Cytopathology of Chondromyxoid Fibroma: Report of 2 Cases with Immunocytochemical Expression of GRM1.

INTRODUCTION: Chondromyxoid fibroma (CMF) is a rare, benign bone tumor that occurs predominantly in the second and third decades of life, more frequently in males. Overexpression of GRM1 as a consequence of tumor-specific gene rearrangement of GRM1 has recently been reported as a useful immunohistochemical marker for histopathological diagnosis of CMF. However, the usefulness of GRM1 staining of cytology specimens has not yet been evaluated. In this report, the cytological findings and GRM1 immunocytochemistry of two cases of CMF are described. CASE PRESENTATIONS: Case 1 was a 15-year-old girl with a rib tumor. Imaging findings suggested a benign neurogenic tumor such as schwannoma. The tumor had increased in size over a 2-year period and was resected. Case 2 was a 14-year-old boy with a metatarsal tumor involving his left first toe. Imaging findings were suspicious of a benign neoplastic lesion. Biopsy findings suggested a benign tumor, and the patient underwent tumor resection. Cytologically, in both cases the tumor cells were predominantly spindle-shaped or stellate, with a myxoid to chondromyxoid background matrix and multinucleated giant cells, and these matrices were metachromatic with Giemsa staining. Cellular atypia was more accentuated in case 2 than in case 1. Immunocytochemical staining for GRM1 was positive in both cases. CONCLUSION: Due to the overlap in cytological findings, it is often difficult to differentiate CMF from chondroblastoma and chondrosarcoma grade 2. Immunocytochemical staining for GRM1 may support the diagnosis of CMF, and the reuse of Papanicolaou-stained specimens is applicable. The present cases further demonstrated the difficulty of differentiating CMF from other mimicking tumors such as chondroblastoma and chondrosarcoma grade 2. In such instances, immunocytochemistry for GRM1 is applicable to the diagnostic process, the value of which is strengthened by reusing Papanicolaou-stained specimens.

MGluR7 is a presynaptic metabotropic glutamate receptor at ribbon synapses of inner hair cells.

Glutamate is the most pivotal excitatory neurotransmitter in the central nervous system. Metabotropic glutamate receptors (mGluRs) dimerize and can couple to inhibitory intracellular signal cascades, thereby protecting glutamatergic neurons from excessive excitation and cell death. MGluR7 is correlated with age-related hearing deficits and noise-induced hearing loss; however its exact localization in the cochlea is unknown. Here, we analyzed the expression and localization of mGluR7a and mGluR7b in mouse cochlear wholemounts in detail, using confocal microscopy and 3D reconstructions. We observed a presynaptic localization of mGluR7a at inner hair cells (IHCs), close to the synaptic ribbon. To detect mGluR7b, newly generated antibodies were characterized and showed co-localization with mGluR7a at IHC ribbon synapses. Compared to the number of synaptic ribbons, the numbers of mGluR7a and mGluR7b puncta were reduced at higher frequencies (48 to 64 kHz) and in older animals (6 and 12 months). Previously, we reported a presynaptic localization of mGluR4 and mGluR8b at this synapse type. This enables the possibility for the formation of homo- and/or heterodimeric receptors composed of mGluR4, mGluR7a, mGluR7b and mGluR8b at IHC ribbon synapses. These receptor complexes might represent new molecular targets suited for pharmacological concepts to protect the cochlea against noxious stimuli and excitotoxicity.

Clinical features, prognostic factors, and antibody effects in anti-mGluR1 encephalitis.

OBJECTIVE: To clinically characterize patients with anti-metabotropic glutamate receptor (mGluR) 1 encephalitis, to identify prognostic factors, and to study the immunoglobulin G (IgG) subclasses and effects of antibodies on neuronal mGluR1 clusters. METHODS: Clinical information on new and previously reported patients was reviewed. Antibodies to mGluR1 and IgG subclasses were determined with brain immunohistochemistry and cell-based assays, and their effects on mGluR1 clusters were studied on rat hippocampal neurons. RESULTS: Eleven new patients were identified (10 adults, 1 child);4 were female. In these and 19 previously reported cases (n = 30, median age 55 years), the main clinical manifestation was a subacute cerebellar syndrome that in 25 (86%) patients was associated with behavioral/cognitive changes or other neurologic symptoms. A tumor was found in 3 of 26 (11%). Brain MRI was abnormal in 7 of 19 (37%) at onset and showed cerebellar atrophy in 10 of 12 (83%) at follow-up. Twenty-five of 30 (83%) patients received immunotherapy. Follow-up was available for 25: 13 (52%) had clinical stabilization; 10 (40%) showed significant improvement; and 2 died. At the peak of the disease, patients with bad outcome at 2 years (modified Rankin Scale score > 2, n = 7) were more likely to have higher degree of initial disability, as reflected by a worse Scale for Assessment and Rating of Ataxia score, and more frequent need of assistance to walk. Antibodies to mGluR1 were mainly IgG1 and caused a significant decrease of mGluR1 clusters in cultured neurons. CONCLUSIONS: Anti-mGluR1 encephalitis manifests as a severe cerebellar syndrome, often resulting in long-term disability and cerebellar atrophy. The antibodies are pathogenic and cause significant decrease of mGluR1 clusters in cultured neurons.

