Abstract A02: Oncogenic drivers of lung cancer induce production of CCL5 and recruitment of regulatory T-cells

Lung cancer development is driven by the expression of mutant oncogenes, with EGFR and KRAS being the most frequent mutations in lung adenocarcinoma. However, additional factors may influence lung tumor development and progression, including the balance of antitumor immune effector cells and pro-tumorigenic immune suppressor cells within the lung and lung tumor microenvironment. Tumor cells can evade immune attack by producing cytokines that recruit immune modulatory cells, such as regulatory T cells (Tregs), that promote a localized immune suppressive environment We hypothesized that oncogene signaling regulates the production of cytokines by tumor cells at the earliest stages of transformation that can recruit immune suppressive cells and promote lung tumour development. We used CIBERSORT-based analysis of gene expression data to quantify 22 different immune cell types from over 300 human lung adenocarcinomas and 100 matched normal lung tissues. We found that Tregs were significantly enriched in early-stage lung adenocarcinoma tumors compared to matched normal tissue from the same patient, and validated these findings with immunohistochemistry staining of lung sections. To identify cytokines that could recruit Tregs early in lung tumorigenesis, we used normal cells expressing doxycycline-inducible wild-type EGFR, mutant EGFRL858R or mutant KRASG12V. Secreted cytokines were quantified using a multiplex LUMINEX assay with subsequent validation by ELISA. Induction of EGFRL858R and KRASG12V expression in normal cells rapidly increased the production of CCL5 (RANTES), as did expression of wild-type EGFR in the presence of exogenous EGF. To elucidate the mechanism of oncogene-driven CCL5 secretion, we treated lung cancer cells harboring EGFR or KRAS mutations with a MEK inhibitor (trametinib) to disrupt oncogenic signaling downstream of EGFR and KRAS. In KRAS mutant lung cancer cells, treatment with trametinib decreased CCL5 production and inhibited both ERK and AKT signaling. To determine if oncogene-driven cytokines could induce migration of Tregs ex vivo, we used a trans-well assay with conditioned media from cells expressing doxycycline inducible EGFRL858R or KRASG12V. Conditioned media from EGFRL858R and KRASG12V-expressing cells induced Treg migration, which was mitigated by the addition of an anti-CCL5 antibody. These data indicate that oncogenic EGFR and KRAS signaling regulates expression of CCL5 in lung tumor cells, and that CCL5-mediated Treg recruitment to lung tumors may occur in early stages of lung tumor development. Therefore, targeted inhibition of CCL5, Tregs, and/or oncogenic EGFR and KRAS signaling may represent therapeutic strategies to block recruitment and function of immunosuppressive Tregs during lung tumor development.

Citation Format: Elizabeth Franks, Elizabeth C. Halvorsen, Etienne Melese, Unni Arun, Jenna L. Collier, Bryant T. Harbourne, Min Hee Oh, Lam Vivian, Gerry Krystal, John C. English, Wan L. Lam, Stephen Lam, Ninan Abraham, Kevin L. Bennewith, William W. Lockwood. Oncogenic drivers of lung cancer induce production of CCL5 and recruitment of regulatory T-cells [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr A02.

Paracrine rather than systemic glucocorticoids are biologically active in the thymus

Thymocyte positive and negative selection are critical for generation of a competent and self-tolerant T cell repertoire. Glucocorticoids (GCs) protect thymocytes from T cell receptor (TCR)-induced death, and thymocyte-specific GC receptor (GR) deletion amplifies negative selection, weakening the TCR repertoire. Circulating GCs are secreted by the adrenals, but levels fluctuate widely with time of day and in response to stressors. To avoid such variation, thymus GCs might be regulated independently of the adrenals, as thymic epithelial cells (TECs) and possibly thymocytes express GC-synthetic enzymes. Whether local GC production is sufficient to affect thymocyte development in the presence of adrenal GCs, however, is unknown. Here, we have found that corticosterone, the major mouse GC, was locally elevated in the thymus compared to the blood, and that cultured thymus produced corticosterone from endogenous substrates via GC-synthetic enzyme activity. To test the source and importance of local GC synthesis in vivo, we generated mice with targeted deletion of the GC-synthetic enzyme Cyp11b1 in TECs (Cyp11b1foxn1-Cre) or thymocytes (Cyp11b1lck-Cre). As a measure of GC signaling we quantified thymocyte expression of the GC-responsive gene Gilz. Gilz mRNA was normal in Cyp11b1lck-Cre but reduced in Cyp11b1foxn1-Cre thymocytes, with a reduction equivalent to that in GR-deficient thymocytes. Basal GR signaling is thus driven overwhelmingly by TEC-rather than adrenal-derived corticosterone. These findings demonstrate the importance of paracrine GC function in vivo, and are consistent with a role for paracrine GCs in thymocyte selection.

