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T cells infiltrating follicular lymphoma (FL) tumors are considered dysfunctional, yet the optimal target for immune checkpoint blockade is unknown. Characterizing coinhibitory receptor expression patterns and signaling responses in FL T-cell subsets might reveal new therapeutic targets. Surface expression of 9 coinhibitory receptors governing T-cell function was characterized in T-cell subsets from FL lymph node tumors and from healthy donor tonsils and peripheral blood samples, using high-dimensional flow cytometry. The results were integrated with T-cell receptor (TCR)-induced signaling and cytokine production. Expression of T-cell immunoglobulin and ITIM domain (TIGIT) ligands was detected by immunohistochemistry. TIGIT was a frequently expressed coinhibitory receptor in FL, expressed by the majority of CD8 T effector memory cells, which commonly coexpressed exhaustion markers such as PD-1 and CD244. CD8 FL T cells demonstrated highly reduced TCR-induced phosphorylation (p) of ERK and reduced production of IFNγ, while TCR proximal signaling (p-CD3ζ, p-SLP76) was not affected. The TIGIT ligands CD112 and CD155 were expressed by follicular dendritic cells in the tumor microenvironment. Dysfunctional TCR signaling correlated with TIGIT expression in FL CD8 T cells and could be fully restored upon culture. The costimulatory receptor CD226 was downregulated in TIGIT compared with TIGIT CD8 FL T cells, further skewing the balance toward immunosuppression. TIGIT blockade is a relevant strategy for improved immunotherapy in FL. A deeper understanding of the interplay between coinhibitory receptors and key T-cell signaling events can further assist in engineering immunotherapeutic regimens to improve clinical outcomes of cancer patients. .
©2017 American Association for Cancer Research.

It has been proposed that CD6, an important regulator of T cells, functions by interacting with its currently identified ligand, CD166, but studies performed during the treatment of autoimmune conditions suggest that the CD6-CD166 interaction might not account for important functions of CD6 in autoimmune diseases. The antigen recognized by mAb 3A11 has been proposed as a new CD6 ligand distinct from CD166, yet the identity of it is hitherto unknown. We have identified this CD6 ligand as CD318, a cell surface protein previously found to be present on various epithelial cells and many tumor cells. We found that, like CD6 knockout (KO) mice, CD318 KO mice are also protected in experimental autoimmune encephalomyelitis. In humans, we found that CD318 is highly expressed in synovial tissues and participates in CD6-dependent adhesion of T cells to synovial fibroblasts. In addition, soluble CD318 is chemoattractive to T cells and levels of soluble CD318 are selectively and significantly elevated in the synovial fluid from patients with rheumatoid arthritis and juvenile inflammatory arthritis. These results establish CD318 as a ligand of CD6 and a potential target for the diagnosis and treatment of autoimmune diseases such as multiple sclerosis and inflammatory arthritis.

IL-15 is currently undergoing clinical trials to assess its efficacy for treatment of advanced cancers. The combination of IL-15 with soluble IL-15Rα generates a complex termed IL-15 superagonist (IL-15 SA) that possesses greater biological activity than IL-15 alone. IL-15 SA is considered an attractive antitumor and antiviral agent because of its ability to selectively expand NK and memory CD8(+) T (mCD8(+) T) lymphocytes. However, the adverse consequences of IL-15 SA treatment have not been defined. In this study, the effect of IL-15 SA on physiologic and immunologic functions of mice was evaluated. IL-15 SA caused dose- and time-dependent hypothermia, weight loss, liver injury, and mortality. NK (especially the proinflammatory NK subset), NKT, and mCD8(+) T cells were preferentially expanded in spleen and liver upon IL-15 SA treatment. IL-15 SA caused NK cell activation as indicated by increased CD69 expression and IFN-γ, perforin, and granzyme B production, whereas NKT and mCD8(+) T cells showed minimal, if any, activation. Cell depletion and adoptive transfer studies showed that the systemic toxicity of IL-15 SA was mediated by hyperproliferation of activated NK cells. Production of the proinflammatory cytokine IFN-γ, but not TNF-α or perforin, was essential to IL-15 SA-induced immunotoxicity. The toxicity and immunological alterations shown in this study are comparable to those reported in recent clinical trials of IL-15 in patients with refractory cancers and advance current knowledge by providing mechanistic insights into IL-15 SA-mediated immunotoxicity.
Copyright © 2015 by The American Association of Immunologists, Inc.