Antibodies against metabotropic glutamate receptor type 1 in a toddler with acute cerebellitis.

Antibodies against metabotropic glutamate receptor type 1 (mGluR1) have been described in adults with paraneoplastic or non-paraneoplastic subacute cerebellitis. Patients responded to immunotherapy depending on disease duration. Here, we report on a 3 years 2 months old male toddler with acute onset ataxia and mGluR1 antibodies in serum and cerebrospinal fluid (CSF). He was started on prednisolone 4 weeks after disease onset and remitted largely within half a year.

Paraneoplastic cerebellar ataxia and antibodies to metabotropic glutamate receptor 2.

OBJECTIVE: To report the presence of a new neuronal surface antibody against the metabotropic glutamate receptor 2 antibody (mGluR2-Ab) in 2 patients with paraneoplastic cerebellar ataxia. METHODS: mGluR2-Abs were initially characterized by immunohistochemistry on the rat brain and confirmed by immunofluorescence on HEK293 cells transfected with mGluR2. Additional studies included analysis of potential cross-reactivity with other mGluRs, expression of mGluR2 in patients' tumors, and the effects of mGluR2-Abs on cultures of rat hippocampal neurons. RESULTS: Patient 1 was a 78-year-old woman with progressive cerebellar ataxia with an initial relapsing-remitting course who developed a small-cell tumor of unknown origin. Patient 2 was a 3-year-old girl who presented a steroid-responsive acute cerebellitis preceding the diagnosis of an alveolar rhabdomyosarcoma. Patients' serum and CSF showed a characteristic immunostaining of the hippocampus and cerebellum in rat brain sections and immunolabeled the cell surface of live rat hippocampal neurons. HEK293 cells transfected with mGluR1, 2, 3, and 5 confirmed that patients' antibodies only recognized mGluR2. mGluR2-Abs were not detected in 160 controls, 120 with paraneoplastic, autoimmune, or degenerative ataxias, and 40 with autoimmune encephalitis and antibodies against mGluR5 or unknown antigens. Expression of mGluR2 in tumors was confirmed by immunohistochemistry using a commercial mGluR2-Ab. Incubation of live rat hippocampal neurons with CSF of patient 2 did not modify the density of surface mGluR2 clusters. CONCLUSIONS: mGluR2-Abs are a novel biomarker of paraneoplastic cerebellar ataxia. The potential pathogenic effect of the antibodies is not mediated by downregulation or internalization of neuronal surface mGluR2.

Disturbance of Metabotropic Glutamate Receptor-Mediated Long-Term Depression (mGlu-LTD) of Excitatory Synaptic Transmission in the Rat Hippocampus After Prenatal Immune Challenge.

Maternal immune challenge has proved to induce moderate to severe behavioral disabilities in the offspring. Cognitive/behavioral deficits are supported by changes in synaptic plasticity in different brain areas. We have reported previously that prenatal exposure to bacterial LPS could induce inhibition of hippocampal long-term potentiation (LTP) in the CA1 area of the juvenile/adult male offspring associated with spatial learning inabilities. Nevertheless, deficits in plasticity could be observed at earlier stages as shown by the early loss of long-term depression (LTD) in immature animals. Moreover, aberrant forms of plasticity were also evidenced such as the transient occurrence of LTP instead of LTD in 15-25 day-old animals. This switch from LTD to LTP seemed to involve the activation of metabotropic glutamate receptor subtype 1 and 5 (mGlu1/5). We have thus investigated here whether the long-term depression elicited by the direct activation of these receptors (mGlu-LTD) with a selective agonist was also disturbed after prenatal stress. We find that in prenatally stressed rats, mGlu1/5 stimulation elicits long-term potentiation (mGlu-LTP) independently of N-methyl-D-aspartate receptors. Both mGlu5 and mGlu1 receptors are involved in this switch of plasticity. Moreover, this mGlu-LTP is still observed at later developmental stages than previously reported, i.e. after 25 day-old. In addition, increasing synaptic GABA with tiagabine tends to inhibit mGlu-LTP occurrence. By contrast, long-term depression induced with the activation of CB1 cannabinoid receptor is unaffected by prenatal stress. Therefore, prenatal stress drastically alters mGlu1/5-associated plasticity throughout development. MGlu-mediated plasticity is an interesting parameter to probe the long-lasting deficits reported in this model.

