In vitro effects of wound-dressings on key wound healing properties of dermal fibroblasts.

Healing of complex wounds requires dressings that must, at least, not hinder and should ideally promote the activity of key healing cells, in particular fibroblasts. This in vitro study assessed the effects of three wound-dressings (a pure Ca2+ alginate: Algostéril®, a Ca2+ alginate + carboxymethylcellulose: Biatain alginate® and a polyacrylate impregnated with lipido-colloid matrix: UrgoClean®) on dermal fibroblast activity. The results showed the pure calcium alginate to be non-cytotoxic, whereas the other wound-dressings showed moderate to strong cytotoxicity. The two alginates stimulated fibroblast migration and proliferation, whereas the polyacrylate altered migration and had no effect on proliferation. The pure Ca2+ alginate significantly increased the TGF-ß-induced fibroblast activation, which is essential to healing. This activation was confirmed by a significant increase in Vascular endothelial growth factor (VEGF) secretion and a higher collagen production. The other dressings reduced these fibroblast activities. The pure Ca2+ alginate was also able to counteract the inhibitory effect of NK cell supernatants on fibroblast migration. These in vitro results demonstrate that tested wound-dressings are not equivalent for fibroblast activation. Only Algostéril was found to promote all the fibroblast activities tested, which could contribute to its healing efficacy demonstrated in the clinic.

The value of five blood markers in differentiating mycosis fungoides and Sézary syndrome: a validation cohort.

BACKGROUND: Clinical and histological diagnosis of Sézary syndrome (SS) and mycosis fungoides (MF) is challenging in clinical routine. OBJECTIVES: We investigated five blood markers previously described for SS (T-plastin, Twist, KIR3DL2, NKp46 and Tox) in a prospective validation cohort of patients. METHODS: We included 447 patients in this study and 107 patients were followed up for prognosis. The markers were analysed by reverse transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) on peripheral blood leucocytes and CD4+ T cells in a cohort of consecutive patients with early MF, erythrodermic MF and SS and compared with patients presenting with benign inflammatory dermatoses (BID) and erythrodermic BID. The markers were assessed in parallel to gold standard values such as CD4/CD8 ratio, loss of CD7 and CD26 membrane expression and CD4 absolute values. Sensitivity and specificity were analysed by receiver operator characteristic curves. The prognostic value of selected markers was analysed on a subset of patients. This study was conducted in one centre. RESULTS: We defined cut-off values for each marker. T-plastin, Twist and KIR3DL2 had the best validity. SS may be overrepresented. The combination of T-plastin and Twist was able to differentiate between erythrodermic MF or BID and SS. The additional analysis of KIR3DL2 may be useful to predict the prognosis. CONCLUSIONS: We propose T-plastin, Twist and KIR3DL2 measured by RT-qPCR as new diagnostic markers for Sézary syndrome.

Revisiting the initial diagnosis and blood staging of mycosis fungoides and Sézary syndrome with the KIR3DL2 marker.

