Adhesion and costimulation of proliferative responses of human gamma delta T cells by interaction of VLA-4 and VLA-5 with fibronectin

Galectin-3 Released by Pancreatic Ductal Adenocarcinoma Suppresses γδ T Cell Proliferation but Not Their Cytotoxicity

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressive tumor microenvironment with a dense desmoplastic stroma. The expression of β-galactoside-binding protein galectin-3 is regarded as an intrinsic tumor escape mechanism for inhibition of tumor-infiltrating T cell function. In this study, we demonstrated that galectin-3 is expressed by PDAC and by γδ or αβ T cells but is only released in small amounts by either cell population. Interestingly, large amounts of galectin-3 were released during the co-culture of allogeneic in vitro expanded or allogeneic or autologous resting T cells with PDAC cells. By focusing on the co-culture of tumor cells and γδ T cells, we observed that knockdown of galectin-3 in tumor cells identified these cells as the source of secreted galectin-3. Galectin-3 released by tumor cells or addition of physiological concentrations of recombinant galectin-3 did neither further inhibit the impaired γδ T cell cytotoxicity against PDAC cells nor did it induce cell death of in vitro expanded γδ T cells. Initial proliferation of resting peripheral blood and tumor-infiltrating Vδ2-expressing γδ T cells was impaired by galectin-3 in a cell-cell-contact dependent manner. The interaction of galectin-3 with α3β1 integrin expressed by Vδ2 γδ T cells was involved in the inhibition of γδ T cell proliferation. The addition of bispecific antibodies targeting γδ T cells to PDAC cells enhanced their cytotoxic activity independent of the galectin-3 release. These results are of high relevance in the context of an in vivo application of bispecific antibodies which can enhance cytotoxic activity of γδ T cells against tumor cells but probably not their proliferation when galectin-3 is present. In contrast, adoptive transfer of in vitro expanded γδ T cells together with bispecific antibodies will enhance γδ T cell cytotoxicity and overcomes the immunosuppressive function of galectin-3.

Integral Roles for Integrins in γδ T Cell Function

Integrins are adhesion receptors on the cell surface that enable cells to respond to their environment. Most integrins are heterodimers, comprising α and β type I transmembrane glycoprotein chains with large extracellular domains and short cytoplasmic tails. Integrins deliver signals through multiprotein complexes at the cell surface, which interact with cytoskeletal and signaling proteins to influence gene expression, cell proliferation, morphology, and migration. Integrin expression on γδ T cells (γδTc) has not been systematically investigated; however, reports in the literature dating back to the early 1990s reveal an understated role for integrins in γδTc function. Over the years, integrins have been investigated on resting and/or activated peripheral blood-derived polyclonal γδTc, γδTc clones, as well as γδ T intraepithelial lymphocytes. Differences in integrin expression have been found between αβ T cells (αβTc) and γδTc, as well as between Vδ1 and Vδ2 γδTc. While most studies have focused on human γδTc, research has also been carried out in mouse and bovine models. Roles attributed to γδTc integrins include adhesion, signaling, activation, migration, tissue localization, tissue retention, cell spreading, cytokine secretion, tumor infiltration, and involvement in tumor cell killing. This review attempts to encompass all reports of integrins expressed on γδTc published prior to December 2017, highlights areas warranting further investigation, and discusses the relevance of integrin expression for γδTc function.

Rv2468c, a novel Mycobacterium tuberculosis protein that costimulates human CD4+ T cells through VLA-5

Mtb regulates many aspects of the host immune response, including CD4+ T lymphocyte responses that are essential for protective immunity to Mtb, and Mtb effects on the immune system are paradoxical, having the capacity to inhibit (immune evasion) and to activate (adjuvant effect) immune cells. Mtb regulates CD4+ T cells indirectly (e.g., by manipulation of APC function) and directly, via integrins and TLRs expressed on T cells. We now report that previously uncharacterized Mtb protein Rv2468c/MT2543 can directly regulate human CD4+ T cell activation by delivering costimulatory signals. When combined with TCR stimulation (e.g., anti-CD3), Rv2468c functioned as a direct costimulator for CD4+ T cells, inducing IFN-γ secretion and T cell proliferation. Studies with blocking antibodies and soluble RGD motifs demonstrated that Rv2468c engaged integrin VLA-5 (α5β1) on CD4+ T cells through its FN-like RGD motif. Costimulation by Rv2468c induced phosphorylation of FAKs and Pyk2. These results reveal that by expressing molecules that mimic host protein motifs, Mtb can directly engage receptors on CD4+ T cells and regulate their function. Rv2468c-induced costimulation of CD4+ T cells could have implications for TB immune pathogenesis and Mtb adjuvant effect.