Long-term clinical follow-up of a patient with non-paraneoplastic cerebellar ataxia associated with anti-mGluR1 autoantibodies.

The clinical features of cerebellar ataxia associated with anti-metabotropic glutamate receptor 1 (mGluR1) autoantibodies, a rare autoimmune-mediated cerebellar ataxia, remain to be elucidated. Here, we describe a patient with non-paraneoplastic cerebellar ataxia associated with anti-mGluR1 autoantibodies, who was followed up over 5 years. She presented with relapses and remissions of subacute progressive cerebellar ataxia that were responsive to immunotherapy. Although serum anti-mGluR1 autoantibodies were continuously detected and cerebellar atrophy gradually progressed, repeated intravenous immunoglobulin therapy and oral immunosuppressants ensured cerebellar ataxia remained at almost the same level during the observation period.

Control of autoimmune inflammation using liposomes to deliver positive allosteric modulators of metabotropic glutamate receptors.

Multiple sclerosis (MS) is an autoimmune disease where myelin is incorrectly recognized as foreign and attacked by the adaptive immune system. Dendritic cells (DCs) direct adaptive immunity by presenting antigens to T cells, therefore serving as a target for autoimmune therapies. N-Phenyl-7-(hydroxyimino) cyclopropa[b]chromen-1a-carboxamide (PHCCC), a positive allosteric modulator of metabotropic glutamate receptor 4 (mGluR4), can promote regulatory T cells by altering cytokine secretion to bias T cell differentiation. The therapeutic potential of PHCCC, however, is hindered by dose-limiting toxicity, poor solubility, and the need for frequent dosing. We hypothesized liposomal delivery of PHCCC might enable safe, effective delivery of this hydrophobic drug to exploit metabolism as a means of controlling inflammation in self-reactive immune cells. PHCCC was readily encapsulated in liposomes modified with polyethylene glycol. Under sink conditions, controlled release resulted in 58% of drug released into media over 18 hours. Culture of primary DCs with PHCCC liposomes reduced pro-inflammatory cytokine secretion while reducing toxicity four-fold compared with soluble PHCCC. During co-culture of DCs with myelin-reactive T cells from transgenic mice, PHCCC liposomes reduced T cell proliferation and interferon gamma secretion. These results support the potential of using liposomes to promote tolerance through biocompatible delivery of metabolic modulators. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2977-2985, 2017.

CNS syndromes associated with antibodies against metabotropic receptors.

PURPOSE OF REVIEW: Autoantibodies to Central nervous system (CNS) metabotropic receptors are associated with a growing family of autoimmune brain diseases, including encephalitis, basal ganglia encephalitis, Ophelia syndrome, and cerebellitis. The purpose of this review is to summarize the state of knowledge regarding the target receptors, the neurological autoimmune disorders, and the pathogenic mechanisms. RECENT FINDINGS: Antibodies to the γ-aminobutyric acid B receptor are associate with limbic encephalitis and severe seizures, often with small cell lung cancers. Metabotropic glutamate receptor 5 (mGluR5) antibodies associate with Ophelia syndrome, a relatively mild form of encephalitis linked to Hodgkin lymphoma. mGluR1 antibodies associate with a form of cerebellar degeneration, and also Hodgkin lymphoma. Antibodies to Homer 3, a protein associated with mGluR1, have also been reported in two patients with cerebellar syndromes. Dopamine-2 receptor antibodies have been reported by one group in children with basal ganglia encephalitis and other disorders. SUMMARY: CNS metabotropic receptor antibodies may exert direct inhibitory effects on their target receptors, but the evidence is more limited than with autoantibodies to ionotropic glutamate receptors. In the future, improved recognition of these patients may lead to better outcomes. Understanding the molecular mechanisms of the diseases may uncover novel treatment strategies.