BACKGROUND: The early diagnosis of Sézary syndrome (SS) is challenging. Loss of CD7 and CD26 expression on CD4+ T cells is the currently used criterion in the initial diagnosis and staging of patients with SS. OBJECTIVES: Our aim was to evaluate the respective value of CD26, CD7 and KIR3DL2 expression on CD4+ T cells and total lymphocytes at initial diagnosis of SS. METHODS: This prospective study included 254 patients with clinical features consistent with cutaneous T-cell lymphoma seen at our institution between March 2014 and February 2019. Peripheral blood analysis by flow cytometry was performed for each patient at the time of diagnosis and during follow-up. The diagnosis of SS was based on ISCL/EORTC criteria. RESULTS: The presence of KIR3DL2+ Sézary cells (SCs) ≥ 200 µL-1 correlated with the diagnosis of SS, with sensitivity of 88·6% and specificity of 96·3%. All 154 patients with either inflammatory skin disease or other haematological disease had KIR3DL2+ cells < 200 µL-1 , while eight of them had CD4+ CD26- T cells ≥ 1000 µL-1 . Of five patients with SS and lymphopenia, four had CD4+ CD7- T cells < 1000 µL-1 and three had CD4+ CD26- T cells < 1000 µL-1 . However, all of them had KIR3DL2+ CD4+ T cells ≥ 200 µL-1 . Among patients with available samples during evolution, all B1-staged patients with ≥ 200 µL-1 KIR3DL2+ SCs at diagnosis evolved to B2 stage within 7 months. CONCLUSIONS: KIR3DL2 expression on T cells is highly specific and helps the early diagnosis of SS, especially in those patients with lymphopenia. What's already known about this topic? In the ISCL/EORTC cutaneous T-cell lymphoma (CTCL) categorization of blood involvement (B0-B2), B2 is defined as a T-cell receptor clonal rearrangement in blood, associated with high blood-smear Sézary cell (SC) count. Flow cytometry was developed to circumvent interobserver variability of SC manual counts; however, it mostly relies on detection of cells lacking CD7 and/or CD26 expression. We previously reported the reliability of KIR3DL2 as the first positive SC marker. What does this study add? Based on our analysis of 254 patients, we propose that KIR3DL2 be added to the ISCL/EORTC criteria for initial diagnosis of Sézary syndrome (SS) and B2 staging. This marker improved sensitivity of SS B2-stage CTCL diagnosis with a specificity > 95%, especially for patients with lymphopenia. We found KIR3DL2 helped early diagnosis of SS and was more reliable than CD26 in assessing blood tumour burden during therapy. What is the translational message? SC quantification is the major means of staging at initial diagnosis and monitoring blood tumour burden in a clinical trials setting. We recommend using a threshold value of KIR3DL2+ SCs ≥ 200 µL-1 or KIR3DL2+ SCs/lymphocytes ≥ 10% in the diagnostic criteria of SS and propose a novel algorithm for CTCL B2 blood staging.

Cutaneous presentation of adult T-cell leukemia/lymphoma (ATLL). Single-center study on 37 patients in metropolitan France between 1996 and 2016.

INTRODUCTION: Adult T-cell leukemia/lymphoma (ATLL) is a hematological malignancy associated with chronic HTLV-1 infection. AIM: To describe skin lesions in ATLL. METHODS: A descriptive, retrospective study between 1996 and 2016, including all patients diagnosed with ATLL at Saint-Louis Hospital (Paris, France). RESULTS: Thirty-seven ATLL patients were included. Fifteen patients (41%) had a cutaneous localization of the disease, which was present from the beginning of the disease for two thirds of them. ATLL types in patients with cutaneous localization of the disease were as follows: lymphoma, n=5, chronic, n=4, smoldering, n=4, acute, n=2. Half the patients had 2 or more cutaneous manifestations. The cutaneous localizations observed were as follows: nodulotumoral (n=8), plaques (n=7), multipapular (n=6), macular (n=4), purpuric (n=2). Among the 15 patients with cutaneous localization, median overall survival was significantly shorter in the acute and lymphoma types compared to the smoldering and chronic types (8.7 months vs. 79 months, P=0.003). DISCUSSION: ATLL is a hematologic malignancy with variable expression that is diagnosed only very rarely in metropolitan France, but that should be sought in patients from countries with high HTLV-1 prevalence in the event of a chronic eruption with patches, papules, plaques and/or tumors. The chronic and smoldering types are relatively indolent, whereas the acute and lymphoma forms have a poor prognosis.

Study of gene expression alteration in male androgenetic alopecia: evidence of predominant molecular signalling pathways.

BACKGROUND: Male androgenetic alopecia (AGA) is the most common form of hair loss in men. It is characterized by a distinct pattern of progressive hair loss starting from the frontal area and the vertex of the scalp. Although several genetic risk loci have been identified, relevant genes for AGA remain to be defined. OBJECTIVES: To identify biomarkers associated with AGA. METHODS: Molecular biomarkers associated with premature AGA were identified through gene expression analysis using cDNA generated from scalp vertex biopsies of hairless or bald men with premature AGA, and healthy volunteers. RESULTS: This monocentric study reveals that genes encoding mast cell granule enzymes, inflammatory mediators and immunoglobulin-associated immune mediators were significantly overexpressed in AGA. In contrast, underexpressed genes appear to be associated with the Wnt/ß-catenin and bone morphogenic protein/transforming growth factor-ß signalling pathways. Although involvement of these pathways in hair follicle regeneration is well described, functional interpretation of the transcriptomic data highlights different events that account for their inhibition. In particular, one of these events depends on the dysregulated expression of proopiomelanocortin, as confirmed by polymerase chain reaction and immunohistochemistry. In addition, lower expression of CYP27B1 in patients with AGA supports the notion that changes in vitamin D metabolism contributes to hair loss. CONCLUSIONS: This study provides compelling evidence for distinct molecular events contributing to alopecia that may pave the way for new therapeutic approaches.