Emerging roles of T helper 17 and regulatory T cells in lung cancer progression and metastasis

Lung cancer is a leading cause of cancer-related deaths worldwide. Lung cancer risk factors, including smoking and exposure to environmental carcinogens, have been linked to chronic inflammation. An integral feature of inflammation is the activation, expansion and infiltration of diverse immune cell types, including CD4⁺ T cells. Within this T cell subset are immunosuppressive regulatory T (Treg) cells and pro-inflammatory T helper 17 (Th17) cells that act in a fine balance to regulate appropriate adaptive immune responses.In the context of lung cancer, evidence suggests that Tregs promote metastasis and metastatic tumor foci development. Additionally, Th17 cells have been shown to be an integral component of the inflammatory milieu in the tumor microenvironment, and potentially involved in promoting distinct lung tumor phenotypes. Studies have shown that the composition of Tregs and Th17 cells are altered in the tumor microenvironment, and that these two CD4⁺ T cell subsets play active roles in promoting lung cancer progression and metastasis.We review current knowledge on the influence of Treg and Th17 cells on lung cancer tumorigenesis, progression, metastasis and prognosis. Furthermore, we discuss the potential biological and clinical implications of the balance among Treg/Th17 cells in the context of the lung tumor microenvironment and highlight the potential prognostic function and relationship to metastasis in lung cancer.

Lymphoid organs of neonatal and adult mice preferentially produce active glucocorticoids from metabolites, not precursors

Glucocorticoids (GCs) are circulating adrenal steroid hormones that coordinate physiology, especially the counter-regulatory response to stressors. While systemic GCs are often considered immunosuppressive, GCs in the thymus play a critical role in antigen-specific immunity by ensuring the selection of competent T cells. Elevated thymus-specific GC levels are thought to occur by local synthesis, but the mechanism of such tissue-specific GC production remains unknown. Here, we found metyrapone-blockable GC production in neonatal and adult bone marrow, spleen, and thymus of C57BL/6 mice. This production was primarily via regeneration of adrenal metabolites, rather than de novo synthesis from cholesterol, as we found high levels of gene expression and activity of the GC-regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), but not the GC-synthetic enzyme CYP11B1. Furthermore, incubation with physiological concentrations of GC metabolites (11-dehydrocorticosterone, prednisone) induced 11β-HSD1- and GC receptor-dependent apoptosis (caspase activation) in both T and B cells, showing the functional relevance of local GC regeneration in lymphocyte GC signaling. Local GC production in bone marrow and spleen raises the possibility that GCs play a key role in B cell selection similar to their role in T cell selection. Our results also indicate that local GC production may amplify changes in adrenal GC signaling, rather than buffering against such changes, in the immune system.

Topical CpG Oligodeoxynucleotide Adjuvant Enhances the Adaptive Immune Response against Influenza A Infections

Current influenza vaccines generate humoral immunity, targeting highly variable epitopes and thus fail to achieve long-term protection. T cells recognize and respond to several highly conserved epitopes across influenza serotypes. A strategy of raising strong cytotoxic T cell memory responses to epitopes conserved across serotypes would provide cross serotype protection, eliminating the need for annual vaccination. We explored the adjuvant potential of epicutaneous (ec) and subcutaneous (sc) delivery of CpG oligodeoxynucleotide in conjunction with sc protein immunization to improve protection against influenza A virus (IAV) infections using a mouse model. We found enhanced long-term protection with epicutaneous CpG ODN (ecCpG) compared to subcutaneous CpG ODN (scCpG) as demonstrated by reduced viral titers in the lungs. This correlated with increased antigen-specific CD8 T cells in the airways and the lungs. The memory T cell response after immunization with ecCpG adjuvant was comparable to memory response by priming with IAV infection in the lungs. In addition, ecCpG was more efficient than scCpG in inducing the generation of IFN-γ producing CD4 T cells. The adjuvant effect of ecCpG was accompanied with its ability to modulate tissue-homing molecules on T cells that may direct them to the site of infection. Together, this work provides evidence for using ecCpG to induce strong antibody and memory T cell responses to confer protection against IAV infection.