BACKGROUND - IL-1 receptor-associated kinase 4 (IRAK-4) is an effector of the Toll-like receptor and IL-1 receptor pathways that plays a critical role in innate immune responses. The role of IRAK-4 in adaptive immune functions in human subjects is incompletely understood.
OBJECTIVE - We sought to evaluate T-cell function in IRAK-4 deficient patients.
METHODS - We compared upregulation of CD25 and CD69 on T cells and production of IL-2, IL-6, and IFN-gamma after stimulation of PBMCs from 4 IRAK-4-deficient patients and healthy control subjects with anti-CD3 and anti-CD28.
RESULTS - Upregulation of CD25 and CD69 on T cells and production of IL-6 and IFN-gamma, but not IL-2, was significantly reduced in IRAK-4-deficient patients.
CONCLUSIONS - IRAK-4-deficient patients have defects in T-cell activation.
Copyright 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

Regulatory T cells (Tregs) are a suppressive subset of CD4(+) T lymphocytes implicated in the prevention of acute GVHD (aGVHD) after allo-SCT (ASCT). To determine whether increased frequency of Tregs with a skin-homing (cutaneous lymphocyte Ag, CLA(+)) or a gut-homing (α(4)β(7)(+)) phenotype is associated with reduced risk of skin or gut aGVHD, respectively, we quantified circulating CLA(+) or α(4)β(7)(+) on Tregs at the time of neutrophil engraftment in 43 patients undergoing ASCT. Increased CLA(+) Tregs at engraftment was associated with the prevention of skin aGVHD (2.6 vs 1.7%; P=0.038 (no skin aGVHD vs skin aGVHD)), and increased frequencies of CLA(+) and α(4)β(7)(+) Tregs were negatively correlated with severity of skin aGVHD (odds ratio (OR), 0.67; 95% confidence interval (CI), 0.46-0.98; P=0.041) or gut aGVHD (OR, 0.93; 95% CI, 0.88-0.99; P=0.031), respectively. This initial report suggests that Treg tissue-homing subsets help to regulate organ-specific risk and severity of aGVHD after human ASCT. These results need to be validated in a larger, multicenter cohort.

Macrophage migration inhibitory factor (MIF) plays an important role in inflammatory diseases. It has been reported that anti-MIF treatment and mif-gene disruption ameliorate joint inflammation in a mouse model of arthritis induced by anti-type II collagen monoclonal antibodies and lipopolysaccharide (anti-IIC mAb/LPS). In the present study, using the anti-IIC mAb/LPS system, we have analyzed arthritis in MIF-transgenic (MIFTg) and wild-type C57BL/6 (WT) mice. We found that MIFTg mice developed more severe arthritis than WT mice. The histopathological scores were significantly higher in MIFTg mice and significantly increased numbers of CD69+ T cells were detected in the spleens of these arthritic MIFTg mice, compared with WT mice. Natural killer T (NKT) cells from MIFTg mice, compared with WT mice, produced reduced amounts of IL-4 upon stimulation with agr;-galactosylceramide (alpha-GalCer). Further, repeated administration of alpha-GalCer to MIFTg mice resulted in a profound reduction of both clinical and histopathological scores of arthritis, with a significant decrease in IL-6. The present findings demonstrate that overexpression of MIF exacerbates inflammation in this arthritis model and that NKT cells play an ameliorating role upon stimulation with alpha-GalCer in the inflammatory process in MIFTg mice.

The type II transmembrane protein CD98, best known as the heavy chain of the heterodimeric amino acid transporters (HAT), is required for the surface expression and basolateral localization of this transporter complex in polarized epithelial cells. CD98 also interacts with beta1 integrins resulting in an increase in their affinity for ligand. In this study we explored the role of the transmembrane and cytoplasmic domains of CD98 on integrin-dependent cell adhesion and migration in polarized renal epithelial cells. We demonstrate that the transmembrane domain of CD98 was sufficient, whereas the five N-terminal amino acids of this domain were required for CD98 interactions with beta1 integrins. Overexpression of either full-length CD98 or CD98 lacking its cytoplasmic tail increased cell adhesion and migration, whereas deletion of the five N-terminal amino acids of the transmembrane domain of CD98 abrogated this effect. CD98 and mutants that interacted with beta1 integrins increased both focal adhesion formation and FAK and AKT phosphorylation. CD98-induced cell adhesion and migration was inhibited by addition of phosphoinositol 3-OH kinase (PI3-K) inhibitors suggesting these cell functions are PI3-K-dependent. Finally, CD98 and mutants that interacted with beta1, induced marked changes in polarized renal epithelial cell branching morphogenesis in collagen gels. Thus, in polarized renal epithelial cells, CD98 might be viewed as a scaffolding protein that interacts with basolaterally expressed amino acid transporters and beta1 integrins and can alter diverse cellular functions such as amino acid transport as well as cell adhesion, migration and branching morphogenesis.