Metabotropic glutamate receptor 3 (mGlu3; mGluR3; GRM3) in schizophrenia: Antibody characterisation and a semi-quantitative western blot study.

BACKGROUND: Metabotropic glutamate receptor 3 (mGlu3, mGluR3), encoded by GRM3, is a risk gene for schizophrenia and a therapeutic target. It is unclear whether expression of the receptor is altered in the disorder or related to GRM3 risk genotype. Antibodies used to date to assess mGlu3 in schizophrenia have not been well validated. OBJECTIVE: To characterise six commercially available anti-mGlu3 antibodies for use in human brain, and then conduct a semi-quantitative study of mGlu3 immunoreactivity in schizophrenia. METHODS: Antibodies tested using Grm3-/- and Grm2-/-/3-/- mice and transfected HEK293T/17 cells. Western blotting on membrane protein isolated from superior temporal cortex of 70 patients with schizophrenia and 87 healthy comparison subjects, genotyped for GRM3 SNP rs10234440. RESULTS: One (out of six) anti-mGlu3 antibodies was fully validated, a C-terminal antibody which detected monomeric (~100kDa) and dimeric (~200kDa) mGlu3. A second, N-terminal, antibody detected the 200kDa band but also produced non-specific bands. Using the C-terminal antibody for western blotting in human brain, mGlu3 immunoreactivity was found to decline with age, and was affected by pH and post mortem interval. There were no differences in monomeric or dimeric mGlu3 immunoreactivity in schizophrenia or in relation to GRM3 genotype. The antibody was not suitable for immunohistochemistry. INTERPRETATION: These data highlight the value of knockout mouse tissue for antibody validation, and the need for careful antibody characterisation. The schizophrenia data show that involvement of GRM3 in the disorder and its genetic risk architecture is not reflected in total membrane mGlu3 immunoreactivity in superior temporal cortex.

Neuronal central nervous system syndromes probably mediated by autoantibodies.

In the last few years, a rapidly growing number of autoantibodies targeting neuronal cell-surface antigens have been identified in patients presenting with neurological symptoms. Targeted antigens include ionotropic receptors such as N-methyl-d-aspartate receptor or the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, metabotropic receptors such as mGluR1 and mGluR5, and other synaptic proteins, some of them belonging to the voltage-gated potassium channel complex. Importantly, the cell-surface location of these antigens makes them vulnerable to direct antibody-mediated modulation. Some of these autoantibodies, generally targeting ionotropic channels or their partner proteins, define clinical syndromes resembling models of pharmacological or genetic disruption of the corresponding antigen, suggesting a direct pathogenic role of the associated autoantibodies. Moreover, the associated neurological symptoms are usually immunotherapy-responsive, further arguing for a pathogenic effect of the antibodies. Some studies have shown that some patients' antibodies may have structural and functional in vitro effects on the targeted antigens. Definite proof of the pathogenicity of these autoantibodies has been obtained for just a few through passive transfer experiments in animal models. In this review we present existing and converging evidence suggesting a pathogenic role of some autoantibodies directed against neuronal cell-surface antigens observed in patients with central nervous system disorders. We describe the main clinical symptoms characterizing the patients and discuss conflicting arguments regarding the pathogenicity of these antibodies.

Metabotropic glutamate receptor type 1 autoimmunity: Clinical features and treatment outcomes.

OBJECTIVE: To describe retrospectively the clinical associations of immunoglobulin G (IgG) targeting metabotropic glutamate receptor 1 (mGluR1-IgG). METHODS: Specimens of 9 patients evaluated on a service basis in the Mayo Clinic Neuroimmunology Laboratory by tissue-based immunofluorescence assay (IFA) yielded a robust, synaptic immunostaining pattern consistent with mGluR1-IgG (serum, 9; CSF, 2 available). Transfected HEK293 cell-based assay (CBA) confirmed mGluR1 specificity in all 11 specimens. A further 2 patients were detected in Germany primarily by CBA. RESULTS: The median symptom onset age for the 11 patients was 58 years (range 33-81 years); 6 were male. All 9 Mayo Clinic patients had subacute onset of cerebellar ataxia, 4 had dysgeusia, 1 had psychiatric symptoms, and 1 had cognitive impairment. All were evaluated for malignancy, but only 1 was affected (cutaneous T-cell lymphoma). One developed ataxia post-herpes zoster infection. Head MRIs were generally atrophic or normal-appearing, and CSF was inflammatory in just 1 of 5 tested, though mGluR1-IgG was detected in both specimens submitted. Five patients improved (attributable to immunotherapy in 4, spontaneously in 1), 3 stabilized (attributable to immunotherapy in 2, cancer therapy in 1), and 1 progressively declined (untreated). The 2 German patients had ataxia, but fulfilled multiple sclerosis diagnostic criteria (1 relapsing-remitting, 1 progressive). However, both had histories of hematologic malignancy (acute lymphocytic leukemia and mantle cell lymphoma), and had mGluR1-IgG detected in serum by CBA (weakly positive on tissue-based IFA). CONCLUSIONS: mGluR1 autoimmunity represents a treatable form of cerebellar ataxia. Dysgeusia may be a diagnostic clue. Paraneoplastic, parainfectious, or idiopathic causes may occur.

