin. Together, our results demonstrate that a high local IL-7 concentration at the tumor site obtained by tumor cell-targeted gene transfer leads to tumor rejection involving a cellular mechanism that seems to be different from the ones observed in analogous experiments with other cytokines.

Human myeloma cells stimulate the receptor activator of nuclear factor-kappa B ligand (RANKL) in T lymphocytes: a potential role in multiple myeloma bone disease

The biologic mechanisms involved in the pathogenesis of multiple myeloma (MM) bone disease are not completely understood. Recent evidence suggests that T cells may regulate bone resorption through the cross-talk between the critical osteoclastogenetic factor, receptor activator of nuclear factor-kappaB ligand (RANKL), and interferon gamma (IFN-gamma) that strongly suppresses osteoclastogenesis. Using a coculture transwell system we found that human myeloma cell lines (HMCLs) increased the expression and secretion of RANKL in activated T lymphocytes and similarly purified MM cells stimulated RANKL production in autologous T lymphocytes. In addition, either anti-interleukin 6 (anti-IL-6) or anti-IL-7 antibody inhibited HMCL-induced RANKL overexpression. Consistently, we demonstrated that HMCLs and fresh MM cells express IL-7 mRNA and secrete IL-7 in the presence of IL-6 and that bone marrow (BM) IL-7 levels were significantly higher in patients with MM. Moreover, we found that the release of IFN-gamma by T lymphocytes was reduced in presence of both HMCLs and purified MM cells. Furthermore, in a stromal cell-free system, osteoclastogenesis was stimulated by conditioned medium of T cells cocultured with HMCLs and inhibited by recombinant human osteoprotegerin (OPG; 100 ng/mL to 1 microg/mL). Finally, RANKL mRNA was up-regulated in BM T lymphocytes of MM patients with severe osteolytic lesions, suggesting that T cells could be involved at least in part in MM-induced osteolysis through the RANKL overexpression.

Interleukin 7 signaling in dendritic cells regulates the homeostatic proliferation and niche size of CD4+ T cells

Interleukin 7 (IL-7) and T cell antigen receptor signals have been proposed to be the main drivers of homeostatic T cell proliferation. However, it is not known why CD4(+) T cells undergo less-efficient homeostatic proliferation than CD8(+) T cells do. Here we show that systemic IL-7 concentrations increased during lymphopenia because of diminished use of IL-7 but that IL-7 signaling on IL-7 receptor-alpha-positive (IL-7Ralpha(+)) dendritic cells (DCs) in lymphopenic settings paradoxically diminished the homeostatic proliferation of CD4(+) T cells. This effect was mediated at least in part by IL-7-mediated downregulation of the expression of major histocompatibility complex class II on IL-7Ralpha(+) DCs. Our results indicate that IL-7Ralpha(+) DCs are regulators of the peripheral CD4(+) T cell niche and that IL-7 signals in DCs prevent uncontrolled CD4(+) T cell population expansion in vivo.

Mechanisms of rejection induced by tumor cell-targeted gene transfer of interleukin 2, interleukin 4, interleukin 7, tumor necrosis factor, or interferon gamma

Interleukin (IL)-2, IL-4, IL-7, tumor necrosis factor (TNF), or interferon-gamma (IFN-gamma) has been shown to be able to induce tumor rejection if produced locally by the tumor cells after gene transfer. To analyze whether the cellular rejection mechanisms are different or redundant we have expressed the cytokines in the same tumor cell line (J558L). Cell depletion experiments revealed that all cytokines required CD8+ T cells for complete long-term tumor eradication, although effective but transient host-dependent tumor suppression was also observed in the complete absence of CD8+ T cells. The transient tumor suppression induced by IL-2, IL-4, TNF, or IFN-gamma was also operative in nude and severe combined immunodeficient mice, whereas only tumor suppression induced by IL-7 was dependent on the presence of CD4+ T cells and was not evident in nude mice. The T-cell-independent effector arm of IL-2 and IFN-gamma but not IL-4 and TNF was mediated in part by natural killer cells. The transience of tumor suppression in the absence of T cells reflected loss of cytokine production in the case of TNF, IL-2, and IL-4 but not IFN-gamma. Immunohistologic analysis revealed all cytokine-producing tumors to be heavily infiltrated by macrophages. IL-4 and IL-7 tumors additionally contained eosinophils. The infiltration by T cells did not necessarily reflect their contribution to tumor rejection. Thus, the different cytokines activate heterogeneous transient tumor-suppressive mechanisms but always require CD8+ T cells for complete tumor rejection.