Influence of T cell depletion method on circulating gammadelta T cell reconstitution and potential role in the graft-versus-leukemia effect

BACKGROUND

Our laboratory previously reported that leukemia patients who developed > or = 10% gammadelta+ T cells during the first six months after receiving an anti-TCRalphabeta T-cell-depleted (TCD) graft from a partially mismatched related donor (PMRD) had a disease-free survival (DFS) advantage. These gammadelta+ T cells were V81+CD3+CD4-CD8-CD69+HLADR+ and are cytotoxic to K562 cells.

METHODS

In order to determine whether the anti-alphabeta TCD regimen was associated with these findings, we compared the reconstitution of gammadelta+ T cells from patients who received TCD PMRD grafts using the anti-TCRc4 MAb TIOB9-1A31 (previously reported) with similar patients who received grafts using the anti-CD3 MAb OKT3.

RESULTS

Increased cytotoxic Vdelta1+ T cells were seen in 10 of 43 T10B9 TCD patients compared to 7 of 100 in the OKT3 TCD group (23% versus 7%, p = 0.010). T10B9 patients with increased gammadelta+ T cells also exhibited a higher range of increased gammadelta+ T cells and the length of time the gammadelta+ T cells remained high was longer when compared to OKT3 patients. Patients with increased gammadelta+ T cells whose grafts were T-cell depleted with T10B9 showed a significant decrease in relapse (p = 0.038). Similar rates and reduction in relapse were seen in OKT3 TCD patients, although significance was not reached due to the small number of patients with increased gammadelta+ T cells. Estimated 3 year disease-free survival was significantly improved in T10B9 patients with increased gammadelta+ T cells (0.79 versus 0.31, p = 0.009), a trend also seen in OKT3 patients (p = 0.091).

DISCUSSION

These observations indicate that Vdelta1+CD4-CD8-cytotoxic T cells are associated with lower relapse rates and improved survival, and thus may have a role in a graft-versus-leukemia effect.

CD34+ cells obtained from "good mobilizers" are more activated and exhibit lower ex vivo expansion efficiency than their counterparts from "poor mobilizers"

BACKGROUND

The classification of patients into "good" or "poor" mobilizers is based on CD34+ cell count in their peripheral blood (PB) after granulocyte-colony-stimulating factor (G-CSF) injection. We hypothesized that, apart from their mobilization from marrow to the blood, the response to G-CSF of CD34+ cells also includes activation of proliferation, metabolic activity, and proliferative capacity.

STUDY DESIGN AND METHODS

Mobilized PB CD34+ cells purified from samples obtained by cytapheresis of multiple myeloma or non-Hodgkin's lymphoma patients of both good (>50 CD34+ cells/microL) and poor (< or =50 CD34+ cells/microL) mobilizers were studied. The initial cell cycle state of CD34+ cells after selection and their kinetics of activation (exit from G(0) phase) during ex vivo culture were analyzed. Their proliferative capacity was estimated on the basis of ex vivo generation of total cells, CD34+ cells, and colony-forming cells (CFCs), in a standardized expansion culture. Indirect insight in metabolic activity was obtained on the basis of their survival (viability and apoptosis follow-up) during the 7-day-long conservation in hypothermia (4 degrees C) in the air or in atmosphere containing 3% O(2)/6% CO(2).

RESULTS

CD34+ cells obtained from good mobilizers were in lower proportion in the G(0) phase, their activation in a cytokine-stimulated culture was accelerated, and they exhibited a lower ex vivo expansion efficiency than those from poor mobilizers. The resistance to hypothermia of good immobilizers' CD34+ cells is impaired.

CONCLUSION

A good response to G-CSF mobilization treatment is associated with a higher degree of proliferative and metabolic activation of mobilized CD34+ cells with a decrease in their expansion capacity.

