A minimal promoter region of Kit gene recapitulates mast cell differentiation in development, aging and inflammation

To follow mast cells (MCs) distribution during aging and inflammation, we characterized two transgenic mouse models in which the EGFP expression is controlled by 9kb or 12kb of Kit gene promoter, defined as p18 and p70, respectively. We detected EGFP-positive cells in the serosal surfaces of the peritoneum, pleuras and pericardium, mucosal cavities, and connective tissue of almost all organs including gonads of p70, but not of p18 mice. By FACS and immunofluorescence for FcεR1, Kit and β7-integrin, we found that these EGFP positive cells were MCs. In non-inflammatory conditions, a higher percentage of EGFP positive cells was found in juvenile with respect to adult serosal surfaces, but no differences between males and females at both developmental ages. We found, however, a striking difference in developing gonads, with low numbers of EGFP positive cells in foetal ovaries compared to age matched testes. Under inflammatory conditions caused by high fat diet (HFD), mice showed an increase in serosal EGFP positve cells. Altogether our results identify a regulatory region of the Kit gene, activated in MCs and that directing EGFP expression, can be employed to trace this immune cell type throughout the organism and in different animal conditions.

Proinflammatory mucosal-associated invariant CD8+ T cells react to gut flora yeasts and infiltrate multiple sclerosis brain

The composition of the intestinal microbiota plays a critical role in shaping the immune system. Modern lifestyle, the inappropriate use of antibiotics, and exposure to pollution have significantly affected the composition of commensal microorganisms. The intestinal microbiota has been shown to sustain inappropriate autoimmune responses at distant sites in animal models of disease, and may also have a role in immune-mediated central nervous system (CNS) diseases such as multiple sclerosis (MS). We studied the composition of the gut mycobiota in fecal samples from 27 persons with MS (pwMS) and in 18 healthy donors (HD), including 5 pairs of homozygous twins discordant for MS. We found a tendency towards higher fungal abundance and richness in the MS group, and we observed that MS twins showed a higher rate of food-associated strains, such as Saccharomyces cerevisiae. We then found that in pwMS, a distinct population of cells with antibacterial and antifungal activity is expanded during the remitting phase and markedly decreases during clinically and/or radiologically active disease. These cells, named MAIT (mucosal-associated invariant T cells) lymphocytes, were significantly more activated in pwMS compared to HD in response to S. cerevisiae and Candida albicans strains isolated from fecal samples. This activation was also mediated by fungal-induced IL-23 secretion by innate immune cells. Finally, immunofluorescent stainings of MS post-mortem brain tissues from persons with the secondary progressive form of the disease showed that MAIT cells cross the blood–brain barrier (BBB) and produce pro-inflammatory cytokines in the brain. These results were in agreement with the hypothesis that dysbiosis of the gut microbiota might determine the inappropriate response of a subset of pathogenic mucosal T cells and favor the development of systemic inflammatory and autoimmune diseases.

Assessment of T-cell Reactivity to the SARS-CoV-2 Omicron Variant by Immunized Individuals

IMPORTANCE

The emergence of the highly contagious Omicron variant of SARS-CoV-2 and the findings of a significantly reduced neutralizing potency of sera from individuals with previous SARS-CoV-2 infection or vaccination highlights the importance of studying cellular immunity to estimate the degree of immune protection to the new SARS-CoV-2 variant.

OBJECTIVE

To determine T-cell reactivity to the Omicron variant in individuals with established (natural and/or vaccine-induced) immunity to SARS-CoV-2.

DESIGN, SETTING, AND PARTICIPANTS

This was a cohort study conducted between December 20 and 21, 2021, at the Santa Lucia Foundation Istituto di Ricovero e Cura a Carattere Scientifico, Rome, Italy, among health care worker and scientist volunteers. Lymphocytes from freshly drawn blood samples were isolated and immediately tested for reactivity to the spike protein of SARS-CoV-2.

MAIN OUTCOMES AND MEASURES

The main outcomes were the measurement of T-cell reactivity to the mutated regions of the spike protein of the Omicron BA.1 SARS-CoV-2 variant and the assessment of remaining T-cell immunity to the spike protein by stimulation with peptide libraries.

RESULTS

A total of 61 volunteers (mean (range) age, 41.62 (21-62) years; 38 women [62%]) with different vaccination and SARS-CoV-2 infection backgrounds were enrolled. The median (range) frequency of CD4+ T cells reactive to peptides covering the mutated regions in the Omicron variant was 0.039% (0%-2.356%), a decrease of 64% compared with the frequency of CD4+ cells specific for the same regions of the ancestral strain (0.109% [0%-2.376%]). Within CD8+ T cells, a median (range) of 0.02% (0%-0.689%) of cells recognized the mutated spike regions, while 0.039% (0%-3.57%) of cells were reactive to the equivalent unmutated regions, a reduction of 49%. However, overall reactivity to the peptide library of the full-length protein was largely maintained (estimated 87%). No significant differences in loss of immune recognition were identified between groups of participants with different vaccination or infection histories.

CONCLUSIONS AND RELEVANCE

This cohort study of immunized adults in Italy found that despite the mutations in the spike protein, the SARS-CoV-2 Omicron variant was recognized by the cellular component of the immune system. It is reasonable to assume that protection from hospitalization and severe disease will be maintained.

Nanovesicles released by OKT3 hybridoma express fully active antibodies

Recent findings have shown that nanovesicles preparations from either primary immune cells culture supernatants or plasma contain immunoglobulins, suggesting that a natural way of antibody production may be through exosome release. To verify this hypothesis, we used the OKT3 hybridoma clone, which produces a murine IgG2a monoclonal antibody used to reduce rejection in patients undergoing organ transplantation. We showed exosome-associated immunoglobulins in hybridoma supernatants, by Western blot, nanoscale flow cytometry and immunocapture-based ELISA. The OKT3-exo was also being able to trigger cytokines production in both CD4 and CD8 T cells. These results show that nanovesicles contain immunoglobulin and could be used for immunotherapy. These data could lead to a new approach to improve the effectiveness of therapeutic antibodies by exploiting their natural property to be expressed on nanovesicle membrane, that probably render them more stable and as a consequence more capable to interact with their specific ligand in the best way.

