Targeting MICA/B with cytotoxic therapeutic antibodies leads to tumor control

Background: MICA and MICB are tightly regulated stress-induced proteins that trigger the immune system by binding to the activating receptor NKG2D on cytotoxic lymphocytes. MICA and MICB are highly polymorphic molecules with prevalent expression on several types of solid tumors and limited expression in normal/healthy tissues, making them attractive targets for therapeutic intervention. Methods: We have generated a series of anti-MICA and MICB cross-reactive antibodies with the unique feature of binding to the most prevalent isoforms of both these molecules. Results: The anti-MICA and MICB antibody MICAB1, a human IgG1 Fc-engineered monoclonal antibody (mAb), displayed potent antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) of MICA/B-expressing tumor cells in vitro. However, it showed insufficient efficiency against solid tumors in vivo, which prompted the development of antibody-drug conjugates (ADC). Indeed, optimal tumor control was achieved with MICAB1-ADC format in several solid tumor models, including patient-derived xenografts (PDX) and carcinogen-induced tumors in immunocompetent MICAgen transgenic mice. Conclusions: These data indicate that MICA and MICB are promising targets for cytotoxic immunotherapy.

Targeting MICA/B with cytotoxic therapeutic antibodies leads to tumor control

Background: MICA and MICB are tightly regulated stress-induced proteins that trigger the immune system by binding to the activating receptor NKG2D on cytotoxic lymphocytes. MICA and MICB are highly polymorphic molecules with prevalent expression on several types of solid tumors and limited expression in normal/healthy tissues, making them attractive targets for therapeutic intervention. Methods: We have generated a series of anti-MICA and MICB cross-reactive antibodies with the unique feature of binding to the most prevalent isoforms of both these molecules. Results: The anti-MICA and MICB antibody MICAB1, a human IgG1 Fc-engineered monoclonal antibody (mAb), displayed potent antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) of MICA/B-expressing tumor cells in vitro. However, it showed insufficient efficiency against solid tumors in vivo, which prompted the development of antibody-drug conjugates (ADC). Indeed, optimal tumor control was achieved with MICAB1-ADC format in several solid tumor models, including patient-derived xenografts (PDX) and carcinogen-induced tumors in immunocompetent MICAgen transgenic mice. Conclusions: These data indicate that MICA and MICB are promising targets for cytotoxic immunotherapy.

MICAgen Mice Recapitulate the Highly Restricted but Activation-Inducible Expression of the Paradigmatic Human NKG2D Ligand MICA

NKG2D is a potent activating immunoreceptor expressed on nearly all cytotoxic lymphocytes promoting their cytotoxicity against self-cells expressing NKG2D ligands (NKG2DLs). NKG2DLs are MHC class I-like glycoproteins that usually are not expressed on "healthy" cells. Rather, their surface expression is induced by various forms of cellular stress, viral infection, or malignant transformation. Hence, cell surface NKG2DLs mark "dangerous" cells for elimination by cytotoxic lymphocytes and therefore can be considered as "kill-me" signals. In addition, NKG2DLs are up-regulated on activated leukocytes, which facilitates containment of immune responses. While the NKG2D receptor is conserved among mammals, NKG2DL genes have rapidly diversified during mammalian speciation, likely due to strong selective pressures exerted by species-specific pathogens. Consequently, NKG2DL genes are not conserved in man and mice, although their NKG2D-binding domains maintained structural homology. Human NKG2DLs comprise two members of the MIC (MICA/MICB) and six members of the ULBP family of glycoproteins (ULBP1-6) with MICA representing the best-studied human NKG2DLs by far. Many of these studies implicate a role of MICA in various malignant, infectious, or autoimmune diseases. However, conclusions from these studies often were limited in default of supporting in vivo experiments. Here, we report a MICA transgenic (MICAgen) mouse model that replicates central features of human MICA expression and function and, therefore, constitutes a novel tool to critically assess and extend conclusions from previous in vitro studies on MICA. Similarly to humans, MICA transcripts are broadly present in organs of MICAgen mice, while MICA glycoproteins are barely detectable. Upon activation, hematopoietic cells up-regulate and proteolytically shed surface MICA. Shed soluble MICA (sMICA) is also present in plasma of MICAgen mice but affects neither surface NKG2D expression of circulating NK cells nor their functional recognition of MICA-expressing tumor cells. Accordingly, MICAgen mice also show a delayed growth of MICA-expressing B16F10 tumors, not accompanied by an emergence of MICA-specific antibodies. Such immunotolerance for the xenoantigen MICA ideally suits MICAgen mice for anti-MICA-based immunotherapies. Altogether, MICAgen mice represent a valuable model to study regulation, function, disease relevance, and therapeutic targeting of MICA in vivo.