'Medusa-head ataxia': the expanding spectrum of Purkinje cell antibodies in autoimmune cerebellar ataxia. Part 1: Anti-mGluR1, anti-Homer-3, anti-Sj/ITPR1 and anti-CARP VIII.

Serological testing for anti-neural autoantibodies is important in patients presenting with idiopathic cerebellar ataxia, since these autoantibodies may indicate cancer, determine treatment and predict prognosis. While some of them target nuclear antigens present in all or most CNS neurons (e.g. anti-Hu, anti-Ri), others more specifically target antigens present in the cytoplasm or plasma membrane of Purkinje cells (PC). In this series of articles, we provide a detailed review of the clinical and paraclinical features, oncological, therapeutic and prognostic implications, pathogenetic relevance, and differential laboratory diagnosis of the 12 most common PC autoantibodies (often referred to as 'Medusa-head antibodies' due to their characteristic somatodendritic binding pattern when tested by immunohistochemistry). To assist immunologists and neurologists in diagnosing these disorders, typical high-resolution immunohistochemical images of all 12 reactivities are presented, diagnostic pitfalls discussed and all currently available assays reviewed. Of note, most of these antibodies target antigens involved in the mGluR1/calcium pathway essential for PC function and survival. Many of the antigens also play a role in spinocerebellar ataxia. Part 1 focuses on anti-metabotropic glutamate receptor 1-, anti-Homer protein homolog 3-, anti-Sj/inositol 1,4,5-trisphosphate receptor- and anti-carbonic anhydrase-related protein VIII-associated autoimmune cerebellar ataxia (ACA); part 2 covers anti-protein kinase C gamma-, anti-glutamate receptor delta-2-, anti-Ca/RhoGTPase-activating protein 26- and anti-voltage-gated calcium channel-associated ACA; and part 3 reviews the current knowledge on anti-Tr/delta notch-like epidermal growth factor-related receptor-, anti-Nb/AP3B2-, anti-Yo/cerebellar degeneration-related protein 2- and Purkinje cell antibody 2-associated ACA, discusses differential diagnostic aspects and provides a summary and outlook.

Ligation of metabotropic glutamate receptor 3 (Grm3) ameliorates lupus-like disease by reducing B cells.

Recently B-cell activating factor (BAFF) was identified by our group and others as a novel therapeutic target for the treatment of autoimmune diseases. To expand upon this, we utilized microarrays to screen for molecules upregulated in B cells from BAFF-inhibited mice with lupus-like disease and identified metabotropic glutamate receptor 3 (Grm3). In addition to confirming the expression of this receptor in B cells, a synthetic agonist of Grm3 was found to downregulate B cells and ameliorate autoimmune symptoms in mice. Conversely, a Grm3 antagonist increased B-cell numbers and further aggravated disease. Thus, these results suggest that activation of Grm3 ameliorates lupus-like disease in mice by reducing B cell numbers. Not only do the findings presented in this study increase our understanding of the inhibitory signals initiated on the surface of B cells, but they also identify a novel potential target for the treatment of autoimmune diseases.

Glutamate secretion and metabotropic glutamate receptor 1 expression during Kaposi's sarcoma-associated herpesvirus infection promotes cell proliferation.