Characterization of a natural variant of human NDP52 and its functional consequences on mitophagy

The role of mitophagy, a process that allows the removal of damaged mitochondria from cells, remains unknown in multiple sclerosis (MS), a disease that is found associated with dysfunctional mitochondria. Here we have qualitatively and quantitatively studied the main players in PINK1-mediated mitophagy in peripheral blood mononuclear cells (PBMCs) of patients with relapsing-remitting MS. We found the variant c.491G>A (rs550510, p.G140E) of NDP52, one of the major mitophagy receptor genes, associated with a MS cohort. Through the characterization of this variant, we discovered that the residue 140 of human NDP52 is a crucial modulator of NDP52/LC3C binding, promoting the formation of autophagosomes in order to drive efficient mitophagy. In addition, we found that in the PBMC population, NDP52 is mainly expressed in B cells and by ensuring efficient mitophagy, it is able to limit the production of the proinflammatory cytokine TNF-α following cell stimulation. In sum, our results contribute to a better understanding of the role of NDP52 in mitophagy and underline, for the first time, a possible role of NDP52 in MS.

CD44v8-10 is a marker for malignant traits and a potential driver of bone metastasis in a subpopulation of prostate cancer cells

OBJECTIVE

Bone metastasis is a clinically important outcome of prostate carcinoma (PC). We focused on the phenotypic and functional characterization of a particularly aggressive phenotype within the androgen-independent bone metastasis-derived PC3 cell line. These cells, originated from the spontaneous conversion of a CD44-negative subpopulation, stably express the CD44v8-10 isoform (CD44v8-10pos) and display stem cell-like features and a marked invasive phenotype in vitro that is lost upon CD44v8-10 silencing.

METHODS

Flow cytometry, enzyme-linked immunoassay, immunofluorescence, and Western blot were used for phenotypic and immunologic characterization. Real-time quantitative polymerase chain reaction and functional assays were used to assess osteomimicry.

RESULTS

Analysis of epithelial-mesenchymal transition markers showed that CD44v8-10pos PC3 cells surprisingly display epithelial phenotype and can undergo osteomimicry, acquiring bone cell phenotypic and behavioral traits. Use of specific siRNA evidenced the ability of CD44v8-10 variant to confer osteomimetic features, hence the potential to form bone-specific metastasis. Moreover, the ability of tumors to activate immunosuppressive mechanisms which counteract effective immune responses is a sign of the aggressiveness of a tumor. Here we report that CD44v8-10pos cells express programmed death ligand 1, a negative regulator of anticancer immunity, and secrete exceptionally high amounts of interleukin-6, favoring osteoclastogenesis and immunosuppression in bone microenvironment. Notably, we identified a novel pathway activated by CD44v8-10, involving tafazzin (TAZ) and likely the Wnt/TAZ axis, known to play a role in upregulating osteomimetic genes.

CONCLUSIONS

CD44v8-10 could represent a marker of a more aggressive bone metastatic PC population exerting a driver role in osteomimicry in bone. A novel link between TAZ and CD44v8-10 is also shown.

Sexually Dimorphic Immune and Neuroimmune Changes Following Peripheral Nerve Injury in Mice: Novel Insights for Gender Medicine

Neuropathic pain (NeP) in humans is often a life-long condition with no effective therapy available. The higher incidence of female gender in NeP onset is worldwide reported, and although the cause is generally attributed to sex hormones, the actual mechanisms and the players involved are still unclear. Glial and immune cells take part in NeP development, and orchestrate the neuroimmune and inflammatory response, releasing pro-inflammatory factors with chemoattractant properties that activate resident immune cells and recruit immune cells from circulation. The neuro-immune crosstalk is a key contributor to pain hypersensitivity following peripheral nervous system injury. Our previous works showed that in spite of the fact that female mice had an earlier analgesic response than males following nerve lesion, the recovery from NeP was never complete, suggesting that this difference could occur in the very early stages after injury. To further investigate gender differences in immune and neuroimmune responses to NeP, we studied the main immune cells and mediators elicited both in plasma and sciatic nerves by peripheral nerve lesion. After injury, we found a different pattern of distribution of immune cell populations showing either a higher infiltration of T cells in nerves from females or a higher infiltration of macrophages in nerves from males. Moreover, in comparison to male mice, the levels of cytokines and chemokines were differently up- and down-regulated in blood and nerve lysates from female mice. Our study provides some novel insights for the understanding of gender-associated differences in the generation and perseveration of NeP as well as for the isolation of specific neurodegenerative mechanisms underlying NeP. The identification of gender-associated inflammatory profiles in neuropathy is of key importance for the development of differential biomarkers and gender-specific personalized medicine.

Plasmatic exosomes from prostate cancer patients show increased carbonic anhydrase IX expression and activity and low pH

Acidity, hypoxia and increased release of exosomes are severe phenotypes of tumours. The regulation of pH in tumours involves the interaction of several proteins, including the carbonic anhydrases which catalyze the formation of bicarbonate and protons from carbon dioxide and water. Among CA isoforms, CA IX is over-expressed in a large number of solid tumours, conferring to cancer cells a survival advantage in hypoxic and acidic microenvironment, but there isn't evidence that CA IX expression could have a real clinical impact. Therefore, in this study for the first time the expression and activity of CA IX have been investigated in the plasmatic exosomes obtained from patients with prostate carcinoma (PCa). For this purpose, the study was performed through different methodological approaches, such as NTA, western blot analysis, enzyme activity assay, Nanoscale flow cytometry, ELISA, confocal microscopy. The results showed that PCa exosomes significantly overexpressed CA IX levels and related activity as compared to healthy donors. Furthermore, CA IX expression and activity were correlated to the exosome intraluminal pH, demonstrating for the first time that PCa exosomes are acidic. Our data suggest the possible use of the exosomal CA IX expression and activity as a biomarker of cancer progression in PCa.

EBV-specific CD8 T lymphocytes and B cells during glatiramer acetate therapy in patients with MS

Objective

Infection with Epstein-Barr virus (EBV) has been associated with clinical activity and risk of developing MS. The purpose of this study is to investigate the impact of glatiramer acetate (GA) therapy on EBV-specific immune responses and disease course.

Methods

We characterized EBV-specific CD8 T lymphocytes and B cells during disease-modifying treatments in 2 groups of patients with MS. We designed a 2-pronged approach consisting of a cross-sectional study (39 untreated patients, 38 patients who had undergone 12 months of GA treatment, and 48 healthy donors compatible for age and sex with the patients with MS) and a 12-month longitudinal study (35 patients treated with GA). CD8 EBV-specific T cells and B lymphocytes were studied using pentamers and multiparametric flow cytometry.