Gammadelta T cells in EAE: early trafficking events and cytokine requirements

We have previously shown that gammadelta T cells traffic to the CNS during EAE with concurrently increased expression of beta(2)-integrins and production of IFN-gamma and TNF-alpha. To extend these studies, we transferred bioluminescent gammadelta T cells to WT mice and followed their movement through the acute stages of disease. We found that gammadelta T cells rapidly migrated to the site of myelin oligodendrocyte glycoprotein peptide injection and underwent massive expansion. Within 6 days after EAE induction, bioluminescent gammadelta T cells were found in the spinal cord and brain, peaking in number between days 10 and 12 and then rapidly declining by day 15. Reconstitution of gammadelta T cell(-/-) mice with gammadelta T cells derived from beta(2)-integrin-deficient mice (CD11a, -b or -c) demonstrated that gammadelta T-cell trafficking to the CNS during EAE is independent of this family of adhesion molecules. We also examined the role of gammadelta T-cell-produced IFN-gamma and TNF-alpha in EAE and found that production of both cytokines by gammadelta T cells was required for full development of EAE. These results indicate that gammadelta T cells are critical for the development of EAE and suggest a therapeutic target in demyelinating disease.

Allicin inhibits SDF-1alpha-induced T cell interactions with fibronectin and endothelial cells by down-regulating cytoskeleton rearrangement, Pyk-2 phosphorylation and VLA-4 expression

Allicin, a major ingredient of fresh garlic extract that is produced during the crushing of garlic cloves, exerts various beneficial biological effects, including a broad spectrum of antimicrobial activity, antihyperlipidaemic and antihypertensive effects. However, how allicin affects the immune system is less well known, and its effect on human T cells has never been studied. Here, we examined the in-vitro effects of allicin on the functioning of T cells related to their entry to inflamed extravascular sites. We found that allicin (20-100 microm) inhibits the SDF-1alpha (CXCL12)-induced T cell migration through fibronectin (FN), and that this inhibition is mediated by the down-regulation of (i) the reorganization of cortical actin and the subsequent T cell polarization, and (ii) T cell adhesion to FN. Moreover, allicin also inhibited T cell adhesion to endothelial cells and transendothelial migration. The mechanisms underlying these inhibitory effects of allicin are associated with its ability to down-regulate the phosphorylation of Pyk2, an intracellular member of the focal adhesion kinases, and to reduce the expression of the VCAM-1- and FN-specific alpha4beta1-integrin (VLA-4). The ability of allicin to down-regulate these chemokine-induced and VLA-4-mediated T cell functions explains its beneficial biological effects in processes where T cells play an important role and suggests that allicin may be used therapeutically with chronic inflammatory diseases.

Differential effects of treatment with a small-molecule VLA-4 antagonist before and after onset of relapsing EAE

Interaction of very late antigen-4 (VLA-4) with its ligand vascular cell adhesion molecule-1 (VCAM-1) is required for central nervous system (CNS) migration of encephalitogenic T cells in relapsing experimental autoimmune encephalomyelitis (R-EAE). Anti-VLA-4 monoclonal antibody (mAb) treatment prior to EAE onset inhibits disease induction; however, treatment initiated after the appearance of clinical symptoms increases relapse rates, augments Th1 responses, and enhances epitope spreading perhaps due to the activation of costimulatory signals. To negate the potential costimulatory activity of intact anti-VLA-4, we examined the ability of BIO 5192, a small-molecule VLA-4 antagonist, to regulate active proteolipid protein 139-151 (PLP139-151)-induced R-EAE. BIO 5192 administered one week after peptide priming (ie, before clinical disease onset) delayed the clinical disease onset but led to severe disease exacerbation upon treatment removal. BIO 5192 treatment initiated during disease remission moderately enhanced clinical disease while mice were on treatment and also resulted in posttreatment exacerbation. Interestingly, BIO 5192 treatment begun at the peak of acute disease accelerated entrance into disease remission and inhibited relapses, but treatment removal again exacerbated disease. Enhanced disease was caused by the release of encephalitogenic cells from the periphery and the rapid accumulation of T cells in the CNS. Collectively, these results further demonstrate the complexity of VLA-4/VCAM interactions, particularly in a relapsing-remitting autoimmune disease.

