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Regulatory T cells (Tregs) are often enriched in tumors, where their immunosuppressive function has a key role in tumor persistence and progression. In colorectal cancer (CRC), however, Tregs are frequently associated with an improved clinical outcome. Tumor-infiltrating Tregs have been shown to exhibit a distinct signature comprising the co-stimulatory molecules (OX40, 4-1BB), cytokine receptors (IL1R2, IL21R, CCR8, CD30), and co-inhibitory molecules (PD-L1, TIGIT). Here, we showed by flow cytometry that circulating CD45RO+ Tregs from patients with CRC (n = 25) have elevated CD30 and OX40 expression compared to healthy subjects (n = 14). We identified co-expression of CD30 and OX40 on circulating CD45RO+ Tregs using single-cell images captured by the DEPArray™ system. The frequency of CD30+OX40+CD45RO+ Tregs was significantly higher in CRC patients than in healthy subjects (P +OX40+ Treg subset could strongly discriminate between CRC patients and healthy subjects with the highest accuracy of 92.3%, an AUC of 0.92, a sensitivity of 88%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 82.35%, and a trade-off value of 3.44%, compared to other Treg subsets. Consistently, multiplex-IHC/IF of tumor-infiltrating Tregs revealed a significant association between high densities of CD30+OX40+ Tregs and improved overall survival; no such association was found for other subsets. These data suggest a potential role for CD30+OX40+ Tregs as a diagnostic or prognostic biomarker in CRC.

The intestinal immune system can respond to invading pathogens yet maintain immune tolerance to self-antigens and microbiota. Myeloid cells are central to these processes, but the signaling pathways that underlie tolerance versus inflammation are unclear. Here we show that mice lacking Calcineurin B in CD11chighMHCII+ cells (Cnb1 CD11c mice) spontaneously develop intestinal inflammation and are susceptible to induced colitis. In these mice, colitis is associated with expansion of T helper type 1 (Th1) and Th17 cell populations and a decrease in the number of FoxP3+ regulatory T (Treg) cells, and the pathology is linked to the inability of intestinal Cnb1-deficient CD11chighMHCII+ cells to express IL-2. Deleting IL-2 in CD11chighMHCII+ cells induces spontaneous colitis resembling human inflammatory bowel disease. Our findings identify that the calcineurin–NFAT–IL-2 pathway in myeloid cells is a critical regulator of intestinal homeostasis by influencing the balance of inflammatory and regulatory responses in the mouse intestine.

CD38 is involved in the adenosine pathway, which represents one of the immunosuppressive mechanisms in cancer. CD38 is broadly expressed across immune cell subsets, including human macrophages differentiated in vitro from monocytes, but expression by tissue-resident macrophages remains to be demonstrated. We analysed tissue samples obtained from 66 patients with hepatocellular carcinoma (HCC) from Singapore and analysed using immunohistochemistry. Tumor-infiltrating leukocytes (TILs) were further examined using DEPArrayTM., and the phenotype of freshly isolated TILs was determined using flow cytometry. It is found that CD38 was frequently co-expressed with the macrophage-specific marker CD68. CD38+CD68+ macrophage density was associated with improved prognosis after surgery, while total CD68+ macrophage density was associated with poor prognosis. DEPArrayTM. analysis revealed the presence of large (>10 µm), irregularly shaped CD45+CD14+ cells that resembled macrophages, with concurrent CD38+ expression. Flow cytometry also revealed that majority of CD14+HLA-DR+ cells expressed CD38. In conclusion, CD38 expression was clearly demonstrated on human macrophages in an in vivo setting. The positive association identified between CD38+ macrophage density and prognosis may have implications for routine diagnostic work.

TO THE EDITOR: Vitreoretinal lymphoma (VRL) is a rare ocular malignancy that occurs as a primary intraocular lymphoma or secondary manifestation of primary central nervous system lymphoma (PCNSL).[1][1] Although the diagnosis is classically made by cytologic and immunohistochemical confirmation of