Results

We find that treatment with GA enhances viral recognition by inducing an increased number of circulating virus-specific CD8 T cells (p = 0.0043) and by relieving their features of exhaustion (p = 0.0053) and senescence (p < 0.0001, p = 0.0001). B cells, phenotypically and numerically tracked along the 1-year follow-up study, show a steady decrease in memory B-cell frequencies (p = 0.025), paralleled by an increase of the naive B subset.

Conclusion

GA therapy acts as a disease-modifying therapy restoring homeostasis in the immune system, including anti-EBV responses.

Increased Plasmatic Levels of PSA-Expressing Exosomes Distinguish Prostate Cancer Patients from Benign Prostatic Hyperplasia: A Prospective Study

Prostate Specific Antigen (PSA) fails to discriminate between benign prostatic hyperplasia (BPH) and Prostate Cancer (PCa), resulting in large numbers of unnecessary biopsies and missed cancer diagnoses. Nanovesicles called exosomes are directly detectable in patient plasma and here we explore the potential use of plasmatic exosomes expressing PSA (Exo-PSA) in distinguishing healthy individuals, BPH, and PCa. Exosomes were obtained from plasma samples of 80 PCa, 80 BPH, and 80 healthy donors (CTR). Nanoparticle Tracking Analysis (NTA), immunocapture-based ELISA (IC-ELISA), and nanoscale flow-cytometry (NSFC), were exploited to detect and characterize plasmatic exosomes. Statistical analysis showed that plasmatic exosomes expressing both CD81 and PSA were significantly higher in PCa as compared to both BPH and CTR, reaching 100% specificity and sensitivity in distinguishing PCa patients from healthy individuals. IC-ELISA, NSFC, and Exo-PSA consensus score (EXOMIX) showed 98% to 100% specificity and sensitivity for BPH-PCa discrimination. This study outperforms the conventional PSA test with a minimally invasive widely exploitable approach.

Human primary macrophages scavenge AuNPs and eliminate it through exosomes. A natural shuttling for nanomaterials

The use of nanomaterials is increasing but the real risk associated with their use in humans has to be defined. In fact, nanomaterials tend to accumulate in organs over a long period of time and are slowly degraded or eliminated by the body. Exosomes are nanovesicles actively shuttle molecules, including chemical products and metals, through the body. Macrophages scavenge the body from both organic and inorganic substances, and they use to release high amounts of exosomes. We hypothesized that macrophages may have a role in eliminating nanomaterials through their exosomes. We treated human primary macrophages with 20 nm gold nanoparticles (AuNPs), analyzing the presence of AuNPs in both cells and the released exosomes by the implementation of different techniques, including SP-ICP-MS and NTA. We showed that macrophages endocytosed AuNPs and released them through exosomes. Our study on one hand provide the evidence for a new methodology in the early identification of the nanomaterials levels in exposed subjects. On the other hand we depict a way our body shuttle virtually intact nanoparticles through macrophage-released exosomes.

Microenvironmental pH and Exosome Levels Interplay in Human Cancer Cell Lines of Different Histotypes

Exosomes are extracellular nanovesicles primarily involved in the pathogenesis of many diseases including cancer. This study was set out from recent evidence that extracellular acidity may increase the exosome release by cancer cells. However, this preliminary evidence did not provide solid information on whether the pH-dependent exosome over-release represents a common feature of all cancers. To the purpose of demonstrating that cancer acidity is a major determinant in inducing an increased exosome release by human cancer cells, we evaluated human tumor cell lines deriving from either colon, breast, prostate cancers, melanoma, or osteosarcoma. All cell lines were cultured in either the current 7.4 pH or the typical pH of cancer that is 6.5. The levels of released extracellular vesicles were measured by protein counts, nanoparticle tracking analysis (NTA), and nanoscale flow cytometry. The results showed that pH 6.5 induced a remarkable increase in exosome release, and buffering the medium significantly reduced the exosome release in all cancers. With these results, we provide, for the first time, evidence that tumor acidity and exosome levels represent common cancer phenotypes.

High-dose ascorbate and arsenic trioxide selectively kill acute myeloid leukemia and acute promyelocytic leukemia blasts in vitro

The use of high-dose ascorbate (ASC) for the treatment of human cancer has been attempted several decades ago and has been recently revived by several in vitro and in vivo studies in solid tumors. We tested the cytotoxic effects of ASC, alone or in combination with arsenic trioxide (ATO) in acute myeloid leukemia (AML) and acute promyelocytic leukemia (APL). Leukemic cell lines and primary blasts from AML and APL patients were treated with graded concentrations of ASC, alone or in association with standard concentration (1 μM) of ATO. The ASC/ATO combination killed myeloid blasts, including leukemic CD34⁺ cells, while sparing CD34⁺ progenitors obtained from normal cord blood and bone marrow. Actually, approximately one-third (11/36) of primary AML cases were highly sensitive to the ASC/ATO combination. The mechanism of cell killing appeared to be related to increased oxidative stress and overproduction of ROS in a non-quantitative fashion, which resulted in induction of apoptosis. These effects were reverted by the addition of the antioxidant N-Acetyl-Cysteine (NAC). In the APL NB4 model, ASC induced direct degradation of the PML and PML/RARA proteins via caspase activation, while the transcriptional repressor DAXX was recruited in re-constituted PML nuclear bodies. Our findings encourage the design of pilot studies to explore the potential clinical benefit of ASC alone or in combination with ATO in advanced AML and APL.

Increased PSA expression on prostate cancer exosomes in in vitro condition and in cancer patients

Prostate specific antigen (PSA) test is the most common, clinically validated test for the diagnosis of prostate cancer (PCa). While neoplastic lesions of the prostate may cause aberrant levels of PSA in the blood, the quantitation of free or complexed PSA poorly discriminates cancer patients from those developing benign lesions, often leading to invasive and unnecessary surgical procedures. Microenvironmental acidity increases exosome release by cancer cells. In this study we evaluated whether acidity, a critical phenotype of malignancy, could influence exosome release and increase the PSA expression in nanovesicles released by PCa cells. To this aim, we exploited Nanoparticle Tracking Analysis (NTA), an immunocapture-based ELISA, and nanoscale flow-cytometry. The results show that microenvironmental acidity induces an increased release of nanovesicles expressing both PSA and the exosome marker CD81. In order to verify whether the changes induced by the local selective pressure of extracellular acidity may correspond to a clinical pathway we used the same approach to evaluate the levels of PSA-expressing exosomes in the plasma of PCa patients and controls, including subjects with benign prostatic hypertrophy (BPH). The results show that only PCa patients have high levels of nanovesicles expressing both CD81 and PSA. This study shows that tumor acidity exerts a selective pressure leading to the release of extracellular vesicles that express both PSA and exosome markers. A comparable scenario was shown in the plasma of prostate cancer patients as compared to both BPH and healthy controls. These results suggest that microenvironmental acidity may represent a key factor which determines qualitatively and quantitatively the release of extracellular vesicles by malignant tumors, including prostate cancer. This condition leads to the spill-over of nanovesicles into the peripheral blood of prostate cancer patients, where the levels of tumor biomarkers expressed by exosomes, such as PSA-exosomes, may represent a novel, non-invasive clinical tool for the screening and early diagnosis of prostate cancer.