Lactate stimulates fibroblast expression of hyaluronan and CD44: the Warburg effect revisited

Hyaluronan, a high-molecular-weight glycosaminoglycan of the extracellular matrix, is prominent during rapid tissue growth and repair. It stimulates cell motility and hydrates tissue, providing an environment that facilitates cell movement. Markedly enhanced levels of hyaluronan also occur in the stroma surrounding human cancers, thus providing an environment that promotes spread of cancer cells. The ability of malignant tumors to generate lactate, even in the presence of adequate oxygen, is known as the Warburg effect. Early in wound healing as blood and oxygen supply decrease, lactate levels increase, as does stromal hyaluronan, suggesting a cause-and-effect relationship. Similarly, peritumor stromal fibroblast hyaluronan may be a response to cancer cell lactate. To test this, fibroblasts were cultured in the presence of lactate. With increasing lactate, higher levels of hyaluronan were observed, as were levels of CD44 expression, the predominant receptor for hyaluronan. The ability of tumor cells to utilize anaerobic metabolism and to generate lactate, even in the presence of adequate supplies of oxygen, may be one of the mechanisms used to recruit host fibroblasts to deposit hyaluronan and to express CD44, thereby participating in the process of cancer invasion and metastasis.

Regulation of T-cell interaction with fibronectin by transforming growth factor-beta is associated with altered Pyk2 phosphorylation

Although the involvement of transforming growth factor-beta (TGF-beta) in inflammatory reactions has been extensively studied, its mode of action in the context of the extracellular matrix (ECM) is still not fully understood. We undertook this study in an attempt to reveal the putative roles of TGF-beta in T-cell adhesion and migration. We found that a 60-min treatment of T cells with TGF-beta regulates T-cell adhesion to fibronectin (FN), a prototype cell adhesion protein of the ECM, depending on the presence of other activators. At 5 pg/ml to 1 ng/ml, TGF-beta alone induced T-cell adhesion to FN in an integrin alpha4/beta1- and integrin alpha5/beta1-dependent manner. TGF-beta also attenuated T-cell migration on the stromal cell-derived factor (SDF)-1alpha gradients. These effects of TGF-beta were not accompanied by alteration in the expression of very-late activation antigen type 4 (VLA-4) and VLA-5, nor were they mediated by the cyclo-oxygenase pathway. The cellular mechanism underlying the adhesion-regulating activities of TGF-beta involves adhesion-associated cytoskeletal elements. TGF-beta induced the phosphorylation of focal adhesion kinase Pyk2, but not extracellular signal-regulated kinase (ERK), and this effect was markedly increased in the presence of immobilized FN, suggesting a collaborative role for FN-specific integrins. Indeed, TGF-beta-induced Pyk2 phosphorylation was inhibited by monoclonal antibodies against VLA-4, VLA-5 and CD29. Thus, TGF-beta, which may appear at extravascular sites during inflammation, affects the adhesion of T cells to ECM glycoproteins and their migration by its ability to differentially induce or inhibit the phosphorylation of Pyk2.

Discordant effects of anti-VLA-4 treatment before and after onset of relapsing experimental autoimmune encephalomyelitis

Initial migration of encephalitogenic T cells to the central nervous system (CNS) in relapsing experimental autoimmune encephalomyelitis (R-EAE), an animal model of multiple sclerosis (MS), depends on the interaction of the alpha4 integrin (VLA-4) expressed on activated T cells with VCAM-1 expressed on activated cerebrovascular endothelial cells. Alternate homing mechanisms may be employed by infiltrating inflammatory cells after disease onset. We thus compared the ability of anti-VLA-4 to regulate proteolipid protein (PLP) 139-151-induced R-EAE when administered either before or after disease onset. Preclinical administration of anti-VLA-4 either to naive recipients of primed encephalitogenic T cells or to mice 1 week after peptide priming, i.e., before clinical disease onset, inhibited the onset and severity of clinical disease. In contrast, Ab treatment either at the peak of acute disease or during remission exacerbated disease relapses and increased the accumulation of CD4(+) T cells in the CNS. Most significantly, anti-VLA-4 treatment either before or during ongoing R-EAE enhanced Th1 responses to both the priming peptide and endogenous myelin epitopes released secondary to acute tissue damage. Collectively, these results suggest that treatment with anti-VLA-4 Ab has multiple effects on the immune system and may be problematic in treating established autoimmune diseases such as MS.