‘Innate and T lymphocyte developmental pathways independent of Common lymphoid progenitors’

Lymphocytes are believed to develop from a population of committed lymphoid progenitors termed common lymphoid progenitors (CLPs). However, upstream lymphoid progenitors termed lymphoid-primed multi-potent progenitors (LMPPs) are more efficient than CLPs in differentiating into group 2 innate lymphoid cells (ILC2s) and T cells, suggesting that alternative pathways for the development of these cells exist. In this study, we divided LMPPs into CD127− (LMPP-s) and CD127+ (LMPP+s) subsets and compared them with Ly6D+ and Ly6D− CLPs. Adult LMPP+s differentiated into ILCs and T cells more rapidly and efficiently than other progenitors in transplantation assays. Development of ILC2s and T cells is highly active during neonatal period. In this period CLPs are rare and, unlike prominent neonatal LMPP+s, do not efficiently differentiate into ILC2s and T cells. ILC2s generated in neonates persist in adults. These results suggest that the majority of ILCs and T cells develop from LMPP+s via CLP-independent pathways.

Common-Lymphoid-Progenitor-Independent Pathways of Innate and T Lymphocyte Development

All lymphocytes are thought to develop from common lymphoid progenitors (CLPs). However, lymphoid-primed multipotent progenitors (LMPPs) are more efficient than CLPs in differentiating into T cells and group 2 innate lymphoid cells (ILC2s). Here, we have divided LMPPs into CD127(-) (LMPP-s) and CD127(+) (LMPP+s) subsets and compared them with Ly6D(-) and Ly6D(+) CLPs. Adult LMPP+s differentiated into T cells and ILCs more rapidly and efficiently than other progenitors in transplantation assays. The development of T cells and ILC2s is highly active in the neonatal period. Neonatal CLPs are rare and, unlike prominent neonatal LMPP+s, do not efficiently differentiate into T cells and ILC2s. ILC2s generated in the neonatal period are long lived and persist in adult tissues. These results suggest that some ILCs and T cells may develop from LMPP+s via CLP-independent pathways.

Survival of effector CD8+ T cells during influenza infection is dependent on autophagy

The activation and expansion of effector CD8(+) T cells are essential for controlling viral infections and tumor surveillance. During an immune response, T cells encounter extrinsic and intrinsic factors, including oxidative stress, nutrient availability, and inflammation, that can modulate their capacity to activate, proliferate, and survive. The dependency of T cells on autophagy for in vitro and in vivo activation, expansion, and memory remains unclear. Moreover, the specific signals and mechanisms that activate autophagy in T effector cells and their survival are not known. In this study, we generated a novel inducible autophagy knockout mouse to study T cell effector responses during the course of a virus infection. In response to influenza infection, Atg5(-/-) CD8(+) T cells had a decreased capacity to reach the peak effector response and were unable to maintain cell viability during the effector phase. As a consequence of Atg5 deletion and the impairment in effector-to-memory cell survival, mice fail to mount a memory response following a secondary challenge. We found that Atg5(-/-) effector CD8(+) T cells upregulated p53, a transcriptional state that was concomitant with widespread hypoxia in lymphoid tissues of infected mice. The onset of p53 activation was concurrent with higher levels of reactive oxygen species (ROS) that resulted in ROS-dependent apoptotic cell death, a fate that could be rescued by treating with the ROS scavenger N-acetylcysteine. Collectively, these results demonstrate that effector CD8(+) T cells require autophagy to suppress cell death and maintain survival in response to a viral infection.