Acridine Orange/exosomes increase the delivery and the effectiveness of Acridine Orange in human melanoma cells: A new prototype for theranostics of tumors

Specifically targeted drug delivery systems with low immunogenicity and toxicity are deemed to increase efficacy of cancer chemotherapy. Acridine Orange (AO) is an acidophilic dye with a strong tumoricidal action following excitation with a light source at 466 nm. However, to date the clinical use of AO is limited by the potential side effects elicited by systemic administration. The endogenous nanocarrier exosomes have been recently introduced as a natural delivery system for therapeutic molecules. In this article, we show the outcome of the administration to human melanoma cells of AO charged Exosomes (Exo-AO), in both monolayer and spheroid models. The results showed an extended drug delivery time of Exo-AO to melanoma cells as compared to the free AO, improving the cytotoxicity of AO. This study shows that Exo-AO have a great potential for a real exploitation as a new theranostic approach against tumors based on AO delivered through the exosomes.

A Leukemia-Associated CD34/CD123/CD25/CD99+ Immunophenotype Identifies FLT3-Mutated Clones in Acute Myeloid Leukemia

PURPOSE

We evaluated leukemia-associated immunophenotypes (LAIP) and their correlation with fms-like tyrosine kinase 3 (FLT3) and nucleophosmin (NPM1) gene mutational status in order to contribute a better identification of patients at highest risk of relapse in acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

Bone marrow samples from 132 patients with AML were analyzed by nine-color multiparametric flow cytometry. We confirmed the presence of the mutation in diagnostic samples and in sorted cells by conventional RT-PCR and by patient-specific RQ-PCR.

RESULTS

Within the CD34(+) cell fraction, we identified a discrete population expressing high levels of the IL3 receptor α-chain (CD123) and MIC-2 (CD99) in combination with the IL2 receptor α-chain (CD25). The presence of this population positively correlated with the internal tandem duplications (ITD) mutation in the FLT3 gene (r = 0.71). Receiver operating characteristics showed that, within the CD34(+) cell fraction a percentage of CD123/CD99/CD25(+) cells ≥11.7% predicted FLT3-ITD mutations with a specificity and sensitivity of >90%. CD34/CD123/CD99/CD25(+) clones were also detectable at presentation in 3 patients with FLT3 wild-type/NPM1(+) AML who relapsed with FLT3-ITD/NPM1(+) AML. Quantitative real-time PCR designed at relapse for each FLT3-ITD in these three cases confirmed the presence of low copy numbers of the mutation in diagnostic samples.

CONCLUSIONS

Our results suggest that the CD34/CD25/CD123/CD99(+) LAIP is strictly associated with FLT3-ITD-positive cells.

Epstein-Barr virus genetic variants are associated with multiple sclerosis

OBJECTIVE

We analyzed the Epstein-Barr nuclear antigen 2 (EBNA2) gene, which contains the most variable region of the viral genome, in persons with multiple sclerosis (MS) and control subjects to verify whether virus genetic variants are involved in disease development.

METHODS

A seminested PCR approach and Sanger sequencing were used to analyze EBNA2 in 53 patients and 38 matched healthy donors (HDs). High-throughput sequencing by Illumina MiSeq was also applied in a subgroup of donors (17 patients and 17 HDs). Patients underwent gadolinium-enhanced MRI and human leucocyte antigen typing.

RESULTS

MS risk significantly correlated with an excess of 1.2 allele (odds ratio [OR] = 5.13; 95% confidence interval [CI] 1.84-14.32; p = 0.016) and underrepresentation of 1.3B allele (OR = 0.23; 95% CI 0.08-0.51; p = 0.0006). We identified new genetic variants, mostly 1.2 allele- and MS-associated (especially amino acid variation at position 245; OR = 9.4; 95% CI 1.19-78.72; p = 0.0123). In all cases, the consensus sequence from deep sequencing confirmed Sanger sequencing (including the cosegregation of newly identified variants with known EBNA2 alleles) and showed that the extent of genotype intraindividual variability was higher than expected: rare EBNA2 variants were detected in all HDs and patients with MS (range 1-17 and 3-19, respectively). EBNA2 variants did not seem to correlate with human leucocyte antigen typing or clinical/MRI features.

CONCLUSIONS

Our study unveils a strong association between Epstein-Barr virus genomic variants and MS, reinforcing the idea that Epstein-Barr virus contributes to disease development.

Non-myeloablative autologous haematopoietic stem cell transplantation expands regulatory cells and depletes IL-17 producing mucosal-associated invariant T cells in multiple sclerosis