Anti-NKG2A mAb Is a Checkpoint Inhibitor that Promotes Anti-tumor Immunity by Unleashing Both T and NK Cells

Checkpoint inhibitors have revolutionized cancer treatment. However, only a minority of patients respond to these immunotherapies. Here, we report that blocking the inhibitory NKG2A receptor enhances tumor immunity by promoting both natural killer (NK) and CD8⁺ T cell effector functions in mice and humans. Monalizumab, a humanized anti-NKG2A antibody, enhanced NK cell activity against various tumor cells and rescued CD8⁺ T cell function in combination with PD-x axis blockade. Monalizumab also stimulated NK cell activity against antibody-coated target cells. Interim results of a phase II trial of monalizumab plus cetuximab in previously treated squamous cell carcinoma of the head and neck showed a 31% objective response rate. Most common adverse events were fatigue (17%), pyrexia (13%), and headache (10%). NKG2A targeting with monalizumab is thus a novel checkpoint inhibitory mechanism promoting anti-tumor immunity by enhancing the activity of both T and NK cells, which may complement first-generation immunotherapies against cancer.

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Blocking NKG2A unleashes both T and NK cell effector functions

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Combined blocking of the NKG2A and the PD-1 axis promotes anti-tumor immunity

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Blocking NKG2A and triggering CD16 illustrates the efficacy of dual checkpoint therapy

Abstract 1690: NKG2A immune checkpoint blockade potentiates cetuximab induced ADCC in head and neck cancer preclinical model

Monalizumab (IPH2201) is a first-in-class humanized IgG4 targeting NKG2A (Natural Killer Group 2A), which is expressed as a heterodimer with CD94 at the surface of subsets of NK (Natural Killer) cells, γδ T cells and tumor infiltrating CD8+ T cells. This inhibitory receptor binds to HLA-E (Human Leukocytes Antigen-E) molecules that are frequently up-regulated on human cancer cells, preventing from killing by NKG2A+ immune cells. HLA-E is expressed on most of the patients with Head and Neck Squamous Cell Cancer (HNSCC). Monalizumab blocks the binding of CD94/NKG2A to HLA-E, reducing inhibitory signaling thereby unleashing NK and T cell responses. High expression of EGFR occurs in most epithelial malignancies and particularly in HNSCC and is associated with poor prognosis. The anti-EGFR monoclonal antibody cetuximab (Ctx) is thought to act through blocking oncogenic signaling and by inducing Fcγ receptor-mediated antibody dependent cell cytotoxicity (ADCC) which involves human NK cells. We investigated ex vivo and in vitro the rationale of combining monalizumab with Ctx in the treatment of oral cancers. We first analyzed formalin-fixed paraffin-embedded samples of HNSCC patients by immunohistochemistry (n=65). We confirmed that HLA-E was expressed on carcinoma cells in all patients. We also observed that most of the tumors were highly infiltrated by CD8+ T cells both in the tumor beds and in the stroma and that the majority of tumors were also infiltrated by NKp46+ NK cells in higher numbers in the non-metastatic tumors. Interestingly, HNSCC was found as being one of the tumor types with the highest NKp46+ cell density as compared with renal cell carcinoma, non-small cell lung cancer, colorectal cancer or pancreatic tumors. Moreover CD94+ lymphocytes were detected in the stroma and tumor beds in close contact to tumor cells in about half of the patients. Using multicolor flow cytometry, NK cells and CD8+ T cells from tumor and non-involved adjacent tissues, metastatic lymph nodes and peripheral blood from patients relapsing post-chemotherapy were characterized for expression of activating and inhibitory receptors. Interestingly, NKG2A expression was higher on tumor infiltrating NK cells (CD56dim or CD56bright) and CD8+ T cell compared to the one observed in non-involved adjacent tissue, metastatic lymph node or blood. In vitro, monalizumab increased CD107 mobilization and CD137 upregulation on NKG2A+ NK cells in response to HNSCC cell lines with endogenous HLA-E expression and enhanced Ctx-mediated ADCC in a dose dependent manner. Altogether, these data support the rationale for investigating monalizumab in HNSCC patients and in combination with cetuximab in clinical trials (NCT02643550).