Kaposi's sarcoma associated herpesvirus (KSHV) is etiologically associated with endothelial Kaposi's sarcoma (KS) and B-cell proliferative primary effusion lymphoma (PEL), common malignancies seen in immunocompromised HIV-1 infected patients. The progression of these cancers occurs by the proliferation of cells latently infected with KSHV, which is highly dependent on autocrine and paracrine factors secreted from the infected cells. Glutamate and glutamate receptors have emerged as key regulators of intracellular signaling pathways and cell proliferation. However, whether they play any role in the pathological changes associated with virus induced oncogenesis is not known. Here, we report the first systematic study of the role of glutamate and its metabotropic glutamate receptor 1 (mGluR1) in KSHV infected cell proliferation. Our studies show increased glutamate secretion and glutaminase expression during de novo KSHV infection of endothelial cells as well as in KSHV latently infected endothelial and B-cells. Increased mGluR1 expression was detected in KSHV infected KS and PEL tissue sections. Increased c-Myc and glutaminase expression in the infected cells was mediated by KSHV latency associated nuclear antigen 1 (LANA-1). In addition, mGluR1 expression regulating host RE-1 silencing transcription factor/neuron restrictive silencer factor (REST/NRSF) was retained in the cytoplasm of infected cells. KSHV latent protein Kaposin A was also involved in the over expression of mGluR1 by interacting with REST in the cytoplasm of infected cells and by regulating the phosphorylation of REST and interaction with ß-TRCP for ubiquitination. Colocalization of Kaposin A with REST was also observed in KS and PEL tissue samples. KSHV infected cell proliferation was significantly inhibited by glutamate release inhibitor and mGluR1 antagonists. These studies demonstrated that elevated glutamate secretion and mGluR1 expression play a role in KSHV induced cell proliferation and suggest that targeting glutamate and mGluR1 is an attractive therapeutic strategy to effectively control the KSHV associated malignancies.

Patient with homer-3 antibodies and cerebellitis.

IMPORTANCE: Homer proteins are a family of scaffolding proteins of the postsynaptic density. Homer-3 colocalizes and modulates the activity of group I metabotropic glutamate receptors (mGluR1 and mGluR5). Cerebellitis has been reported in association with antibodies to mGluR1. We describe the second patient with cerebellitis and Homer-3 antibodies and report a novel, highly specific immunoblot assay. OBSERVATIONS: A 38-year-old man had acute onset of headache, nausea, vomiting, and confusion. He developed a pancerebellar syndrome during the ensuing week. Extensive studies did not reveal any tumor. Cerebrospinal fluid analysis showed a white blood cell count of 60/µL (to convert to ×109 per liter, multiply by 0.001). Brain magnetic resonance imaging findings were normal. For 2 years, the patient was treated with intravenous immunoglobulins and steroids, with partial improvement of the cerebellar ataxia. The patient was negative for onconeural (Hu, Yo, Ri, CV2, Tr, amphiphysin, and Ma2), glutamic acid decarboxylase, and mGluR1 antibodies. Immunohistochemistry on rat brain revealed immunostaining of the cerebellar molecular layer. Homer-3 antibodies were demonstrated by immunoblot of recombinant Homer-3. The clinical features of this patient and a previously described patient with Homer-3 antibodies are similar to those of patients with mGluR1 antibodies. CONCLUSIONS AND RELEVANCE: We report the second case of autoimmune cerebellar ataxia associated with Homer-3 antibodies. The presence of Homer-3 autoantibodies should be considered in the differential diagnosis of patients with subacute cerebellar ataxia of unknown cause.

Glutamate induces neutrophil cell migration by activating class I metabotropic glutamate receptors.

Leukocytes are recruited at the site of infection or injury as a part of the innate immune system, and play a very critical role in fighting the invading microorganisms and/or healing wounds. Neutrophils are the most abundant leukocytes in healthy humans and are the principal cell types that arrive at the target site in the initial phase of this process. Previous studies from our laboratory have shown that the amino acid glutamate is a novel chemotaxis-inducing factor for human neutrophils. In this report, we provide evidences that clearly demonstrate that the glutamate-induced neutrophil cell migration activity is mediated by the class I metabotropic glutamate receptors. Our results further show that a specific integrin ß2 (ITG ß2) receptor, namely LFA1 (α(L)ß(2)) is activated upon glutamate treatment and is required for further downstream signaling events leading to increased migration of human neutrophil cells. Following glutamate stimulation, LFA1 is phosphorylated by the Src Kinase Lck at the Y735 residue, which triggers a downstream signaling cascade leading to activation of PI3K, Syk, Vav and finally the Rho family GTPase, Rac2. Interestingly, glutamate was previously found to be present in elevated levels in wound fluid. Furthermore, glutamate level was also found to go up following inflammation. Taken together, our study suggests a novel mode of neutrophil recruitment to the target site following an infection or injury.