Autologous haematopoietic stem cell transplantation has been tried as one experimental strategy for the treatment of patients with aggressive multiple sclerosis refractory to other immunotherapies. The procedure is aimed at ablating and repopulating the immune repertoire by sequentially mobilizing and harvesting haematopoietic stem cells, administering an immunosuppressive conditioning regimen, and re-infusing the autologous haematopoietic cell product. 'Non-myeloablative' conditioning regimens to achieve lymphocytic ablation without marrow suppression have been proposed to improve safety and tolerability. One trial with non-myeloablative autologous haematopoietic stem cell transplantation reported clinical improvement and inflammatory stabilization in treated patients with highly active multiple sclerosis. The aim of the present study was to understand the changes in the reconstituted immune repertoire bearing potential relevance to its mode of action. Peripheral blood was obtained from 12 patients with multiple sclerosis participating in the aforementioned trial and longitudinally followed for 2 years. We examined the phenotype and function of peripheral blood lymphocytes by cell surface or intracellular staining and multi-colour fluorescence activated cell sorting alone or in combination with proliferation assays. During immune reconstitution post-transplantation we observed significant though transient increases in the proportion of CD4+ FoxP3+ T cells and CD56(high) natural killer cell subsets, which are cell subsets associated with immunoregulatory function. CD8+ CD57+ cytotoxic T cells were persistently increased after therapy and were able to suppress CD4+ T cell proliferation with variable potency. In contrast, a CD161(high) proinflammatory CD8+ T cell subset was depleted at all time-points post-transplantation. Phenotypic characterization revealed that the CD161(high)CD8+ T cells were mucosal-associated invariant T cells, a novel cell population originating in the gut mucosa but expressing the central nervous system-homing receptor CCR6. Detection of mucosal-associated invariant T cells in post-mortem multiple sclerosis brain white matter active lesions confirmed their involvement in the disease pathology. Intracellular cytokine staining demonstrated interferon γ and interleukin 17 production and lack of interleukin 10 production, a pro-inflammatory profile. Mucosal-associated invariant T cell frequency did not change in patients treated with interferon β; and was more depleted after autologous haematopoietic stem cell transplantation than in patients who had received high-dose cyclophosphamide (n = 7) or alemtuzumab (n = 21) treatment alone, suggesting an additive or synergistic effect of the conditioning regime components. We propose that a favourably modified balance of regulatory and pro-inflammatory lymphocytes underlies the suppression of central nervous system inflammation in patients with multiple sclerosis following non-myeloablative autologous haematopoietic stem cell transplantation with a conditioning regimen consisting of cyclophosphamide and alemtuzumab.

Increased CD8+ T cell response to Epstein-Barr virus lytic antigens in the active phase of multiple sclerosis

It has long been known that multiple sclerosis (MS) is associated with an increased Epstein-Barr virus (EBV) seroprevalence and high immune reactivity to EBV and that infectious mononucleosis increases MS risk. This evidence led to postulate that EBV infection plays a role in MS etiopathogenesis, although the mechanisms are debated. This study was designed to assess the prevalence and magnitude of CD8+ T-cell responses to EBV latent (EBNA-3A, LMP-2A) and lytic (BZLF-1, BMLF-1) antigens in relapsing-remitting MS patients (n = 113) and healthy donors (HD) (n = 43) and to investigate whether the EBV-specific CD8+ T cell response correlates with disease activity, as defined by clinical evaluation and gadolinium-enhanced magnetic resonance imaging. Using HLA class I pentamers, lytic antigen-specific CD8+ T cell responses were detected in fewer untreated inactive MS patients than in active MS patients and HD while the frequency of CD8+ T cells specific for EBV lytic and latent antigens was higher in active and inactive MS patients, respectively. In contrast, the CD8+ T cell response to cytomegalovirus did not differ between HD and MS patients, irrespective of the disease phase. Marked differences in the prevalence of EBV-specific CD8+ T cell responses were observed in patients treated with interferon-β and natalizumab, two licensed drugs for relapsing-remitting MS. Longitudinal studies revealed expansion of CD8+ T cells specific for EBV lytic antigens during active disease in untreated MS patients but not in relapse-free, natalizumab-treated patients. Analysis of post-mortem MS brain samples showed expression of the EBV lytic protein BZLF-1 and interactions between cytotoxic CD8+ T cells and EBV lytically infected plasma cells in inflammatory white matter lesions and meninges. We therefore propose that inability to control EBV infection during inactive MS could set the stage for intracerebral viral reactivation and disease relapse.

CD161(high)CD8+T cells bear pathogenetic potential in multiple sclerosis

To identify differentially expressed genes in multiple sclerosis, microarrays were used in a stringent experimental setting-leukapheresis from disease-discordant monozygotic twins and gene expression profiling in CD4(+) and CD8(+) T-cell subsets. Disease-related differences emerged only in the CD8(+) T-cell subset. The five differentially expressed genes identified included killer cell lectin-like receptor subfamily B, member 1, also known as natural killer receptor protein 1a/CD161, presented by the International Multiple Sclerosis Genetics Consortium as one of the non-MHC candidate loci. Flow cytometric analysis on peripheral blood of healthy donors and patients with multiple sclerosis and rheumatoid arthritis confirmed an upregulation of CD161 at the protein level, showing also a significant excess of CD161(high)CD8(+) T cells in multiple sclerosis. This subset prevalently included chemokine (C-C motif) receptor 6(+), cytokine-producing, effector-memory T cells with proinflammatory profiles. It also included all circulating interleukin-17(+)CD8(+) T cells. In the CD161(high)CD8(+) subset, interleukin-12 facilitated proliferation and interferon-γ production, with CD161 acting as a co-stimulatory receptor. CD161(+)CD8(+)CD3(+) T cells producing interferon-γ were part of intralesional immune infiltrates and ectopic B cell follicles in autopsy multiple sclerosis brains. Variations of CD161 expression on CD8(+) T cells identify a subset of lymphocytes with proinflammatory characteristics that have not been previously reported in multiple sclerosis and are likely to contribute to disease immunopathology.

NKG2A inhibits NKG2C effector functions of γδ T cells: implications in health and disease

The CD94/NKG2 complex is expressed on T and NK lymphocytes. CD94 molecules covalently associate to activating or inhibitory NKG2 molecules, and their expression finely tunes cell responses. Human γδ T cells express several NKRs. Expression of these receptors is confined to the cytolytic Vδ2 subset, which coexpresses the FcγRIII CD16 and CD45RA and has been defined as Vγ9Vδ2 T(EMRA) cells. We show that the CD94/NKG2C complex, associated with KARAP/DAP12, is fully functional in γδ T cells, as determined by measuring IFN-γ production, T cell proliferation, and cytolytic activity by γδ lymphocytes. In contrast, NKG2A expression was found on all γδ T cell memory subsets, suggesting a crucial role of the inhibitory signal provided by this receptor on γδ T cell responses. Moreover, we found Vγ9Vδ2 T(EMRA), NK, and CD8+ αβ T cells coexpressing NKG2A and NKG2C receptors. Functional experiments showed that the inhibitory signal mediated by the NKG2A receptor prevails when double-positive cells are activated. Finally, NKG2A expression on γδ LDGL correlates with asymptomatic pathology, even in the presence of NKG2C coexpression, whereas in symptomatic patients affected by severe disease, the inhibitory NKG2A receptor is absent, and a variety of activatory NKRs was found. We propose that the silent behavior of γδ cells in LDGL patients is a result of effective inhibitory HLA class I receptors.