Citation Format: Caroline Soulas, Ana Lalanne, Cécile Bonnafous, Caroline Hoffman, Elodie Bonnet, Arnaud Dujardin, Violette Breso, Mathieu Bléry, Olivier Lantz, Romain Remark, Eric Vivier, Pascale Andre. NKG2A immune checkpoint blockade potentiates cetuximab induced ADCC in head and neck cancer preclinical model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1690.

High mTOR activity is a hallmark of reactive natural killer cells and amplifies early signaling through activating receptors

NK cell education is the process through which chronic engagement of inhibitory NK cell receptors by self MHC-I molecules preserves cellular responsiveness. The molecular mechanisms responsible for NK cell education remain unclear. Here, we show that mouse NK cell education is associated with a higher basal activity of the mTOR/Akt pathway, commensurate to the number of educating receptors. This higher activity was dependent on the SHP-1 phosphatase and essential for the improved responsiveness of reactive NK cells. Upon stimulation, the mTOR/Akt pathway amplified signaling through activating NK cell receptors by enhancing calcium flux and LFA-1 integrin activation. Pharmacological inhibition of mTOR resulted in a proportional decrease in NK cell reactivity. Reciprocally, acute cytokine stimulation restored reactivity of hyporesponsive NK cells through mTOR activation. These results demonstrate that mTOR acts as a molecular rheostat of NK cell reactivity controlled by educating receptors and uncover how cytokine stimulation overcomes NK cell education.

The cells of the immune system patrol the body to detect and destroy harmful microbes and diseased cells. Natural killer cells are immune cells with a natural capacity to kill infected or cancerous cells, as their name suggests. Importantly, they do so while sparing the surrounding healthy cells.

As natural killer cells mature they go through an “education” process to learn to distinguish between normal and abnormal cells. During education, the natural killer cells interact continuously with nearby healthy cells. However, it remains unknown how these interactions change the natural killer cells, or how these changes control their killing activity.

Marçais et al. now show that a protein called mTOR is essential to the education of natural killer cells. Comparing natural killer cells that had or had not completed the education process revealed that mTOR is more active in the educated cells. Moreover, inhibiting the activity of mTOR caused educated natural killer cells to lose their ability to identify diseased cells, while stimulating mTOR activity in uneducated natural killer cells mimicked the education process, allowing them to recognize and eliminate diseased host cells.

Certain nutrients are known to control the activity of mTOR, which suggests these nutrients could also affect how natural killer cells develop. In addition, manipulating the activity of mTOR could be used to control the response of natural killer cells to diseased host cells, and so could form part of treatments for cancer and infectious diseases. However, given that mTOR plays numerous roles within different body cells, any potential therapies that are developed would need to be able to manipulate mTOR specifically in natural killer cells.

