In diffuse large B-cell lymphoma (DLBCL), the number of circulating monocytes and neutrophils represents an independent prognostic factor. These cell subsets include monocytic and granulocytic myeloid-derived suppressor cells (M- and G-MDSCs) defined by their ability to suppress T-cell responses. MDSCs are a heterogeneous population described in inflammatory and infectious diseases and in numerous tumors including multiple myeloma, chronic lymphocytic leukemia, and DLBCL. However, their mechanisms of action remain unclear. We broadly assessed the presence and mechanisms of suppression of MDSC subsets in DLBCL. First, a myeloid suppressive signature was identified by gene expression profiling in DLBCL peripheral blood. Accordingly, we identified, in a cohort of 66 DLBCL patients, an increase in circulating G-MDSC (Lin(neg)HLA-DR(neg)CD33(pos)CD11b(pos)) and M-MDSC (CD14(pos)HLA-DR(low)) counts. Interestingly, only M-MDSC number was correlated with the International Prognostic Index, event-free survival, and number of circulating Tregs. Furthermore, T-cell proliferation was restored after monocyte depletion. Myeloid-dependent T-cell suppression was attributed to a release of interleukin-10 and S100A12 and increased PD-L1 expression. In summary, we identified expanded MDSC subsets in DLBCL, as well as new mechanisms of immunosuppression in DLBCL.

Accumulating evidences indicate that the cellular and molecular microenvironment of follicular lymphoma (FL) has a key role in both lymphomagenesis and patient outcome. Malignant FL B cells are found admixed to specific stromal and immune cell subsets, in particular CD4 pos T cells displaying phenotypic features of follicular helper T cells (T FH ). The goal of our study was to functionally characterize intratumoral CD4 pos T cells. We showed that CXCR5 hi ICOS hi CD4 pos T cells sorted from FL biopsies comprise at least two separate cell populations with distinct genetic and functional features: (i) CD25 pos follicular regulatory T cells (T FR ), and (ii) CD25 neg T FH displaying a FL-B cell supportive activity without regulatory functions. Furthermore, despite their strong similarities with tonsil-derived T FH , purified FL-derived T FH displayed a specific gene expression profile including an overexpression of several genes potentially involved directly or indirectly in lymphomagenesis, in particular TNF, LTA, IL4 or CD40LG. Interestingly, we further demonstrated that these two last signals efficiently rescued malignant B cells from spontaneous and rituximab-induced apoptosis. Altogether, our study demonstrates that tumor-infiltrating CD4 pos T cells are more heterogeneous than previously presumed, and underlines for the first time the crucial role of T FH in the complex set of cellular interactions within FL microenvironment.

Interleukin-15 (IL-15) has been extensively studied for its role in the survival and proliferation of NK and T cells through a unique mechanism of trans-presentation by producer cells. Conversely, whereas activated B cells have been described as IL-15-responding cells, the cellular and molecular context sustaining this effect remains unexplored. In this study, we found that, whereas human B cells could not respond to soluble IL-15, monocytes and lymphoid tissue-derived macrophages but not stromal cells efficiently trans-present IL-15 to normal B cells and cooperate with T-cell-derived CD40L to promote IL-15-dependent B-cell proliferation. Furthermore, CD40L signaling triggers a Src-independent upregulation of STAT5 expression and favors a Src-dependent phosphorylation of STAT5 in response to IL-15. In follicular lymphoma (FL), immunohistochemical studies reported a strong relationship between malignant B cells, infiltrating macrophages and T cells. We show here an overexpression of IL-15 in purified tumor-associated macrophages, and STAT5A in purified tumor B cells. Moreover, FL B cells respond to IL-15 trans-presented by monocytes/macrophages, in particular, in the presence of CD40L-mediated signaling. This cooperation between IL-15 and CD40L reinforces the importance of tumor microenvironment and unravels a mechanism of FL growth that should be considered if using IL-15 as a drug in this disease.

Drug monitoring of TAC intracellular concentrations and determination of the calcineurin activity are among future potential biomarkers of acute rejection in transplant recipients. A better knowledge of the relationship between TAC whole blood and intracellular concentrations and calcineurin activity appears necessary before planning clinical trials to evaluate their potential interest as predictive biomarkers.

In follicular lymphoma (FL), follicular helper T cells (TFH) have been depicted as one of the main components of the malignant B-cell niche and a promising therapeutic target. Although defined by their capacity to sustain FL B-cell growth together with specific gene expression and cytokine secretion profiles, FL-TFH constitute a heterogeneous cell population. However, specific markers reflecting such functional heterogeneity are still lacking. In this study, we demonstrate that CD10 identifies a subset of fully functional germinal center TFH in normal secondary lymphoid organs. Importantly, this subset is amplified in the FL context, unlike in other B-cell lymphomas with a follicular growth pattern. Furthermore, whereas FL-TFH produce high levels of interleukin (IL)-21 and low levels of IL-17 irrespectively of their CD10 expression, CD10(pos) FL-TFH specifically exhibit an IL-4(hi)IFN-γ(lo)TNF-α(hi) cytokine profile associated with a high capacity to sustain directly and indirectly malignant B-cell survival. Altogether, our results highlight the important role of this novel functional subset in the FL cell niche.

Background: The Kleihauer-Betke test (KBT) is the most widely used assay for fetomaternal hemorrhage (FMH) detection in rhesus D negative women. In the current study, we sought to evaluate the performance of a flow cytometry (FCM) kit (FMH QuikQuant) using an anti-HbF antibody.Methods: Eighty-three pregnant women, 58 umbilical cord blood (UCB) dilutions in adult blood, and 6 control samples were tested in parallel with FCM and KBT.Results

Purpose: Follicular lymphoma arises from a germinal center B-cell proliferation supported by a bidirectional crosstalk with tumor microenvironment, in particular with follicular helper T cells (Tfh). We explored the relation that exists between the differentiation arrest of follicular lymphoma cells and loss-of-function of CREBBP acetyltransferase. Experimental Design: The study used human primary cells obtained from either follicular lymphoma tumors characterized for somatic mutations, or inflamed tonsils for normal germinal center B cells. Transcriptome and functional analyses were done to decipher the Band T-cell crosstalk. Responses were assessed by flow cytometry and molecular biology including ChIP-qPCR approaches. Results: Conversely to normal B cells, follicular lymphoma cells are unable to upregulate the transcription repressor, PRDM1, required for plasma cell differentiation. This defect occurs although the follicular lymphoma microenvironment is enriched in the potent inducer of PRDM1 and IL21, highly produced by Tfhs. In follicular lymphoma carrying CREBBP loss-of-function mutations, we found a lack of IL21-mediated PRDM1 response associated with an abnormal increased enrichment of the BCL6 protein repressor in PRDM1 gene. Moreover, in these follicular lymphoma cells, pan-HDAC inhibitor, vorinostat, restored their PRDM1 response to IL21 by lowering BCL6 bound to PRDM1. This finding was reinforced by our exploration of patients with follicular lymphoma treated with another pan-HDAC inhibitor. Patients showed an increase of plasma cell identity genes, mainly PRDM1 and XBP1, which underline the progression of follicular lymphoma B cells in the differentiation process. Conclusions: Our data uncover a new mechanism by which pan-HDAC inhibitors may act positively to treat patients with follicular lymphoma through the induction of the expression of plasma cell genes.

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