Cystic fibrosis transmembrane conductance regulator (CFTR) expression in human platelets: impact on mediators and mechanisms of the inflammatory response

Inflammatory lung disease is a primary cause of morbidity and mortality in cystic fibrosis (CF). Mechanisms of unresolved acute inflammation in CF are not completely known, although the involvement of cystic fibrosis transmembrane conductance regulator (CFTR) in nonrespiratory cells is emerging. Here we examined CFTR expression and function in human platelets (PLTs) and found that they express a biologically active CFTR. CFTR blockade gave an ∼50% reduction in lipoxin A(4) (LXA(4)) formation during PLT/polymorphonuclear leukocytes (PMN) coincubations by inhibiting the lipoxin synthase activity of PLT 12-lipoxygenase. PLTs from CF patients generated ∼40% less LXA(4) compared to healthy subject PLTs. CFTR inhibition increased PLT-dependent PMN viability (33.0±5.7 vs. 61.2±8.2%; P=0.033), suppressed nitric oxide generation (0.23±0.04 vs. 0.11±0.002 pmol/10(8) PLTs; P=0.004), while reducing AKT (1.02±0.12 vs. 0.71±0.007 U; P=0.04), and increasing p38 MAPK phosphorylation (0.650±0.09 vs. 1.04±0.24 U; P=0.03). Taken together, these findings indicate that PLTs from CF patients are affected by the molecular defect of CFTR. Moreover, this CF PLT abnormality may explain the failure of resolution in CF.

TLR stimulation of prostate tumor cells induces chemokine-mediated recruitment of specific immune cell types

TLRs boost antimicrobial response mechanisms by epithelial cells and represent the first line of defense at mucosal sites. In view of these immunomodulatory properties, TLR stimulation may represent a novel means to activate anticancer immune responses. In the present study, the ability of TLR ligands to affect the recruitment of different immune cell populations by human prostate cancer cell lines and the underlying mechanisms were investigated. We showed that LNCaP and DU-145 cells express functionally active TLR3 and TLR5. Treatment with their respective agonists, polyinosinic:polycytidylic acid and flagellin, rapidly triggered NF-kappaB-dependent upregulation of different inflammatory molecules, as assayed by microarray and ELISA. Furthermore, we demonstrated that conditioned media from polyinosinic:polycytidylic acid- and flagellin-treated LNCaP and DU-145 cells induced the recruitment of different leukocyte subpopulations, suggesting that TLR stimulation is able to activate the earliest step of immune response mediated by soluble factors. Interestingly, the more aggressive cancer cell line PC3 expressed TLR3 and TLR5 but failed to respond to TLR agonists in terms of NF-kappaB activation and the ability to attract immune effectors. Overall, these data show for the first time that TLR3 and TLR5 stimulation of human prostate cancer cells triggers the production of chemokines, which, in turn, favor the attraction of immune effectors, thereby representing a tool to enhance the efficacy of conventional therapies by stimulating anticancer immune responses.

Thymoma-associated immunodeficiency: a syndrome characterized by severe alterations in NK, T and B-cells and progressive increase in naïve CD8+ T Cells

Thymomas are rare tumours that sustain T-lymphopoiesis and trigger a variety of autoimmune diseases and immunodeficiencies, including a fatal hypogammaglobulinemia, namely Goods Syndrome (GS). Due to its rarity, GS has been poorly investigated and immunological features, as well as pathogenetic mechanisms underlying this syndrome, are unclear. We studied 30 thymoma patients by performing an immunological assessment, including immunophenotype and analysis of T cell repertoire (TCR). Development of GS was characterized by a progressive decrease in B, CD4 T and NK lymphocytes. These alterations paired with accumulation of CD8+CD45RA+ T cells that showed a polyclonal repertoire without expansions of specific clonotypes. GS is defined as hypogammaglobulinemia with thymoma. Here, we show for the first time that this syndrome is characterized by a severe loss of CD4+, NK and B cells. Furthermore, the accumulation of CD8+CD45RA+ T lymphocytes parallels these changes; this accumulation may have a role in determining the disease and can be used to monitor clinical stages of immunodeficiency in thymoma.

The RNA-binding protein Sam68 contributes to proliferation and survival of human prostate cancer cells

The tyrosine kinase Src is frequently activated in advanced human prostate carcinomas and its activation correlates with tyrosine phosphorylation of the RNA-binding protein Sam68. Herein, we have investigated the expression and function of Sam68 in human prostate cancer cells. Analysis of specimens obtained from 20 patients revealed that Sam68 is upregulated at the protein level in 35% of the samples. Real-time polymerase chain reaction confirmed the results at the mRNA level in most patients. Downregulation of Sam68 by RNAi in LNCaP prostate cancer cells delayed cell cycle progression and reduced the proliferation rate. Moreover, depletion of Sam68 sensitized cells to apoptosis induced by DNA-damaging agents. Similarly, stable cell lines expressing a truncated GFP-Sam68(GSG) protein displayed reduced growth rates and higher sensitivity to cisplatin-induced apoptosis. Microarray analyses revealed that a subset of genes involved in proliferation and apoptosis were altered when Sam68 was knocked down in LNCaP cells. Our results indicate that Sam68 expression supports prostate cancer cells proliferation and survival to cytotoxic agents.

Mitochondrial damage modulates alternative splicing in neuronal cells: implications for neurodegeneration

Mitochondrial damage is linked to many neurodegenerative conditions, such as Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. These diseases are associated with changes in the splicing pattern of individual mRNAs. Here, we tested the hypothesis that mitochondrial damage modulates alternative splicing, not only of a few mRNAs, but in a general manner. We incubated cultured human neuroblastoma cells with the chemical agent paraquat (a neurotoxin that interferes with mitochondrial function, causing energy deficit and oxidative stress) and analysed the splicing pattern of 13 genes by RT-PCR. For all mRNAs that are alternatively spliced, we observed a dose- and time-dependent increase of the smaller isoforms. In contrast, splicing of all constitutive splicing exons that we monitored did not change. Using other drugs, we show that the modulation of alternative splicing correlates with ATP depletion, not with oxidative stress. Such drastic changes in alternative splicing are not observed in cell lines of non-neuronal origin, suggesting a selective susceptibility of neuronal cells to modulation of splicing. As a significant percentage of all mammalian mRNAs undergo alternative splicing, we predict that mitochondrial failure will unbalance a vast number of isoform equilibriums, which would give an important contribution to neurodegeneration.

