TREG and Tcon Dynamics after Allo-HSCT: Cgvhd Is Associated to Decreased NaïVe and Stem Cell Memory Subsets with a Concomitant Increase in Terminally Differentiated T Cell Subsets

Chronic Graft versus Host disease (cGVHD) is a major limiting factor for the success of allo-HSCT. In this prospective study we aimed to evaluate the association between the kinetics of Regulatory T cells (TREG) and Conventional CD4+T cells (TCON) reconstitution and the emergence of cGVHD. We performed a detailed phenotypic analysis by multiparametric flow cytometry using fresh blood from 39 patients undergoing unrelated donor HSCT after a reduced intensity conditioning regimen containing ATG over a 2 year period, representing a total of 213 samples analyzed. GVHD prophylaxis consisted of cyclosporine plus mycophenolate mofetil. 11 patients were excluded due to disease relapse and/or death due to infection or acute GVHD in the first 9 months post-HSCT. We observed indiscriminately low numbers of TREG (CD4+CD127lowFoxp3+CD25bright) until mo 6 after HSCT and reduced TREG numbers in patients developing cGVHD (GVHD+) versus those who did not (GVHD-) (p=0.02 at mo 9). We further studied the dynamics of TREG subset reconstitution. CM TREG (CD45RA-CD62L+) was the predominant population in both patient groups. EM (CD45RA-CD62L-) was the second most abundant TREG subset. CM and EM TREG numbers were similar between patient groups. EMRA (CD45RA+CD62L-) TREG remained very low throughout the follow-up but were significantly increased at mo 9 in GVHD+ (p= 0.03). Interestingly, Naïve TREG (CD45RA+CD62L+CD95-) started to emerge at mo 9 and were significantly reduced in GVHD+ patients at mo 12 (0.71 vs 0.14 cells/µl; p=0.02) The Stem Cell Memory subset (SCM), identified as CD45RA+CD62L+CD95+, is thought to be self renewing and multipotent, being able to differentiate into CM, EM and TEMRA memory subsets. While in GVHD- SCM TREG started to emerge at mo 9, this subset remained low in GVHD+. Statistically significant differences were observed at mo 18 (0.91 vs 0.15 cells/µl; p=0.02). To ascertain the role of thymic output in TREG reconstitution we quantified CD31+ naïve TREG. Recent Thymic Emigrant cells (RTE) TREG were significantly reduced in GVHD+ at mo 12 (0.8 vs 0.16cells/µl; p=0.02) and at mo 18 (1.93 vs 0.28 cells/µl; p=0.02). In order to clarify whether both thymic output and peripheral expansion were contributing factors to decreased Naïve TREG, we quantified proliferation using Ki-67. TREG from GVHD+ patients proliferated less from months 2 to 18 reaching statistical significance at mo 9 and 12 (p= 0.003 and 0.02, respectively), suggesting that decreased TREG numbers are at least partly due to reduced peripheral expansion. Taken together, these observations suggest a compromised peripheral expansion and de novo generation of TREG through thymic output in cGVHD patients. Of note, susceptibility to apoptosis was not increased in TREG from GVHD+ patients, as Bcl-2 levels tended to be higher in relation to GVHD- patients. In the CD4+Foxp3- TCON population, we observed a clear predominance of EM in all patients. These cells, together with CM, are the first to appear at similar levels in both patient groups. EMRA emerged at higher numbers in GVHD+, although the results did not reach statistical significance. Naïve and RTE TCON started to emerge after mo 6 in GVHD-. Interestingly, these cells remained much lower in GVHD+ vs GVHD- patients throughout the follow-up, reaching statistical significance at mo 12 (p=0.03 for naïve; p=0.03 for RTE TCON). SCM TCON remained very low in all patients showing a tendency to be reduced in GVHD+ when compared to GVHD-. This difference reached statistical significance at mo 18 (6.85 vs 2.13 cells/µl; p=0.02). The small number of TREG and TCON subsets in GVHD+ patients were unlikely due to increased susceptibility to apoptosis, as assessed by Bcl-2 expression. The low numbers of cells within naïve and SCM TREG gates precluded the analysis of Bcl-2 expression in these subsets. Bcl-2 tended to be increased in total TREG CM and EM in GVHD+. In TCONs, Bcl-2 levels were similar in both patient groups. In summary, our data in patients developing cGVHD suggest that decreased thymic output and increased differentiation into terminally differentiated effector cells may have a negative impact on the number of naïve and SCM TCON and TREG. We speculate that the inability to generate and maintain the more immature TREG subsets may lead to decreased TREG numbers after 6 months post transplant, potentially resulting in decreased control of effector T cells contributing to the development of cGVHD. Disclosures Ritz: Kiadis: Membership on an entity's Board of Directors or advisory committees.