Effects of anti-NKG2A antibody administration on leukemia and normal hematopoietic cells

Natural killer cells are key cells of the innate immune system. Natural killer cell receptor repertoires are diversified by a stochastic expression of killer-cell-immunoglobulin-like receptors and lectin-like receptors such as NKG2 receptors. All individuals harbor a subset of natural killer cells expressing NKG2A, the inhibitory checkpoint receptor for HLA-E. Most neoplastic and normal hematopoietic cells express HLA-E, the inhibitory ligand of NKG2A. A novel anti-human NKG2A antibody induced tumor cell death, suggesting that the antibody could be useful in the treatment of cancers expressing HLA-E. We found that immunodeficient mice, co-infused with human primary leukemia or Epstein-Barr virus cell lines and NKG2A(+) natural killer cells, pre-treated with anti-human NKG2A, were rescued from disease progression. Human NKG2A(+) natural killer cells reconstituted in immunodeficient mice after transplantation of human CD34(+) cells. These natural killer cells are able to kill engrafted human primary leukemia or Epstein-Barr virus cell lines by lysis after intraperitoneal administration of anti-human NKG2A. Thus, this anti-NKG2A may exploit the anti-leukemic action of the wave of NKG2A(+) natural killer cells recovering after hematopoietic stem cell transplants or adoptive therapy with natural killer cell infusions from matched or mismatched family donors after chemotherapy for acute leukemia, without the need to search for a natural killer cell alloreactive donor.

IPH4102, a humanized KIR3DL2 antibody with potent activity against cutaneous T-cell lymphoma

Advanced cutaneous T-cell lymphoma (CTCL) remains an unmet medical need, which lacks effective targeted therapies. In this study, we report the development of IPH4102, a humanized monoclonal antibody that targets the immune receptor KIR3DL2, which is widely expressed on CTCL cells but few normal immune cells. Potent antitumor properties of IPH4102 were documented in allogeneic human CTCL cells and a mouse model of KIR3DL2(+) disease. IPH4102 antitumor activity was mediated by antibody-dependent cell cytotoxicity and phagocytosis. IPH4102 improved survival and reduced tumor growth in mice inoculated with KIR3DL2(+) tumors. Ex vivo efficacy was further evaluated in primary Sézary patient cells, sorted natural killer-based autologous assays, and direct spiking into Sézary patient peripheral blood mononuclear cells. In these settings, IPH4102 selectively and efficiently killed primary Sézary cells, including at unfavorable effector-to-target ratios characteristic of unsorted PBMC. Together, our results offer preclinical proof of concept for the clinical development of IPH4102 to treat patients with advanced CTCL.

Antibody engineering and therapeutics, The Annual Meeting of the Antibody Society: December 8-12, 2013, Huntington Beach, CA

The 24^th Antibody Engineering & Therapeutics meeting brought together a broad range of participants who were updated on the latest advances in antibody research and development. Organized by IBC Life Sciences, the gathering is the annual meeting of The Antibody Society, which serves as the scientific sponsor. Preconference workshops on 3D modeling and delineation of clonal lineages were featured, and the conference included sessions on a wide variety of topics relevant to researchers, including systems biology; antibody deep sequencing and repertoires; the effects of antibody gene variation and usage on antibody response; directed evolution; knowledge-based design; antibodies in a complex environment; polyreactive antibodies and polyspecificity; the interface between antibody therapy and cellular immunity in cancer; antibodies in cardiometabolic medicine; antibody pharmacokinetics, distribution and off-target toxicity; optimizing antibody formats for immunotherapy; polyclonals, oligoclonals and bispecifics; antibody discovery platforms; and antibody-drug conjugates.

NK cells in central nervous system disorders

NK cells are important players in immunity against pathogens and neoplasms. As a component of the innate immune system, they are one of the first effectors on sites of inflammation. Through their cytokine production capacities, NK cells participate in the development of a potent adaptive immune response. Furthermore, NK cells were found to have regulatory functions to limit and prevent autoimmunity via killing of autologous immune cells. These paradoxical functions of NK cells are reflected in CNS disorders. In this review, we discuss the phenotypes and functional features of peripheral and brain NK cells in brain tumors and infections, neurodegenerative diseases, acute vascular and traumatic damage, as well as mental disorders. We also discuss the implication of NK cells in neurotoxicity and neuroprotection following CNS pathology, as well as the crosstalk between NK cells and brain-resident immune cells.