KIR3DL2 (CD158k) is a potential therapeutic target in primary cutaneous anaplastic large-cell lymphoma.

BACKGROUND: KIR3DL2, an inhibitory receptor expressed by natural killer cells and a subset of normal CD8(+) T cells, is aberrantly expressed in neoplastic cells in transformed mycosis fungoides and Sézary syndrome. Anti-KIR3DL2 targeted antibody therapy has shown potent activity in preclinical models for these diseases. OBJECTIVES: To examine the expression of KIR3DL2 and its potential use as a therapeutic target in patients with primary cutaneous anaplastic large-cell lymphoma (pcALCL), the most aggressive cutaneous CD30(+) lymphoproliferative disease. METHODS: Samples from 11 patients with pcALCL and three CD30(+) lymphoproliferative disease cell lines - Mac1, Mac2a and Mac2b - were used in KIR3DL2 expression studies using immunohistochemistry, flow cytometry and reverse-transcriptase quantitative polymerase chain reaction. The effect of IPH4102, a monoclonal humanized IgG1 targeting KIR3DL2, was assessed by in vitro cytotoxicity assays against Mac1, Mac2a and Mac2b using allogeneic peripheral blood mononuclear cells as effectors. RESULTS: KIR3DL2 mRNA and protein were found in all human samples of pcALCL, and in the Mac2a and Mac2b cell lines. KIR3DL2 protein expression was present on 85·8 ± 14·0% of CD30(+) skin-infiltrating tumour cells. In vitro functional studies showed that KIR3DL2(+) Mac2a and Mac2b pcALCL lines are sensitive to antibody-derived cytotoxicity mediated by IPH4102, through activation of natural killer cells, in a concentration-dependent manner. CONCLUSIONS: pcALCL tumour cells express KIR3DL2, and we provide preclinical proof of concept for the use of IPH4102, a humanized anti-KIR3DL2 antibody, to treat patients with primary cutaneous CD30(+) ALCL.

Long-term efficacy and safety of alemtuzumab in advanced primary cutaneous T-cell lymphomas.

BACKGROUND: Alemtuzumab has been proposed as salvage therapy for refractory cutaneous T-cell lymphomas (CTCLs). Long-term follow-up data are scarce. OBJECTIVES: To assess the efficacy and safety of alemtuzumab in the treatment of advanced CTCL. METHODS: A multicentre retrospective analysis was carried out of 39 patients with advanced CTCL treated with alemtuzumab between 2003 and 2013. RESULTS: Thirty-nine patients (median age 62 years, range 20-83) with Sézary syndrome (SS, n = 23) or advanced mycosis fungoides (MF, n = 16) received alemtuzumab 30 mg two to three times per week for a median duration of 12 weeks (range 1-35). Fifteen patients received maintenance therapy for a median duration of 24 weeks (range 6-277). Eleven patients (28%) had transformed disease (MF, n = 10; SS, n = 1). After a median follow-up of 24 months (range 0.3-124), eight patients (21%) were still alive. The overall response rate was 51% in the whole study group (partial response, n = 13; complete response, n = 7); 70% in patients with SS and 25% in patients with MF (P = 0.009). The median time to progression was 3.4 months (range 0.4-42). Six patients (15%; SS, n = 5; MF, n = 1) remained progression free for > 2 years (median 56 months, range 28-117). Five patients experienced cutaneous large T-cell transformation during alemtuzumab treatment and one patient developed primary cutaneous large B-cell lymphoma. Twenty-four patients (62%) had a grade three or higher infectious adverse event and 10 (26%) a haematological toxicity, which led to treatment discontinuation in 17 cases (44%) and death in two (5%). CONCLUSIONS: Alemtuzumab may induce long-term remission in SS but seems ineffective in MF and transformed CTCL.

Poor relevance of a lymphocyte proliferation assay in lamotrigine-induced Stevens-Johnson syndrome or toxic epidermal necrolysis.