Ectopic lymphoid-organ development occurs through interleukin 7-mediated enhanced survival of lymphoid-tissue-inducer cells

Development of Peyer's patches and lymph nodes requires the interaction between CD4+ CD3- IL-7Ralpha+ lymphoid-tissue inducer (LTi) and VCAM-1+ organizer cells. Here we showed that by promoting their survival, enhanced expression of interleukin-7 (IL-7) in transgenic mice resulted in accumulation of LTi cells. With increased IL-7 availability, de novo formation of VCAM-1+ Peyer's patch anlagen occurred along the entire fetal gut resulting in a 5-fold increase in Peyer's patch numbers. IL-7 overexpression also led to formation of multiple organized ectopic lymph nodes and cecal patches. After immunization, ectopic lymph nodes developed normal T cell-dependent B cell responses and germinal centers. Mice overexpressing IL-7 but lacking either RORgamma, a factor required for LTi cell generation, or lymphotoxin alpha1beta2 had neither Peyer's patches nor ectopic lymph nodes. Therefore, by controlling LTi cell numbers, IL-7 can regulate the formation of both normal and ectopic lymphoid organs.

Interleukin 7 transgenic mice develop chronic colitis with decreased interleukin 7 protein accumulation in the colonic mucosa

We have demonstrated that intestinal epithelial cells produce interleukin 7 (IL-7), and IL-7 serves as a potent regulatory factor for proliferation of intestinal mucosal lymphocytes expressing functional IL-7 receptor. To clarify the mechanism by which locally produced IL-7 regulates the mucosal lymphocytes, we investigated IL-7 transgenic mice. Here we report that transgenic mice expressing murine IL-7 cDNA driver by the SRalpha promoter developed chronic colitis in concert with the expression of SRalpha/IL-7 transgene in the colonic mucosa. IL-7 transgenic but not littermate mice developed chronic colitis at 4-12 wk of age, with histopathological similarity to ulcerative colitis in humans. Southern blot hybridization and competitive PCR demonstrated that the expression of IL-7 messenger RNA was increased in the colonic mucosal lymphocytes but not in the colonic epithelial cells. IL-7 protein accumulation was decreased in the goblet cell-depleted colonic epithelium in the transgenic mice. Immunohistochemical and cytokine production analysis showed that lymphoid infiltrates in the lamina propria were dominated by T helper cell type 1 CD4+ T cells. Flow cytometric analysis demonstrated that CD4+ intraepithelial T cells were increased, but T cell receptor gamma/delta T cells and CD8alpha/alpha cells were not increased in the area of chronic inflammation. Increased IL-7 receptor expression in mucosal lymphocytes was demonstrated in the transgenic mice. These findings suggest that chronic inflammation in the colonic mucosa may be mediated by dysregulation of colonic epithelial cell-derived IL-7, and this murine model of chronic colitis may contribute to the understanding of the pathogenesis of human inflammatory bowel disease.

Proinflammatory mediator-induced reversal of CD4+,CD25+ regulatory T cell-mediated suppression in rheumatoid arthritis

OBJECTIVE

We previously demonstrated that CD4+,CD25+ regulatory T (Treg) cells are present in increased numbers in the synovial fluid (SF) of rheumatoid arthritis (RA) patients and display enhanced suppressive activity as compared with their peripheral blood (PB) counterparts. Despite the presence of these immunoregulatory cells in RA, chronic inflammation persists. The purpose of the present study was to investigate whether particular proinflammatory mediators that are associated with RA could abrogate CD4+,CD25+ Treg-mediated suppression.

METHODS

Monocyte phenotype was determined by flow cytometry and cytokine levels by enzyme-linked immunosorbent assay. Magnetically sorted CD4+,CD25- and CD4+,CD25+ T cells derived from the PB and SF obtained from RA patients were stimulated alone or in coculture with anti-CD3 monoclonal antibody (mAb) and autologous antigen-presenting cells, in the absence or presence of anti-CD28 mAb or the proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha), or IL-7.

