Supplementary Materials1. in FL and correlated with substandard patient outcomes. models revealed that CD70+ lymphoma cells played an important role in expanding this population. Taken together, our mass cytometry results identified CD4+ memory T cell populations that are poorly functional due to loss of co-stimulatory receptor expression and are associated with an inferior survival in FL. In Brief Yang et al. utilize mass cytometry (CyTOF) to characterize intratumoral T cells and explore the clinical relevance of T cell subsets in follicular lymphoma (FL). Clustering analysis reveals an immune signature with reduced expression of co-stimulatory molecules on intratumoral T cells that correlated with a poor prognosis in FL. Graphical Abstract Open in a separate window INTRODUCTION The tumor microenvironment plays a critical role in the regulation of antitumor immunity, thereby impacting patient end result in follicular lymphoma (Alvaro et al., 2006; Dave et al., 2004; Glas et al., 2007). Previous studies have recognized T cell subsets with unique functional properties, such as TH1, TH2, TH17, TH22, and Treg (Duhen et al., 2009; Harrington et al., 2005; Nograles et al., 2009; Park et al., 2005). In addition to these canonical T cell subsets, specific T cell subsets have recently been shown to play crucial functions in immunogenic dysregulation characteristic of certain disease states, such as cancer. For example, in B cell non-Hodgkin lymphoma, our group has identified involvement of TIM-3+ (Yang et al., 2012) and LAG-3+ (Yang et al., 2017) T cells in cytokine-induced T cell exhaustion and have demonstrated a role for CD70+ T cells in transforming growth factor (TGF-)-mediated T cell inhibition (Yang et al., 2014) within the tumor microenvironment. Follicular lymphoma (FL) is an indolent B cell malignancy characterized by an extensive but poorly functional T cell infiltrate in the tumor microenvironment. Chemoimmunotherapy is effective in treating FL and rituximab, an anti-CD20 antibody (Ab), combined with chemotherapy (including bendamustine or CHOP) has significantly improved outcomes for FL patients. Selumetinib manufacturer However, even though Selumetinib manufacturer median 5-12 months overall survival reached 74% in FL patients treated with chemoimmunotherapy, a subset of patients who progress early have a very poor end result (Maurer et al., 2016). Previous studies have found that an impaired immune response to malignant lymphoma cells accounts in part for the poor outcome in this subset of patients (Dave et al., 2004). In FL, increased numbers of intratumoral T cells overall is an immune signature that correlates with the favorable end result (Dave et al., 2004; Wahlin et al., 2007). However, the prognostic significance of intratumoral T cells is usually controversial in that T cell subsets may either positively or negatively correlate with patient end result (Laurent et al., 2011; Lee et al., 2006; Wahlin et al., 2010). The prognostic impact of T cells overall may also be influenced by the treatment given. Therefore, the question occurs whether a specific T cell signature predominantly predicts patient end result in FL. In FL, the canonical T cell subsets only account for a portion of intratumoral T cells, and the phenotype of many intratumoral T cells is not well described. In addition, the effect of malignant cells on functional characteristics of known T cell subsets, such as worn out T cells, T helper cells, and senescent T cells, has not been extensively analyzed, in CDKN2B part due to limitations in traditional methodologies. The emergence of mass cytometry or CyTOF (cytometry by Selumetinib manufacturer time of airline flight) has revolutionized single-cell proteomics, enabling a comprehensive understanding of cell phenotype, signaling pathways, and function (Amir et al., 2013; Bendall et al., 2011; Wang et al., 2012). CyTOF offers huge advantages over the conventional flow cytometer by providing 135 detection channels and the ability to measure more than 40 markers per cell. CyTOF has been used to characterize the B cell infiltrate in FL patients (Wogsland et al., 2017), but the T cell subsets in FL have not been comprehensively defined. In Selumetinib manufacturer the present study, we employed CyTOF with a broad range of surface markers to characterize intratumoral T cells from a cohort of FL specimens and from Selumetinib manufacturer non-malignant tissues that served as controls. We extracted.