BACKGROUND: Prior use of 'lymphocyte transformation test' (LTT) in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) provided conflicting results, possibly dependent on sampling dates (acute vs. late). OBJECTIVE: Evaluation of LTT in patients with SJS or TEN who reacted to lamotrigine (LTG). In a small subgroup we explored the possible role of regulatory T cells (T-reg). METHODS: Acute phase samples (9) and post-recovery samples (14) from cases of SJS or TEN to LTG were provided by the RegiSCAR-study group. Controls were persons never exposed to LTG (12), patients exposed without reaction (6), and patients who developed a mild eruption to LTG (6). LTT was performed by measuring (3) H-thymidine incorporation after 3 days of incubation with phytohemmaglutinin, LTG (10 µg/mL) or medium. Stimulation index ≥ 2 was considered positive. In 16 cases LTT was redone after depletion of T-reg by fluorescence activated cell sorting. RESULTS: Positive LTT was observed in 3/6 cases of mild eruptions, 1/9 SJS/TEN-cases tested during the acute phase and 3/14 SJS/TEN-cases tested after recovery. We noted a very mild and nonsignificant trend for an increased response after depletion of T-reg in late samples from SJS or TEN patients. CONCLUSIONS AND CLINICAL RELEVANCE: With the largest number of LTT performed in patients with SJS or TEN to a single drug, we confirmed that reactive cells are rarely detected in these reactions. Poor reactivity did not seem related to T-reg. Other in vitro assays than those testing proliferation should be evaluated, before raising the hypothesis that specific cells disappeared by undergoing apoptosis during the reaction.

[New developments in Sézary syndrome]. / Actualités sur le syndrome de Sézary.

Sézary syndrome (SS) represents 3% of cutaneous T-cell lymphomas (CTCL). It is an aggressive epidermotropic CTCL with a 5-year survival rate of 24%. According to EORTC (European organization for research and treatment of cancer), SS is defined by erythroderma, diffuse lymphadenopathy, atypical T lymphocytes (>1000/mm(3)), and the presence of a major blood, cutaneous and nodal T cell clone. A specific marker for atypical tumoral T lymphocytes known as Sézary cells was identified in 2001, namely KIR3DL2 (CD158k) receptor, which allows more specific diagnosis of SS; levels of this marker are highly correlated with the clinical course of the disease. In therapeutic terms, clinical trials are being conducted on new molecules that point towards an improved prognosis for this disease. We propose a review of Sézary syndrome, which is currently the subject of scientific papers concerning both physiopathology and therapeutics, with new prospects of targeted therapy.

Detection of T cell receptor alpha chain locus rearrangements in human antigen-specific T lymphocyte clones using a DNA probe specific for chromosome region 14q11.

Human cloned antigen-specific T lymphocytes were used to characterize DNA rearrangements using a cDNA probe from the T cell receptor (TCR)-alpha chain gene. Rearranged patterns were detected in some T cell clones, confirming that normal mature T cells are rearranged in TCR-alpha locus. Similarly, rearranged DNA patterns were found in T cell clones from the same panel, using a DNA probe (clone K-40, [1]) isolated from chromosome 14 (14q11), where the TCR-alpha locus has been mapped. These results suggest that this genomic DNA clone is located within the TCR-alpha chain locus.

Delineation of an immunoregulatory amplifier population recognizing autologous Ia molecules. Analysis with human T cell clones.

Autoreactive T lymphocytes were generated by culturing human peripheral blood mononuclear cells with an antigen-specific major histocompatibility complex (MHC)-restricted autologous inducer T cell, termed RW17C and subsequently cloned in soft agar. The majority of such clones (AC1-13) expressed the T3+T4+T8-T11+Ia+ phenotype and were directed at autologous class II MHC gene products found on B cells, macrophages, and B lymphoblastoid cells as judged by their proliferative response to the latter. For this recognition, the clones employed a T3-Ti molecular complex and a T4 structure analogous to those found on allospecific T cells. Perhaps more importantly, it was observed that the same AC1-13 autoreactive clones (AC) induced autologous B cells to produce high levels of immunoglobulin in the absence of exogenous antigen and could synergize with the RW17C clone to effect maximal B cell Ig production. These results support the notion that such autoreactive cells can function in a physiologic amplifier role by facilitating induction via an internal set of signals (i.e. autologous MHC).

Functional isotypes are not encoded by the constant region genes of the beta subunit of the T cell receptor for antigen/major histocompatibility complex.