CD98hc (SLC3A2) constitutively and specifically associates with beta(1) integrins and is highly expressed on the surface of human tumor cells irrespective of the tissue of origin. We have found here that expression of CD98hc promotes both anchorage- and serum-independent growth. This oncogenic activity is dependent on beta(1) integrin-mediated phosphoinositol 3-hydroxykinase stimulation and the level of surface expression of CD98hc. Using chimeras of CD98hc and the type II membrane protein CD69, we show that the transmembrane domain of CD98hc is necessary and sufficient for integrin association in cells. Furthermore, CD98hc/beta(1) integrin association is required for focal adhesion kinase-dependent phosphoinositol 3-hydroxykinase activation and cellular transformation. Amino acids 82-87 in the putative cytoplasmic/transmembrane region appear to be critical for the oncogenic potential of CD98hc and provide a novel mechanism for tumor promotion by integrins. These results explain how high expression of CD98hc in human cancers contributes to transformation; furthermore, the transmembrane association of CD98hc and beta(1) integrins may provide a new target for cancer therapy.

In vivo administration of NKT cell ligand, alpha-galactosylceramide (alpha-GalCer), caused the activation of NKT cells to induce a strong NK activity and cytokine production by CD1d-restricted mechanisms. Surprisingly, we also found that alpha-GalCer induced the activation of immunoregulatory cells involved in acquired immunity. Specifically, in vivo administration of alpha-GalCer resulted in the induction of the early activation marker CD69 on CD4(+) T cells, CD8(+) T cells and B cells in addition to macrophages and NKT cells. However, no significant induction of CD69 was observed on cells from CD1d- or V(alpha)14 NKT-deficient mice, indicating an essential role for the interaction between NKT cells and CD1d-expressing dendritic cells (DC) in the activation of acquired immunity in response to alpha-GalCer. Indeed, in vivo injection of alpha-GalCer resulted not only in the activation of NKT cells but also in the generation of CD69(+)CD8(+) T cells possessing both cytotoxic T lymphocyte (CTL) activity and IFN-gamma-producing ability. Tumor-specific CTL generation was also accelerated by alpha-GalCer. The critical role of CD40-CD40 ligand (CD40L)-mediated NKT-DC interaction during the development of CD69(+)CD8(+) CTL by alpha-GalCer was demonstrated by blocking experiments using anti-CD40L mAb. These findings provide direct evidence for a critical role of CD1d-restricted NKT cells and DC in bridging innate and acquired immunity.

BACKGROUND - Interleukin-4 (IL-4) can enhance immune function within various leukocyte populations and mediate antitumor effects in mice. In vitro, IL-4 activation of human lymphocytes is enhanced by prior exposure to interleukin-2 (IL-2). This phase I trial of continuous intravenous infusion (CI i.v.) IL-4 was performed to determine its toxicity and biologic activity. IL-2 was administered prior to a second course of IL-4 in the same patients to determine whether IL-2 exposure can enhance IL-4 effects in vivo.
PATIENTS AND METHODS - Seventeen patients with non-hematologic malignancies were entered on this trial. Treatment consisted of 7 days of CI i.v. IL-4 followed by a 2 week period off therapy, then a 4 day course of CI i.v. IL-2 at 11.2 MIU/m2/day followed by 3 days rest, and then a second 7 day course of CI i.v. IL-4. IL-4 dose escalation included 40 micrograms/m2/day (6 pts.), 120 micrograms/m2/day (3 pts.), 360 micrograms/m2/day (5 pts.), and 600 micrograms/m2/day (3 pts.).
RESULTS - Dose limiting toxicity occurred at 600 micrograms/m2/day of IL-4; a dose at which 2 of 3 patients exhibited a vascular leak syndrome characterized by weight gain, peripheral edema, effusions, oliguria, and diffuse rash. Pretreatment with IL-2 did not significantly enhance IL-4 toxicity in the 40-360 micrograms dose range. IL-4 treatment was associated with a modest, but significant increase in peripheral eosinophil counts (p = 0.004), but no consistent change in lymphocyte phenotype or function. Patients treated at the higher dose of IL-4 (360 micrograms) administered following IL-2, exhibited a marked increase in peripheral eosinophils after IL-4 therapy (p = 0.007). Following the second course of IL-4, we observed increases in the percent CD56+ (NK/LAK marker) lymphocytes (mean increase = 6.8%), above levels induced by the preceding IL-2 treatment (p = 0.055). A single minor durable tumor response was seen in a patient with metastatic renal cancer.
CONCLUSIONS - IL-4 administered at 360 micrograms/m2/day CI i.v. over seven days is the maximum tolerated dose and is tolerable following a 4 day course of IL-2. IL-4 therapy alone is associated with a modest eosinophilia. In patients receiving IL-2 prior to IL-4, both circulating eosinophils and CD56+ cells increased above levels observed early after IL-2 treatment. Based upon these results, phase II trials of IL-4 in combination with IL-2 could be planned in 'IL-2 sensitive' malignancies.