Glioblastoma: Biology, Genetics, and Behavior

Overview: Glioblastoma (GBM) is a highly malignant, rapidly progressive astrocytoma that is distinguished pathologically from lower-grade tumors by necrosis and microvascular hyperplasia. The global pattern of growth changes dramatically with the development of GBM histology and is characterized by hypoxia-driven peripheral expansion from a growing necrotic core. Necrotic foci present centrally in GBM and are typically surrounded by “pseudopalisading” cells—a configuration that is relatively unique and long recognized as an ominous prognostic feature. Theses pseudopalisades are severely hypoxic, overexpress hypoxia inducible factor-1 (HIF-1), and secrete proangiogenic factors, such as vascular endothelial growth factor (VEGF) and interleukin 8 (IL-8). The microvascular hyperplasia that emerges in response promotes peripheral tumor expansion. Recent evidence suggests that pseudopalisades represent a wave of tumor cells actively migrating away from central hypoxia that arises following a vascular insult. Vaso-occlusive and prothrombotic mechanisms in GBM could readily explain the presence of pseudopalisading necrosis in tissue sections, the rapid peripheral expansion on neuroimaging, and the dramatic shift to an accelerated rate of clinical progression as a result of hypoxia-induced angiogenesis. The genetic alterations that coincide with progression to GBM include amplification of epidermal growth factor receptor (EGFR), deletion of CDKN2A, and mutation or deletion of PTEN. Other diagnostic and prognostic tests used in neuro-oncology include assessment of 1p/19q, MGMT promoter methylation, IDH1, and p53. More recently, the Cancer Genome Atlas data have indicated that there are four robust transcriptional classes of GBM, referred to as proneural, neural, classical, and mesenchymal. These classes have genetic associations and may pave the road for future development of targeted therapies.

Keratoacanthoma Centrifugum Marginatum with Atypical Scar

Keratoacanthoma centrifugum marginatum (KCM) is a rare variant of keratoacanthoma (KA). It is characterized by a progressive peripheral expansion and central healing leaving atrophic scar. It is sometimes confused with squamous cell carcinoma (SCC) both clinically and histopathologically. We here report a case of KCM over the extensor aspect of the right forearm in a 57-year-old man with an abnormal looking scar.

Left-peripheral expansion of the English NP

This article is concerned with peripheral modifiers in the English noun phrase. It is argued that this kind of modification is an Early Modern English innovation. Later, in the nineteenth century, the slot underwent a rapid extension on both the type and the token levels, as is shown by historical corpus inquiry. To account for the diachronic processes involved, a constructional, usage-based approach is used, with an onomasiological rather than a semasiological perspective on grammaticalisation.

Interleukin-7 Produced by Antigen Presenting Cells Regulates the Homeostatic Peripheral Expansion of Naive CD4 T Cells.

Interleukin-7 (IL-7) is the only cytokine demonstrated thus far to directly support the development and maintenance of naive T cells. Interleukin-7 is produced mainly by the stroma of lymphoid organs but also to a lesser extent by antigen presenting cells. Dynamic changes in the relative availability of IL-7 during lymphopenia support T cell homeostatic peripheral expansion (HPE). Whereas HPE is very efficient at reconstituting the pool of mature CD8 T lymphocytes, regeneration of CD4 T lymphocytes via HPE is more problematic and deficits in CD4 T lymphocytes persist for years in humans following lymphodepletion. We demonstrate that in mice, CD4+ T cells undergo substantially diminished HPE compared to CD8+ T cells during lymphopenia. We hypothesized that CD4+ T cells uniquely require both MHC Class II plus IL-7 for survival and expansion during lymphopenia and that the availability of these signals are limited by the availability of IL-7 producing APCs. Consistent with this hypothesis, studies performed in chimeric mice showed that cells derived from APCs, but not stromal cells, provided the endogenous IL-7 that is require for naive CD4+ T cell HPE. Furthermore, whereas systemic exposure to high levels of rhIL-7 did not induce efficient homeostatic peripheral expansion of CD4+ cells, in vivo modulation of Class II expressing cells by flt3 ligand promoted homeostatic expansion of CD4+ T cells. Surprisingly however, we found that APCs respond to elevated systemic IL-7 by diminishing production of IL-7, a loop mediated by IL-7Rα and Stat5. As a result, elevated systemic IL-7 levels present during lymphopenia paradoxically diminish the production of IL-7 by APCs and thereby diminish CD4 HPE. This was directly demonstrated by experiments wherein CD4+ HPE was dramatically augmented in chimeric mice generated such that bone marrow derived cells lacked IL7Rα or Stat5. This work demonstrates a critical role for APC derived IL-7 in CD4+ regeneration and provides a new paradigm for understanding why prolonged CD4+ lymphopenia occurs following T cell depletion in humans.