Crosslinking CD81 results in activation of TCRgammadelta T cells

CD81 is expressed on most cells and is associated with other glycoproteins, including CD4 and CD8, to form multimolecular membrane complexes. Crosslinking of CD81 on TCRalphabeta(+) T cells results in costimulatory signals that have been proposed to be mediated via CD4 or CD8. In this study, we show that CD81 is also expressed on TCRgammadelta(+)CD4(-)CD8(-) T cells. CD81 crosslinking greatly enhanced anti-CD3 activation of both TCRalphabeta(+) (CD4+ and CD8+) and TCRgammadelta(+) T cells with regard to IFN-gamma production. However, crosslinking of CD81 molecules on TCRgammadelta(+) T cells, in the absence of anti-CD3 stimulation, resulted in cytokine production and enhanced IL-2-induced proliferation, demonstrating that physical association with CD4 or CD8 is not necessary for CD81 signaling. In contrast, crosslinking of CD81 on TCRalphabeta(+) T cells, in the absence of anti-CD3 stimulation, failed to activate these T cells. These results suggest that CD81 signaling may be mediated via a different mechanism(s) in TCRgammadelta(+) versus TCRalphabeta(+) T cells.

alpha4 and alpha5 integrins costimulate the CD3-dependent proliferation of fetal thymocytes

Although integrin receptors have been shown to function as costimulatory molecules on mature thymocytes and T cells, it is not known whether these receptors can function as costimulatory molecules on immature thymocytes. Previous studies have shown that the expression of alpha4 and alpha5 integrins were significantly higher on immature, adult CD4(-)CD8(-) thymocytes than on either mature thymocytes or T cells, suggesting that these receptors are involved in early thymocyte development. In this study, we show that day 16 fetal thymocytes express levels of alpha4 and alpha5 equivalent to those of adult CD4(-)CD8(-) thymocytes. Immobilized fibronectin, a ligand for alpha4 and alpha5 integrins, was found to enhance the CD3-dependent proliferation of these fetal thymocytes. In the presence of IL-7, the magnitude of the proliferative response increased with time of incubation, resulting in a dramatic increase in the percentage of gammadelta thymocytes. The enhancement of proliferation by fibronectin was abrogated by soluble antibodies against alpha4 and alpha5, whereas immobilized mAb to alpha4 and alpha5 substituted for fibronectin in enhancing CD3-dependent proliferation, demonstrating that alpha4 and alpha5 integrins were responsible for the enhanced proliferation by fibronectin. Anti-alpha4 mAb enhanced proliferation of fetal thymocytes by 100%, whereas anti-alpha5 mAb and anti-CD28 mAb enhanced proliferation by 25%. Other costimulatory molecules, such as CD2, FcRgamma, and Thy-1, had no effect on the CD3-dependent proliferation of day 16 fetal thymocytes. This study demonstrates that alpha4 and alpha5 integrins are capable of costimulating fetal thymocytes.

Phosphorylation stabilizes alternatively spliced CD44 mRNA transcripts in breast cancer cells: inhibition by antisense complementary to casein kinase II mRNA

CD44, the predominant vertebrate cell surface receptor for hyaluronan, exists in a variety of isoforms resulting from alternative splicing of a single gene. Particular spliced variants of CD44 correlate with increased cell motility, and with poor clinical prognosis in several kinds of carcinomas. Combinations of 9 variant exons that confer this enhanced motility on tumor cells are inserted into a single site in the middle of the extracellular domain of CD44. Evidence suggests that phosphorylation of 2 serine residues in the intracellular domain of CD44 are involved in controlling these events. However, evidence is lacking as to the nature of such kinases. Acidic amino acids in close proximity to these 2 serine residues suggests casein kinase II (CKII) is involved. We now show an antisense phosphorothioate oligonucleotide designed to hybridize to the AUG translation initiation codon of subunit CKII alpha' mRNA blocks in vivo phosphorylation of CD44 in MDA231 breast tumor cells, and at the protein level decreases ectopic expression of total CD44 as well as the metastatic v-7 CD44 isoform. Furthermore subplateau RT-PCR analysis demonstrated antisense transfected MDA231 tumor cells had significant down-regulated or eliminated mRNA transcripts of metastatic CD44 isoforms. CKII as a CD44-associated serine kinase therefore may serve as an important molecule in a signaling cascade that produces a variety of cellular responses in MDA231 breast cancer cells. Since the 3'-untranslated region of CD44 mRNA contain 4 dispersed AUUUA sequences which serve as signals targeting mRNA for rapid turnover, a mechanism is proposed by which CD44 phosphorylation mediates labile message stabilization, hence providing insights into the processes involved in cancer cell growth, invasion and metastasis.