The metabotropic P2Y4 receptor participates in the commitment to differentiation and cell death of human neuroblastoma SH-SY5Y cells

Extracellular nucleotides exert a variety of biological actions through different subtypes of P2 receptors. Here we characterized in the human neuroblastoma SH-SY5Y cells the simultaneous presence of various P2 receptors, belonging to the P2X ionotropic and P2Y metabotropic families. Western blot analysis detected the P2X1,2,4,5,6,7 and P2Y1,2,4,6, but not the P2X3 and P2Y12 receptors. We then investigated which biological effects were mediated by the P2Y4 subtype and its physiological pyrimidine agonist UTP. We found that neuronal differentiation of the SH-SY5Y cells with dibutiryl-cAMP increased the expression of the P2Y4 protein and that UTP itself was able to positively interfere with neuritogenesis. Moreover, transient transfection and activation of P2Y4 also facilitated neuritogenesis in SH-SY5Y cells, as detected by morphological phase contrast analysis and confocal examination of neurofilament proteins NFL. This was concurrent with increased transcription of immediate-early genes linked to differentiation such as cdk-5 and NeuroD6, and activity of AP-1 transcription family members such as c-fos, fos-B, and jun-D. Nevertheless, a prolonged activation of the P2Y4 receptor by UTP also induced cell death, both in naive, differentiated, and P2Y4-transfected SH-SY5Y cells, as measured by direct count of intact nuclei and cytofluorimetric analysis of damaged DNA. Taken together, our data indicate that the high expression and activation of the P2Y4 receptor participates in the neuronal differentiation and commitment to death of SH-SY5Y cells.

Transcriptional Profiling of γδ T Cells Identifies a Role for Vitamin D in the Immunoregulation of the Vγ9Vδ2 Response to Phosphate-Containing Ligands

Vitamin D is a steroid hormone that, in addition to its well-characterized role in calcium/phosphate metabolism, has been found to have regulatory properties for immune system function. The nuclear vitamin D receptor is widely expressed in tissues, but has also been shown to be regulated by hormones, growth factors, and cytokines. In this study we show that activation of human Vdelta2Vgamma9 T cells by nonpeptidic monoalkyl phosphates such as isopentenyl pyrophosphate leads to the up-regulation of the vitamin D receptor via a pathway that involves the classical isoforms of protein kinase C. We further show that this receptor is active by demonstrating that the ligand 1alpha,25-dihydroxyvitamin D3 (vitD3) significantly inhibits in a dose-dependent fashion phospholigand-induced gammadelta T cell expansion, IFN-gamma production, and CD25 expression. We also show that vitD3 negatively regulates signaling via Akt and ERK and, at high concentrations, potentiates Ag-induced cell death. As such, these data provide further support for the immunoregulatory properties of vitamin D, and suggest that the ability of vitD3 to negatively regulate the proinflammatory activity of gammadelta T cells may contribute to the protection this vitamin affords against inflammatory and autoimmune disorders dependent upon Th1-type responses.

Apoptosome inactivation rescues proneural and neural cells from neurodegeneration

Deficiency of the apoptosome component Apaf1 leads to accumulation of supernumerary brain cells in mouse embryos. We observed that neural precursor cells (NPCs) in Apaf1(-/-) embryos escape programmed cell death, proliferate and retain their potential to differentiate. To evaluate the circumstances of Apaf1(-/-) NPC survival and investigate their fate under neurodegenerative conditions, we established cell lines of embryonic origin (ETNA). We found that Apaf1(-/-) NPCs resist common apoptotic stimuli and neurodegenerative inducers such as amyloid-beta peptide (typical of Alzheimer's disease) and mutant G93A superoxide dismutase 1 (typical of familial amyotrophic lateral sclerosis). Similar results were obtained in Apaf1(-/-) primary cells. When death is prevented by Apaf1 deficiency, cytochrome c is released from mitochondria and rapidly degraded by the proteasome, but mitochondria remain intact. Under these conditions, neither activation by cleavage of initiator caspases nor release of alternative apoptotic inducers from mitochondria takes place. In addition, NPCs can still differentiate, as revealed by neurite outgrowth and expression of differentiation markers. Our findings imply that the mitochondrion/apoptosome pathway is the main route of proneural and neural cells to death and that its inhibition prevents them from dismantling in neurodegenerative conditions. Indeed, the ETNA cell model is ideally suited for exploring the potential of novel cell therapies for the treatment of human neurodegenerations.

Homing and memory patterns of human γδ T cells in physiopathological situations

Vgamma9Vdelta2 are a heterogeneous population of T cells and comprise distinct naive, memory and effector populations that can be distinguished on the basis of surface marker expression and effector functions. We review here these recently studied features of Vgamma9Vdelta2 T lymphocyte biology and the roles they play in infectious and autoimmune diseases.

Role of the metabotropic P2Y(4) receptor during hypoglycemia: cross talk with the ionotropic NMDAR1 receptor

It is well established that both extracellular ATP and glutamate exert a critical role during metabolic impairment, that several P2 receptor subunits are directly involved in this action and that a strong relationship exists between glutamatergic and purinergic signals. Therefore, here we studied the molecular behavior of the purinergic metabotropic P2Y(4) and the glutamatergic ionotropic NMDAR1 receptors during hypoglycemic cell death. We find that these proteins are oppositely modulated during glucose starvation (P2Y(4) is induced, whereas NMDAR1 is inhibited) and that both P2 and NMDA antagonists can restore basal protein expression levels. Moreover, double immunofluorescence experiments with confocal laser microscopy reveal co-localization at the membrane level between the P2Y(4) and NMDAR1 receptors, in both homologous (cerebellar granule neurons) and heterologous (Hek-293) cellular systems. This is furthermore confirmed by co-immunoprecipitation experiments. Finally, when we express the P2Y(4) receptor in the heterologous SH-SY5Y neuronal cell line, hypoglycemia then causes severe cell death and simultaneous downregulation of the NMDAR1 protein. In summary, our work establishes a potential molecular interplay between P2Y(4) and NMDAR1 receptors during glucose deprivation and the causative role of the P2Y(4) during cell death.