Identification, activation, and selective in vivo ablation of mouse NK cells via NKp46

Natural killer (NK) cells contribute to a variety of innate immune responses to viruses, tumors and allogeneic cells. However, our understanding of NK cell biology is severely limited by the lack of consensus phenotypic definition of these cells across species, by the lack of specific marker to visualize them in situ, and by the lack of a genetic model where NK cells may be selectively ablated. NKp46/CD335 is an Ig-like superfamily cell surface receptor involved in human NK cell activation. In addition to human, we show here that NKp46 is expressed by NK cells in all mouse strains analyzed, as well as in three common monkey species, prompting a unifying phenotypic definition of NK cells across species based on NKp46 cell surface expression. Mouse NKp46 triggers NK cell effector function and allows the detection of NK cells in situ. NKp46 expression parallels cell engagement into NK differentiation programs because it is detected on all NK cells from the immature CD122(+)NK1.1(+)DX5(-) stage and on a minute fraction of NK-like T cells, but not on CD1d-restricted NKT cells. Moreover, human NKp46 promoter drives NK cell selective expression both in vitro and in vivo. Using NKp46 promoter, we generated transgenic mice expressing EGFP and the diphtheria toxin (DT) receptor in NK cells. DT injection in these mice leads to a complete and selective NK cell ablation. This model paves a way for the in vivo characterization and preclinical assessment of NK cell biological function.

Essential role of membrane cholesterol in accelerated BCR internalization and uncoupling from NF-kappa B in B cell clonal anergy

Divergent hypotheses exist to explain how signaling by the B cell receptor (BCR) is initiated after antigen binding and how it is qualitatively altered in anergic B cells to selectively uncouple from nuclear factor kappaB and c-Jun N-terminal kinase pathways while continuing to activate extracellular signal-regulated kinase and calcium-nuclear factor of activated T cell pathways. Here we find that BCRs on anergic cells are endocytosed at a very enhanced rate upon binding antigen, resulting in a large steady-state pool of intracellularly sequestered receptors that appear to be continuously cycling between surface and intracellular compartments. This endocytic mechanism is exquisitely sensitive to the lowering of plasma membrane cholesterol by methyl-beta-cyclodextrin, and, when blocked in this way, the sequestered BCRs return to the cell surface and RelA nuclear accumulation is stimulated. In contrast, when plasma membrane cholesterol is lowered and GM1 sphingolipid markers of membrane rafts are depleted in naive B cells, this does not diminish BCR signaling to calcium or RelA. These results provide a possible explanation for the signaling changes in clonal anergy and indicate that a chief function of membrane cholesterol in B cells is not to initiate BCR signaling, but instead to terminate a subset of signals by rapid receptor internalization.

Inhibition of IgE-mediated mast cell activation by the paired Ig-like receptor PIR-B

The potential of the paired Ig-like receptors of activating (PIR-A) and inhibitory (PIR-B) types for modifying an IgE antibody-mediated allergic response was evaluated in mouse bone marrow-derived mast cells. Although mast cells produced both PIR-A and PIR-B, PIR-B was found to be preferentially expressed on the cell surface, where it was constitutively tyrosine phosphorylated and associated with intracellular SHP-1 protein tyrosine phosphatase. PIR-B coligation with the IgE receptor (FcepsilonRI) inhibited IgE-mediated mast cell activation and release of serotonin. Surprisingly, the inhibitory activity of PIR-B was unimpaired in SHP-1-deficient mast cells. A third functional tyrosine-based inhibitory motif, one that fails to bind the SHP-1, SHP-2, and SHIP phosphatases, was identified in parallel studies of FcepsilonRI-bearing rat basophilic leukemia (RBL) cells transfected with constructs having mutations in the PIR-B cytoplasmic region. These results define the preferential expression of the PIR-B molecules on mast cells and an inhibitory potential that can be mediated via a SHP-1-independent pathway.