Steroid profiling reveals widespread local regulation of glucocorticoid levels during mouse development

Glucocorticoids (GCs) are produced by the adrenal glands and circulate in the blood to coordinate organismal physiology. In addition, different tissues may independently regulate their local GC levels via local GC synthesis. Here, we find that in the mouse, endogenous GCs show tissue-specific developmental patterns, rather than mirroring GCs in the blood. Using solid-phase extraction, HPLC, and specific immunoassays, we quantified endogenous steroids and found that in tissues of female and male mice, (1) local GC levels can be much higher than systemic GC levels, (2) local GCs follow age-related patterns different from those of systemic GCs, and (3) local GCs have identities different from those of systemic GCs. For example, whereas corticosterone is the predominant circulating adrenal GC in mice, high concentrations of cortisol were measured in neonatal thymus, bone marrow, and heart. The presence of cortisol was confirmed with liquid chromatography-tandem mass spectrometry. In addition, gene expression of steroidogenic enzymes was detected across multiple tissues, consistent with local GC production. Our results demonstrate that local GCs can differ from GCs in circulating blood. This finding suggests that steroids are widely used as local (paracrine or autocrine) signals, in addition to their classic role as systemic (endocrine) signals. Local GC regulation may even be the norm, rather than the exception, especially during development.

The survival and differentiation of pro-B and pre-B cells in the bone marrow is dependent on IL-7Rα Tyr449

IL-7 is critical for murine T and B cell development and survival and plays a significant role in lymphoblastic leukemia in both humans and mice. We evaluated the role of the IL-7Rα Tyr(449) cytoplasmic SH2-binding motif in IL-7-mediated B cell development using a knock-in mouse with a Tyr to Phe mutation (IL-7Rα(449F/449F) mouse). IL-7Rα(449F/449F) and IL-7Rα(-/-) mice showed no defect in the number of pre-pro-B cells, although IL-7Rα(449F/449F) mice had decreased Ebf1 in pre-pro-B cells and impairment in B cell-committed CLPs. We identified that IL-7Rα Tyr(449) was critical for both pro-B and pre-B stages of development in the bone marrow. IL-7Rα(449F/449F) and IL-7Rα(-/-) mice had comparable precursor B cell defects, indicating that signaling from the IL-7Rα required this motif. Although the defect in IL-7Rα(449F/449F) pro-B cells was associated with loss of STAT5 activation and diminished expression of Mcl1, this was not rescued by overexpression of Bcl-2. IL-7Rα(449F/449F) and IL-7Rα(-/-) pre-B cells also showed defective cyto-Igμ and CD25 expression, associated with reduced levels of Rag1, Rag2, and Irf4. Pre-B cells from IL-7Rα(449F/449F) mice also failed to proliferate, perhaps as a result of the failure to rearrange Igμ. Our data suggest that IL-7Rα Tyr(449) was essential for IL-7Rα signaling in bone marrow B cell development and survival.

The development and survival but not function of follicular B cells is dependent on IL-7Rα Tyr449 signaling. (CCR1P.242)

IL-7 is a critical cytokine for lymphocyte development but its role in B cells is less well characterized. Using a knock-in mouse with a Tyr to Phe mutation at position 449 (IL-7Rα449F/449F mice) within the cytoplasmic domain of IL-7Rα, we evaluated the role of this YxxM motif in spleen B cells. IL-7Rα449F/449F mice had reduced numbers and increased death of follicular B cells compared to WT, but had significantly more follicular cells than IL-7Rα-/-. The death of IL-7Rα449F/449F follicular cells was not due to a failure to respond to BAFF or lower levels of BAFF. Marginal zone B cells were unaffected in IL-7Rα449F/449F mice. A role for TSLP was ruled out, as TSLPR-/- mice had an identical B cell phenotype to wild-type mice. Bone marrow chimeras and the absence of IL-7Rα on B cells suggested that IL-7 did not directly regulate mature B cells, but that an IL-7-responsive cell was influencing B cells. IL-7 was also critical at the checkpoint between the T1 and T2 stages in the spleen. We tested the functional responses of IL-7Rα449F/449F mice and found no difference in antibody responses to T-dependent or T-independent antigens, or to Influenza/A. IL-7 was important for generation of antibody responses to the intestinal worm H. polygyrus and for naive levels of IgA. Our data shows that IL-7 regulates follicular B cell numbers and survival in a cell-extrinsic manner, via a bone-marrow derived cell, but is not critical for antibody production outside the gut.