FcγRIII discriminates between 2 subsets of Vγ9Vδ2 effector cells with different responses and activation pathways

Upon recognition of nonpeptidic phosphoantigens, human Vδ2 T lymphocytes enter a lineage differentiation pattern that determines the generation of memory cells with a range of effector functions. Here, we show that within the effector memory Vδ2 population, 2 distinct and complementary subsets with regard to phenotype, mode of activation, and type of responses can be identified: Vδ2 TEMh cells, which express high levels of chemokine receptors, but low levels of perforin and of natural killer receptors (NKRs) and which produce large amounts of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) in response to T-cell receptor (TCR)–specific stimulation by phosphoantigens; and Vδ2TEMRA cells, which constitutively express several NKRs, high amounts of perforin, but low levels of chemokine receptors and of IFN-γ. These NK-like cells are refractory to phosphoantigen but respond to activation via FcγRIII (CD16) and are highly active against tumoral target cells. Thus, circulating Vδ2T lymphocytes comprise 2 functionally diverse subsets of effector memory cells that may be discriminated on the basis of CD16 expression.

Cell death in amyotrophic lateral sclerosis: interplay between neuronal and glial cells

Mutations in the gene coding for the ubiquitous, anti-oxidant enzyme Cu,Zn superoxide dismutase (SOD1) are associated with familial amyotrophic lateral sclerosis (fALS), a fatal disease characterized by selective loss of motor neurons. Expression of a mutant SOD1 typical of fALS patients restricted to either motor neurons or astrocytes is insufficient to generate a pathological phenotype in mouse models, suggesting that a deleterious interplay between different cell types is necessary for the pathogenesis of the disease. In this study, we demonstrate the actual role of a functional cross-talk between glial and neuronal cells expressing fALS mutant G93A-SOD1, where an increase in the production of reactive oxygen species occurs. We show that human glioblastoma cells expressing G93A-SOD1 induce activation of caspase-1, release of cytokines, and activation of apoptotic pathways in cocultured human neuroblastoma cells also expressing G93A-SOD1. Activation of caspase-1 and caspase-3 is observed also in neuroblastoma lines expressing other fALS-SOD1s (G37R, G85R, and I113T) cocultured with glioblastoma lines expressing the corresponding mutant enzymes. These effects are consequent to activation of inflammatory processes in G93A-glioblastoma cells stimulated by cocultured G93A-neuroblastoma. Furthermore, selective death of embryonal spinal motor neurons from G93A-SOD1 transgenic mice is induced by coculture with G93A-glioblastoma and prevented by inhibition of NO synthase. Proinflammatory cytokines, interferon-gamma, and nitric oxide are among the molecular signals exchanged between glial and neuronal cells that generate a functional interplay between the two cell types. This cross-talk may be crucial for the pathogenesis of SOD1-linked fALS but also for the more common sporadic form of the disease, where markers of increased oxidative stress and of glial activation have been found.

2-ClATP exerts anti-tumoural actions not mediated by P2 receptors in neuronal and glial cell lines

We investigated the effects of the ATP analogue and P2 receptor agonist 2-ClATP on growth and survival of different neuronal (PC12, PC12nnr5 and SH-SY5Y) and glial (U87 and U373) cell lines, by the use of direct count of intact nuclei, fluorescence microscopy, fluorescence-activated cell sorter analysis (FACS) and high pressure liquid chromatography (HPLC). 2-ClATP lowered the number of cultured PC12nnr5, SH-SY5Y, U87 and U373 cells to almost 5%, and of PC12 cells to about 35% after 3-4 days of treatment. EC(50) was in the 5-25 microM range, with 2-ClATP behaving as a cytotoxic or cytostatic agent. Analysis of the biological mechanisms demonstrated that pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (P2 receptor antagonist and nucleotidases inhibitor), but not Caffeine or CGS-15493 (P1 receptor antagonists) effectively prevented 2-ClATP-induced toxicity. 2-ClATP metabolic products (2-ClADP, 2-ClAMP, 2-Cladenosine) and new synthesis derivatives (2-CldAMP, 2-Cldadenosine-3',5'-bisphosphate and 2-CldATP) exerted similar cytotoxic actions. Inhibition of both serum nucleotidases and purine nucleoside transporters strongly reduced 2-ClATP-induced cell death, which was conversely increased by the nucleotide hydrolyzing enzyme apyrase. The adenosine kinase inhibitor 5-iodotubericidin totally prevented 2-ClATP or 2-Cladenosine-induced toxicity. In summary, our findings indicate that 2-ClATP exerts either cell cycle arrest or cell death, acting neither on P2 nor on P1 receptors, but being extracellularly metabolized into 2-Cladenosine, intracellularly transported and re-phosphorylated.

Transendothelial migratory pathways of V delta 1+TCR gamma delta+ and V delta 2+TCR gamma delta+ T lymphocytes from healthy donors and multiple sclerosis patients: involvement of phosphatidylinositol 3 kinase and calcium calmodulin-dependent kinase II

We have previously reported that the Vdelta2(+)TCRgammadelta(+) T lymphocyte subset, expressing the NK receptor protein 1a (NKRP1a; CD161), is expanded in patients with relapsing-remitting multiple sclerosis and uses this molecule to migrate through endothelium. In this work, we show that Vdelta1(+) and Vdelta2(+) gammadelta T lymphocytes use distinct signal transduction pathways to accomplish this function. Indeed, we have found that Vdelta1(+) cells lack NKRP1a and selectively express the platelet endothelial cell adhesion molecule 1 (PECAM1; CD31), which drives transendothelial migration of this cell subset, at variance with Vdelta2(+) T cells, which are PECAM1 negative and use NKRP1a for transmigration. Interestingly, when Vdelta2(+) T cells were pretreated with two specific inhibitors of the calcium calmodulin-dependent kinase II KN62 and KN93, but not with the inactive compound KN92, the number of migrating cells and the rate of transmigration were significantly decreased. In turn, the phosphatidylinositol 3 kinase blockers wortmannin and LY294002 exerted a dose-dependent inhibition of Vdelta1(+) cell migration. Finally, NKRP1a and PECAM1 engagement led to activation of different signal transduction pathways: indeed, oligomerization of NKRP1a on Vdelta2(+) T cells activates calcium calmodulin-dependent kinase II, while occupancy of PECAM1 on Vdelta1(+) cells triggers the phosphatidylinositol 3 kinase-dependent Akt/protein kinase Balpha activation. These findings suggest that subsets of gammadelta T lymphocytes may migrate to the site of lesion in multiple sclerosis using two different signaling pathways to extravasate.