[Evaluation of plain abdominal radiography prescriptions in a university hospital center]

OBJECTIVES

The aim of this study was to evaluate the prescription, impact and diagnostic utility of plain abdominal radiography in a University Hospital.

METHODS

Plain abdominal radiography series performed over 15 consecutive days were evaluated for quality and agreement with the patient's clinical status. Agreement between the final diagnosis and the radiographic findings were also compared. Contribution of plain abdominal radiography to final diagnosis was assessed on the basis of the conclusions on the hospital discharge report or from those drawn from a telephone survey. The same relationship was also assessed in terms of clinician status (medical student, resident physician, senior physician).

RESULTS

The series included 175 radiography series (11.6 per day). In 86% of the cases, the choice of views was adapted to the clinical context. In 14% it was not. The quality of the x-rays was found to be unsatisfactory in 17%, good in 63% and excellent in 20%. The radiography was considered to be contributive to the final diagnosis in 13% of the cases and non-contributive in 87%. Clinician status was not correlated with the degree of usefulness for final diagnosis. Finally, the prescription was in agreement with standard guidelines in 28% of the cases and not in agreement in 72%.

CONCLUSION

Plain abdominal radiographs are neither sensitive nor specific, frequently misleading, and costly per specific and correct diagnosis. Better physician awareness is required to limit the number of unnecessary examinations.

MR evaluation of factors predicting the development of rotator cuff tears

PURPOSE

The purpose of this work was to assess the incidence of various factors predicting impingement in the shoulder.

METHOD

MR examination was used to assess various anatomic parameters in 46 patients with clinical abnormalities of the shoulder and 40 asymptomatic volunteers. All patients had undergone surgery, showing no rotator cuff tear.

RESULTS

A few of the parameters evaluated were significantly different in the two groups: The acromion was more frequently curved or hook-shaped in patients than in volunteers. The acromiohumeral distances differed (4.87 mm in patients and 6.05 mm in volunteers); so did the coracohumeral distances (7.9 mm in patients and 8.9 mm in volunteers). The shape of the acromioclavicular joint and the anterior covering of the humerus, defined on the coronal view, also differed (1.07 mm in patients and 1.49 mm in volunteers). Only the shapes of the acromioclavicular joint and of the acromion were linked with age.

CONCLUSION

All these factors reflected a decrease in the acromiohumeral space, except for the anterior covering of the acromial arch, which could be due to anterior instability.

Primary malignant lymphoma of the urinary bladder: report of three cases and review of the literature

We report three cases of a primary malignant lymphoma of the urinary bladder. The radiological features revealed a sessile mass of the lateral wall for one case, a circumferential thickening in the second, and two separated masses of the bladder wall in the last case. Primary malignant lymphoma of the urinary bladder is extremely rare. From a review of the literature, the clinical and radiological findings are discussed. In this paper we report the first case of urinary bladder lymphoma presented on CTas multiple masses.

[Imaging of acute urinary infections in adults. Radiologic findings and strategy for imaging procedures]

Urinary infection is very common in women. Generally no imaging is needed. The role of imaging is mandatory in the following cases: renal infection, urinary obstructive syndrome, immuno-compromised patients. The results of imaging in pathology are described: pyelonephritis, renal and perinephric abscesses with or without phlegmon, perinephritis and emphysematous perinephritis. A strategy for imaging procedures is proposed.

[Evaluation of radiological medical practice at a hospital during night duty]

PURPOSE

To evaluate the radiological activity during night duty, in a University Hospital. Materials and methods. During 100 days, the radiological activity has been evaluated from examinations requiring radiologist (including US and CT, special X-ray examinations). The urgent nature and the agreement between the suspected disease and the final diagnose have been compared with the level of the clinician (medical student, resident, senior).

RESULTS

981 radiological examinations were performed on an emergency basis. In 39%, the examination was urgent or very urgent and for 61%, little urgent or non-urgent. The level of the clinician was correlated with the degree of emergency evaluated by the radiologist and with the agreement between suspected disease and the final diagnose (p<0. 0001).