The development and survival but not function of follicular B cells is dependent on IL-7Rα Tyr449 signaling

IL-7 is a critical cytokine for lymphocyte development. Recent work has highlighted critical roles for IL-7 signaling in mature T cell homeostasis and function, but its role in B cells is less well characterized. Using a knock-in mouse possessing a Tyr to Phe mutation at position 449 (IL-7Rα(449F/449F) mice) within the cytoplasmic SH2-binding motif of IL-7Rα, we evaluated the role of IL-7Rα Y449 motif in spleen B cells. IL-7Rα(449F/449F) mice had reduced numbers and increased death of follicular B cells compared to WT, but had significantly more follicular cells than IL-7Rα(-/-). The death of IL-7Rα(449F/449F) follicular cells was not due to a failure to respond to BAFF or lower levels of BAFF, a critical B cell survival factor. Marginal zone B cells were unaffected by the IL-7Rα(449F/449F) mutation. Any role for TSLP was ruled out, as TSLPR(-/-) mice had an identical B cell phenotype to wild-type mice. Bone marrow chimeras and the absence of IL-7Rα on B cells suggested that IL-7 did not directly regulate mature B cells, but that an IL-7-responsive cell was influencing B cells. IL-7 was also critical at the checkpoint between the T1 and T2 stages in the spleen. IL-7Rα(-/-) mice fail to develop T2 cells, but IL-7Rα(449F/449F) show a reduction compared to WT but not complete absence of T2 cells. We also tested the functional responses of IL-7Rα(449F/449F) to antigens and infection and found no difference in antibody responses to T-dependent or T-independent antigens, or to Influenza/A. IL-7 was important for generation of antibody responses to the intestinal worm H. polygyrus and for naive levels of IgA. Taken together, this suggests that IL-7 regulates follicular B cell numbers and survival in a cell-extrinsic manner, via a bone-marrow derived cell, but is not critical for antibody production outside the gut.

Topical CpG adjuvant enhances immune response to subcutaneous antigen by modulating the cutaneous lymph node environment (P4267)

Current vaccines are mainly administered by intramuscular route but the skin harbors many immune cells and can be used as a site of immunization. Topical CpG oligodeoxynucleotide (ODN), a Toll-like receptor 9 (TLR9) agonist, improves humoral and cell-mediated immune responses to locally injected protein-based vaccines in mice but the mechanisms are still unclear. Topical CpG ODN is internalized by CD11c+ cells that are detected within the skin draining lymph nodes (SLN) at 48 hours post treatment. Ablation of TLR9 in the hematopoietic compartment of bone marrow chimeric mice abrogates antigen-specific CD8+ T cells production. TLR9 ablation in the stromal compartment also decreases topical CpG adjuvant effect. Topical CpG ODN differentially modulates the environment of SLN compared to subcutaneous administration within 24 hours of treatment (with 4-7 fold increased expression of 4 genes: Ccl4, Cxcl3, Ifng and Il11). A higher proportion of antigen-specific CD4+ T cells in the SLN express tissue-homing molecules (P- and E-selectin ligand) when adjuvant is administered topically compared to subcutaneously. Egress of lymphocytes from SLN is necessary for optimal CpG adjuvant effect using a contact hypersensitivity model. We propose that topical CpG ODN activates stromal cells as well as hematopoietic-derived cells in the skin, to subsequently modulate the environment of SLN. These changes enhance protective humoral and cell-mediated immune responses.

Surgical techniques for pelvic floor reconstruction: review of the recent literature

The number of women who will undergo pelvic organ prolapse repair is predicted to increase by almost 50% by 2050. Surgeons need updated knowledge and mastery of pelvic floor reconstruction in order to meet the rising demand for services. This review provides an update on the evidence for the various surgical techniques for anterior, posterior, and apical pelvic organ prolapse, specifically focusing on randomized trials within the last ten years.