Functional T-cell responses are initiated by physical interactions between T-cells and antigen-presenting cells (APCs), including dendritic cells (DCs) and B-cells. T-cells are activated more effectively by DCs than by B-cells, but little is known about the key molecular mechanisms that underpin the particular potency of DC in triggering T-cell responses. To better understand the influence of physical intercellular interactions on APC efficacy in activating T-cells, we used single cell force spectroscopy to characterize and compare the mechanical forces of interactions between DC:T-cells and B:T-cells. Following antigen stimulation, intercellular interactions of DC:T-cell conjugates were stronger than B:T-cell interactions. DCs induced higher levels of T-cell calcium mobilization and production of IL-2 and IFNγ than were elicited by B-cells, thus suggesting that tight intercellular contacts are important in providing mechanically stable environment to initiate T-cell activation. Blocking antibodies targeting surface co-stimulatory molecules CD80 or CD86 weakened intercellular interactions and dampen T-cell activation, highlighting the amplificatory roles of CD80/86 in regulating APC:T-cell interactions and T-cell functional activation. The variable strength of mechanical forces between DC:T-cells and B:T-cell interactions were not solely dependent on differential APC expression of CD80/86, since DCs were superior to B-cells in promoting strong interactions with T-cells even when CD80 and CD86 were inhibited. These data provide mechanical insights into the effects of co-stimulatory molecules in regulating APC:T-cell interactions.

Ag recognition is achieved through the communication across intercellular contacts between T cells and APCs such as dendritic cells (DC). Despite remarkable progress in delineating detailed molecular components at the intercellular contacts, little is known about the functional roles of physical cross-junctional adhesion between T and DC in shaping T cell responses. In addition, the mechanisms underlying sensitivity and specificity of Ag discrimination by T cells at intercellular contacts remain to be elucidated. In this study, we use single-cell force spectroscopy to probe the mechanical interactions between DC and T cells in response to stimulation with a panel of altered peptide ligands. The results show that intercellular interactions of DC–T cell conjugates exhibited different ranges of interaction forces in peptide-dependent manners that match the ability of the peptides to activate T cells. Elevated calcium mobilization and IL-2 secretion by T cells were only promoted in response to antigenic peptides that induce strong interaction forces, suggesting that mechanically stable DC–T cell contacts are crucial for driving T cell activation. Strong interactions were not solely dependent on cell-surface molecules such as TCRs and the adhesion molecule LFA-1, but were also controlled by cytoskeletal dynamics and the integrity of membrane lipid rafts. These data provide novel mechanical insights into the effect of Ag affinity on intercellular contacts that align with T cell responsiveness.

Programmed death one (PD-1) is a well-established co-inhibitory regulator that suppresses proliferation and cytokine production of T cells. Despite remarkable progress in delineating the functional roles of PD-1 on T lymphocytes, little is known about the regulatory role of PD-1 expressed on myeloid cells such as dendritic cells (DCs). Here, we show that CD8+ T cells can be more potently activated to secrete IL-2 and IFNγ by PD-1-deficient DCs compared to wild-type DCs. Adoptive transfer of PD-1-deficient DCs demonstrated their superior capabilities in inducing antigen-specific CD8+ T cell proliferation in vivo. In addition, we provide first evidence demonstrating the existence of peripheral blood DCs and CD11c+ tumor-infiltrating myeloid cells that co-express PD-1 in patients with hepatocellular carcinoma (HCC). The existence of PD-1-expressing HCC-infiltrating DCs (HIDCs) was further supported in a mouse model of HCC. Intratumoral transfer of PD-1-deficient DCs rendered recipient mice resistant to the growth of HCC by promoting tumor-infiltrating CD8+ effector T cells to secrete perforin and granzyme B. This novel finding provides a deeper understanding of the role of PD-1 in immune regulation and has significant implications for cancer immunotherapies targeting PD-1.

Antigen recognition and discrimination by T lymphocyte are essential in initiating appropriate immune responses. The mechanisms underlying exquisite sensitivity and specificity of antigen discrimination are not fully elucidated but involved physical intercellular interactions between T cell and antigen-presenting cell (APC) including dendritic cells (DCs) and B cells. Using single cell force spectroscopy (SCFS), we have successfully probe mechanical interactions between DC and T cells in response to a panel of altered peptide ligands (APLs). In the presence of different type of APLs, DC:T conjugate displays different ranges of mechanical forces that match their corresponding T cell responsiveness. Strong cell-cell interaction forces are contributed not only by surface adhesion molecules including TCR:pMHC, CD28:B7 and ICAM-1:LFA-1 interaction pairs, but also dependent on the integrity of membrane cholesterol and cytoskeleton dynamics. As compared to B:T interactions, stronger DC:T cell-cell interactions are likely to provide a mechanically stable environment that induces potent functional T cell activation, suggesting that the measurement of mechanical forces could be a significant predictor of T cell functional activation efficacy. Our SCFS studies provide mechanical insights into the adhesive roles of cell surface proteins in regulating APC:T cell-cell interactions. Functional roles of TLR ligands in regulating APC:T interactions and T-cell responses will be discussed.