Human T cell clones and a cDNA probe specific for constant regions of the beta subunit of the antigen/major histocompatibility complex (MHC) receptor, TiC beta 1 and TiC beta 2, were employed to determine whether these genes were differentially used by functional classes of T lymphocytes. DNA from 10 interleukin-2-dependent T cell clones including class I and class II MHC-specific cytotoxic T lymphocytes (n = 6), T4+ inducer T lymphocytes (n = 2), and T8+ suppressor T lymphocytes (n = 2) showed rearrangement of the TiC beta 1 gene on Southern blot analysis with or without deletion of the other TiC beta 1 allele. In contrast, TiC beta 2 always remained in germline configuration. Moreover, the finding that one additional suppressor clone deleted both TiC beta 1 alleles, maintained a germline TiC beta 2 configuration, and yet actively transcribed TiC beta 2 message suggested that TiC beta 2 is not a pseudogene. Rather, it appeared to be used less frequently than the TiC beta 1 gene and in the absence of detectable DNA rearrangements. Together, these results demonstrate that the functional repertoire (or isotype) of a given subclass of T cells is not encoded within the Ti beta genes.

A novel 80-kD cell surface structure identifies human circulating lymphocytes with natural killer activity.

Human lymphocytes with natural killer (NK) activity, including most activated gamma/delta+ T lymphocytes, recognize and lyse tumor target cells without requiring recognition of major histocompatibility complex antigen. However, unlike gamma/delta+ T lymphocytes, NK cells do not express CD3/T cell receptor (TCR) molecules, and the receptors involved in cell-mediated cytotoxicity are unknown. To further delineate circulating NK cells, we developed monoclonal antibodies (mAbs) against the human NK leukemia YT2C2. We report the isolation of a mAb termed BY55, recognizing at the cell surface a novel 80-kD protein with restricted expression. In addition to the immunizing cell line, this mAb binds to circulating NK cells, gamma/delta+ cells, and a minor subset of alpha/beta+ T lymphocytes. Expression of the BY55 mAb-reactive epitope/molecule is regulated by activation, as short-term culture of peripheral blood lymphocytes (PBL) with phorbol ester induced its downmodulation. Furthermore, BY55 mAb reactivity was found neither with the NK nor with the TCR alpha/beta+ gamma/delta+ clones tested. Biochemical studies as well as phenotypic analysis revealed that this structure is different from all previously identified molecules on the lymphocyte cell surface. Interestingly, we found that BY55+ cells exert most NK activity obtained with fresh circulating lymphocytes. We report that within fresh E rosette-positive PBL only a subset of the CD16+, CD56+, and CD57+ cells coexpressed BY55 molecule, indicating that BY55 mAb defines a unique subset mediating NK activity of circulating PBL.

Suppression of the human allogenetic response in vitro with primed lymphocytes and suppressive supernates.

Human lymphocytes primed in vitro by allogeneic cells develop lymphocyte populations with different functions. Cells with a memory of the allogeneic contact and cytotoxic effectors have been identified previously. We now report on a third lymphocyte population generated by repeated in vitro sensitization. This is of suppressor lymphocytes that can inhibit the primary proliferation of unsensitized lymphocytes. Our experiments indicate that these human suppressor cells are most probably T lymphocytes, adherent to glass or nylon wool, and radioresistant. They derive from both the large blast cells and the small, nondividing lymphocytes that are observed on day 7 of the allogeneic response. The suppressor cells release suppressor factor(s) upon restimulation. Studies on the specificity of the suppression have shown that suppressor cells are specific to the HLA-DR antigens presented by stimulator lymphocytes and that they probably release the suppressor factor only when confronted with the specific HLA-DR antigen. However, when the suppressor factor is produced, the proliferative response to any stimulating cell is inhibited regardless of its HLA-DR antigens. On the other hand, the suppressor factor can only suppress the proliferation of lymphocytes from some individuals. This restriction suggests that suppression can only occur when the producer of the suppressor factor and the responding lymphocytes that are being tested, have some identities in common. No evidence in favor of an HLA-D restriction has been obtained so far.

T cell receptor (TCR) interacting molecule (TRIM), a novel disulfide-linked dimer associated with the TCR-CD3-zeta complex, recruits intracellular signaling proteins to the plasma membrane.