Interleukin-7, but not thymic stromal lymphopoietin, plays a key role in the T cell response to influenza A virus

The immune response to viral infection is ideally rapid and specific, resulting in viral clearance and establishment of immune memory. Some viruses such as HIV can evade such responses leading to chronic infection, while others like Influenza A can elicit a severe inflammatory response with immune-related complications including death. Cytokines play a major role in shaping the appropriate outcomes to infection. While Interleukin-7 (IL-7) has a critical role in T and B cell development, treatment with IL-7 has recently been shown to aid the adaptive T cell response in clearance of chronic viral infection. In contrast, the IL-7-related cytokine thymic stromal lymphopoietin (TSLP) has a limited role in lymphocyte development but is important in the immune response to parasitic worms and allergens. The role for these cytokines in the immune response to an acute viral infection is unclear. IL-7 and TSLP share IL-7Rα as part of their heterodimeric receptors with the gamma common chain (γc) and TSLPR, respectively. We investigated the role of IL-7 and TSLP in the primary immune response to influenza A infection using hypomorphic IL-7Rα (IL-7Rα^449F) and TSLPR^−/− mice. We found that IL-7, but not TSLP, plays an important role in control of influenza A virus. We also showed that IL-7 signaling was necessary for the generation of a robust influenza A-specific CD4 and CD8 T cell response and that this requirement is intrinsic to CD8 T cells. These findings demonstrate a significant role for IL-7 during acute viral infection.

Unusual timing of CD127 expression by mouse uterine natural killer cells

Decidualization, a progesterone-dependent process that alters endometrial stromal cells at implantation sites in humans and rodents, is accompanied by a highly regulated, NK cell-dominated leukocyte influx into decidual basalis (DB). Whether uNK cells differentiate from uterine progenitor cells is unknown, as are the mechanisms restricting leukocytes to DB. We asked if cells expressing the early NK lineage marker CD127 (IL-7Rα) occurred in mouse decidua. CD127 was absent from gd6.5 decidual lymphoid cells but became expressed by a mature uNK cell subset in gd10.5 DB. DB and transient myometrial structures (MLAp) that ring maternal blood vessels supplying placentae expressed IL-7 and TSLP, the CD127 ligands, but with differing temporal and spatial patterns. UNK cells expressed TSLPR, and study of gd10.5 implantation sites from mice deleted for IL-7, CD127, or TSLPR suggested that IL-7 and its receptor have physiological roles in limiting expansion of immature uNK cells within MLAp, while the TSLP signaling pathway is used in DB to sustain IFN-γ production from a subset of mature uNK cells. Regionalized, dynamic expression of the additional lymphoid organ stromal markers gp38/podoplanin and ER-TR7, but not CD157, were seen by immunohistochemistry in implantation sites, and DB and MLAp contained transcripts for Aire, a tolerance-promoting factor. These observations suggest that CD127(+) NK lineage progenitors are not present in the early postimplantation period of mouse uterus and that decidualized endometrial stroma has key immunoregulatory properties.

Impaired event memory and recollection in a case of developmental amnesia

A current debate in the literature is whether all declarative memories and associated memory processes rely on the same neural substrate. Here, we show that H.C., a developmental amnesic person with selective bilateral hippocampal volume loss, has a mild deficit in personal episodic memory, and a more pronounced deficit in public event memory; semantic memory for personal and general knowledge was unimpaired. This was accompanied by a subtle difference in impairment between recollection and familiarity on lab-based tests of recognition memory. Strikingly, H.C.'s recognition did not benefit from a levels-of-processing manipulation. Thus, not all types of declarative memory and related processes can exist independently of the hippocampus even if it is damaged early in life.