RESULTS

Monocytes from the SF of RA patients displayed increased expression of HLA class II molecules, CD80, CD86, and CD40 as compared with PB-derived monocytes, indicating their activated status. Mimicking this increased costimulatory potential, addition of anti-CD28 mAb to cocultures of CD4+,CD25- and CD4+,CD25+ T cells resulted in reduced CD4+,CD25+ Treg-mediated suppression in both PB and SF. Furthermore, IL-7 and, to a limited extent, TNFalpha, both of which are produced by activated monocytes and were detected in SF, abrogated the CD4+,CD25+ Treg-mediated suppression. In contrast, IL-6 did not influence Treg-mediated suppression.

CONCLUSION

Our findings suggest that the interaction of CD4+,CD25+ Treg cells with activated monocytes in the joint might lead to diminished suppressive activity of CD4+,CD25+ Treg cells in vivo, thus contributing to the chronic inflammation in RA.

Increased expression of lymphocyte-derived cytokines in benign hyperplastic prostate tissue, identification of the producing cell types, and effect of differentially expressed cytokines on stromal cell proliferation

BACKGROUND

Benign prostatic hyperplasia (BPH) frequently exhibit infiltration of CD4 (+)/CD45RO (+) memory-T-lymphocytes. Expression and impact of lymphocyte-derived growth factors on prostatic stromal cell (PSC) growth were investigated. METHODS; Lymphokine synthesis in normal prostate tissues (n = 3), BPH-tissues (n = 13), BPH-derived T-cells (n = 6), BPH-derived epithelial cells (BPH-EC) (n = 5), normal prostate-derived (n = 3) and BPH-derived stromal cell lines (BPH-SC) (n = 6), and prostate cancer (CaP) lines (n = 3) was analyzed by RT-PCR and Southern-blotting. The effect of interleukin (IL)-2, -4, -7, and interferon-gamma (IFN-gamma) on normal and BPH-SC growth was investigated by (3)H-thymidine incorporation assays.

RESULTS

All BPH-tissues and, to a lesser degree, normal prostates, expressed significant amounts of IFN-gamma mRNA. However, only BPH-tissues contained IL-2 and IL-4 mRNA (ratio: 10:13). BPH-T-cell lines were heterogeneous in composition and expressed significant amounts of IFN-gamma, IL-2, and IL-4 mRNA. Low level expression of these lymphokines was also observed in BPH-EC, CaP lines, and PSC lines. IL-2, -7 and IFN-gamma stimulated the proliferation of BPH-PSC lines but not that of normal PSC, while IL-4 inhibited BPH-PSC growth.

CONCLUSIONS

Chronic inflammation may induce an increased growth pattern of fibromuscular tissue in BPH similar to that of wound healing.

Molecular characterization of the mouse involuted thymus: aberrations in expression of transcription regulators in thymocyte and epithelial compartments

Despite playing a critical role in the development of naive T cells, the thymus is involuted with age. Whether a single age-associated defect or multiple aberrations contribute to thymic involution remains controversial. Here, we determined molecular aberrations in the thymocyte and epithelium compartments of the aging thymus. We demonstrated that total thymocyte numbers declined with a stepwise kinetics; clear demarcations occurred at 1.5, 3, 12 and 22 months of age. By quantitative PCR, a 2.4-fold reduction in the copies of signal joint TCR-excised circle (sjTREC)/10(5) thymocytes was first detected at 3 months; no further reduction observed thereafter. Nevertheless, the combined reductions in thymocyte numbers and sjTREC/10(5) cells caused a 7-fold decrease in sjTREC/thymus by 3 months, 21-fold by 18 months and 72-fold by 22 months as compared to 1 month. We showed aberration in expression of E2A, a transcription regulator critical for TCR beta rearrangement. While E2A expression declined 3-fold by 3 months and 18-fold by 7 months, expression of LMO2, a negative regulator of E2A activities, increased 5-fold by 18 months. Interestingly, expression of pre-T alpha and its transcriptional regulator HEB were not reduced with age. Furthermore, keratin-8 expression, specific for cortical thymic epithelium, declined 3-fold by 7 months and remained stable thereafter. In contrast, Foxn1 expression was reduced 3-fold by 3 months, 16-fold by 12 months and 37-fold by 18 months. IL-7 expression was not reduced until 7 months and reached 15-fold reduction by 22 months. Thus, the data demonstrate that thymic involution results not from a single defect, but culminates from an array of molecular aberrations in both the developing thymocytes and thymic epithelials.