The molecular mechanisms regulating recruitment of intracellular signaling proteins like growth factor receptor-bound protein 2 (Grb2), phospholipase Cgamma1, or phosphatidylinositol 3-kinase (PI3-kinase) to the plasma membrane after stimulation of the T cell receptor (TCR)- CD3-zeta complex are not very well understood. We describe here purification, tandem mass spectrometry sequencing, molecular cloning, and biochemical characterization of a novel transmembrane adaptor protein which associates and comodulates with the TCR-CD3-zeta complex in human T lymphocytes and T cell lines. This protein was termed T cell receptor interacting molecule (TRIM). TRIM is a disulfide-linked homodimer which is comprised of a short extracellular domain of 8 amino acids, a 19-amino acid transmembrane region, and a 159-amino acid cytoplasmic tail. In its intracellular domain, TRIM contains several tyrosine-based signaling motifs that could be involved in SH2 domain-mediated protein-protein interactions. Indeed, after T cell activation, TRIM becomes rapidly phosphorylated on tyrosine residues and then associates with the 85-kD regulatory subunit of PI3-kinase via an YxxM motif. Thus, TRIM represents a TCR-associated transmembrane adaptor protein which is likely involved in targeting of intracellular signaling proteins to the plasma membrane after triggering of the TCR.

Regulation of transcription of the human T cell antigen receptor delta chain gene. A T lineage-specific enhancer element is located in the J delta 3-C delta intron.

We have defined transcriptional enhancing sequences inside the TCR-delta gene locus, using transient transfections with constructs containing DNA fragments cloned upstream to a reporter gene fused to a heterologous promoter. A 14-kb DNA region extending from the J delta 3 segment to 6 kb 3' to C delta was analyzed. We show the presence of positive regulatory sequences inside the J delta 3-C delta intron and have localized these sequences to two DNA fragments of approximately 300 and 258 bp. Analysis of cell specificity of the activation of such sequences demonstrates a T cell pattern for one of the two fragments. The nucleotide sequence of the T cell-specific element shows motifs sharing homology with previously described core enhancers.

Absolute CD3+ CD158k+ lymphocyte count is reliable and more sensitive than cytomorphology to evaluate blood tumour burden in Sézary syndrome.

Background CD158k/KIR3DL2 is a specific marker for Sézary cells which can be used to diagnose Sézary syndrome (SS) in erythrodermic patients with abnormal circulating T cells. Objectives To evaluate the suitability of CD158k/KIR3DL2 for detecting and evaluating blood tumour load during the follow up of patients with SS. Methods The absolute CD3+ CD158k+ lymphocyte count was compared with the absolute count of cytomorphological Sézary cells and was correlated with clinical flares in a cohort of patients with SS. Twenty-five patients were included in the study and 48 blood samples were analysed. Results The absolute count of CD3+ CD158k+ cells strongly correlated with the absolute count of atypical circulating cells (r = 0.97, P < 10(-15)). The CD3+ CD158k+ lymphocyte cell count was in eight cases more sensitive than cytomorphology for detecting atypical circulating cells especially for small-sized tumour cells. The tumour burden evaluated by CD3+ CD158k+ immunostaining was significantly associated with clinical flare (P < 10(-4)). Conclusions CD3+ CD158k+ phenotyping is a reliable and objective test to monitor the blood tumour burden in patients with SS under systemic therapy.

Identification and analysis of the human CD160 promoter: implication of a potential AML-1 binding site in promoter activation.

CD160 is a glycosylphosphatidylinositol-anchored multimer expressed at the cell surface of subsets of cytotoxic T-lymphocytes and natural killer cells. Although CD160 is an important molecule for the control of cell-mediated cytotoxic responses, the mechanisms of regulation of its expression is unknown. We investigated the regulation of CD160 transcription by localizing and analyzing its promoter. The CD160 gene is encoded on chromosome 1, contains 6 exons with the translation initiation codon in exon 3. Bioinformatics analysis pointed to three potential promoter regions, two upstream of exon 1 and one in front of exon 3. RACE-PCR analysis identified a single transcription start site (TSS) and reporter gene transfections localized the active region immediately upstream of exon 1. Sequential deletion analysis led to the identification of a 371 bp sequence, located between -314 and +57 relative to the TSS, as the core promoter sequence driving CD160 gene transcription. Sequence alignment of the mouse and human CD160 genomic promoter region revealed a strong homology in the 371 bp sequence identified and pointed out to three conserved transcription factor binding sites for acute myelogenous leukemia-1 (AML-1), FREAC-4 and Sox17. Site-directed mutagenesis showed that the predicted AML-1 site is essential for the regulation of CD160 gene expression.