Elevated IL-7 availability does not account for T cell proliferation in moderate lymphopenia. (104.11)

Lymphopenia-induced proliferation (LIP) is a proliferative program initiated in response to T cell insufficiency caused by acute or chronic immunodepletion. Studies of lymphopenic mice have demonstrated that the cytokine IL-7 and TCR signaling are critical for LIP. We examined how these two factors impact T cell proliferation following transfer into moderately lymphopenic mice. We show here that moderate lymphopenia (~25% of WT lymphocytes) of IL-7Rα knock-in mutant (IL-7Rα449F) mice supports T cell proliferation, although with decreased frequency and kinetics compared to cells transferred to severely lymphopenic (5% of WT) IL-7Rα-/- hosts. Although previous studies have demonstrated that elevated IL-7 levels play an important role in LIP, IL-7 availability was not elevated in IL-7Rα449F mice. However, moderate lymphopenia increased access of transferred T cells to self-peptide presented on antigen presenting cells that can trigger TCR signaling and proliferation. Importantly, we did not detect significant changes in TCR Vβ usage of proliferated T cells recovered from either moderately or severely lymphopenic hosts. Our work demonstrates that polyclonal T cells retain a diverse TCR repertoire following proliferation mediated by either self-peptide/MHC interaction alone or in combination with IL-7, and that T cell reconstitution is most efficient in the presence of increased IL-7 availability.

Glucose stimulates human beta cell replication in vivo in islets transplanted into NOD-severe combined immunodeficiency (SCID) mice

AIMS/HYPOTHESIS

We determined whether hyperglycaemia stimulates human beta cell replication in vivo in an islet transplant model

METHODS

Human islets were transplanted into streptozotocin-induced diabetic NOD-severe combined immunodeficiency mice. Blood glucose was measured serially during a 2 week graft revascularisation period. Engrafted mice were then catheterised in the femoral artery and vein, and infused intravenously with BrdU for 4 days to label replicating beta cells. Mice with restored normoglycaemia were co-infused with either 0.9% (wt/vol.) saline or 50% (wt/vol.) glucose to generate glycaemic differences among grafts from the same donors. During infusions, blood glucose was measured daily. After infusion, human beta cell replication and apoptosis were measured in graft sections using immunofluorescence for insulin, and BrdU or TUNEL.

RESULTS

Human islet grafts corrected diabetes in the majority of cases. Among grafts from the same donor, human beta cell proliferation doubled in those exposed to higher glucose relative to lower glucose. Across the entire cohort of grafts, higher blood glucose was strongly correlated with increased beta cell replication. Beta cell replication rates were unrelated to circulating human insulin levels or donor age, but tended to correlate with donor BMI. Beta cell TUNEL reactivity was not measurably increased in grafts exposed to elevated blood glucose.

CONCLUSIONS/INTERPRETATION

Glucose is a mitogenic stimulus for transplanted human beta cells in vivo. Investigating the underlying pathways may point to mechanisms capable of expanding human beta cell mass in vivo.

CD45 regulates migration, proliferation, and progression of double negative 1 thymocytes

CD45 is a protein tyrosine phosphatase that is expressed on all nucleated hematopoietic cells, from stem cells to memory cells. Although its function in regulating the threshold of Ag receptor signaling is well established, its role in other leukocytes, particularly progenitor cells, is not well defined. In this study, we find CD45 affects early thymocyte development. Examination of the CD4(-)CD8(-) double negative (DN) populations revealed a significant reduction in the DN1 population, in both the numbers of CD117(+) DN1 cells (the early thymocyte progenitors) and the CD117(-) DN1 cells in the thymus of CD45(-/-) mice. There was also a reduced frequency of CCR9(+) Lin(-)Sca-1(+)c-Kit(+) cells and common lymphoid progenitors in the CD45(-/-) bone marrow. Competitive bone marrow reconstitution showed a reduced contribution of DN1 cells from CD45(-/-) cells, consistent with an intrinsic defect in these cells. CD45(-/-) DN1 cells exhibited reduced proliferation in vivo and reduced CXCL12-mediated migration in vitro. The loss of CD45 led to the accumulation of an intermediate DN1.5 thymocyte population in vivo that was dependent on Notch for progression. In vivo, CD117(-) DN1 cells gave rise to gammadelta T cells. In vitro, CD117(-) DN1 cells progressed to DN4 on OP9-DL1 cells but CD117(-) DN1 cells lacking CD45 did not. CD45(-/-) CD117(-) DN1 cells were also deficient in TCRbeta expression. Thus, CD45 deficiency affects the development and progression of DN1 thymocytes.