CONCLUSION

During night duty, the medical activity in radiology is not justified only by emergency, but also by the continuous hospital activities. Better formation of the physician is required to limit the number of examinations.

Signaling pathways engaged by NK cell receptors: double concerto for activating receptors, inhibitory receptors and NK cells

Despite the absence of antigen-specific receptors at their surface, NK cells can selectively eliminate virus-infected cells, tumor cells and allogenic cells. A dynamic and precisely coordinated balance between activating and inhibitory receptors governs NK cell activation programs. Multiple activating and inhibitory NK cell surface molecules have been described, a group of them acting as receptors for MHC class I molecules. In spite of their heterogeneity, activating NK cell receptors present remarkable structural and functional homologies with T cell- and B cell-antigen receptors. Inhibitory NK cell receptors operate at early stages of activating cascades by recruiting protein tyrosine phosphatases via intra- cytoplasmic motifs (ITIM), a strategy which is widely conserved in hematopoietic and non-hematopoietic cells.

Early signaling via inhibitory and activating NK receptors

This review focuses on recent findings on the structural features of inhibitory NK cell receptors containing immunoreceptor tyrosine-based inhibition motif (ITIM) and of NK cell activating receptors, both in human and mouse. First, the study of the inhibitory killer cell immunoglobulin-like receptors (KIR) unveiled the presence of intracytoplasmic ITIM and their capacity to recruit protein tyrosine phosphatases such as SHP-1 in vivo. A brief summary of the known SHP-1 targets may help us to understand the inhibition mediated by the KIR. The characterization of ITIM thus allowed the definition of a large group of inhibitory cell surface receptors. The second part of the review describes the known NK cell activating receptors. Most of them require association with ITAM-containing polypeptides in order to mediate cell activation.

Intraluminal duodenal diverticulum: radiological and endoscopic ultrasonography findings of an unusual cause of acute pancreatitis

Intraluminal duodenal diverticulum is a rare congenital web of membrane which may be symptomatic when it becomes distended. This report describes a case revealed by presenting as an acute pancreatitis. The radiological findings are reported. The findings at CT, upper gastro-intestinal series, endoscopic ultrasound and endoscopic retrograde cholangiopancreatography are described and differential diagnostic features from choledochocele and duodenal duplication are discussed. By endoscopic ultrasonography, observation of a thin wall, without different layers such as choledochocele or duodenal duplication, may be useful for diagnosis.

[Emphysematous pyelonephritis: apropos of 4 cases]

PURPOSE

The propose of this study was to describe the imaging findings in four patients with emphysematous pyelonephritis and to perform a review of the literature.

MATERIAL AND METHODS

Four cases of emphysematous pyelonephritis are presented. US and CT examinations were available for all patients.

RESULTS

Gas within the kidney may be diagnosed by plain film or rarely by ultrasound, but its location and its extent are best evaluated by CT. A review of the literature shows that emphysematous pyelonephritis is a rare and life-threatening infection typically occurring in diabetic patients.

CONCLUSION

CT is useful for diagnosing emphysematous pyelonephritis, especially when symptoms fail to resolve promptly with medical therapy.

Gene structure, expression pattern, and biological activity of mouse killer cell activating receptor-associated protein (KARAP)/DAP-12

Natural killer cell and T cell subsets express at their cell surface a repertoire of receptors for MHC class I molecules, the natural killer cell receptors (NKRs). NKRs are characterized by the existence of inhibitory and activating isoforms, which are encoded by highly homologous but separate genes present in the same locus. Inhibitory isoforms express an intracytoplasmic immunoreceptor tyrosine-based inhibition motif, whereas activating isoforms lack any immunoreceptor tyrosine-based inhibition motif but harbor a charged amino acid residue in their transmembrane domain. We previously characterized KARAP (killer cell activating receptor-associated protein), a novel disulfide-linked tyrosine-phosphorylated dimer that selectively associates with the activating NKR isoforms. We report here the identification of the mouse KARAP gene, its localization on chromosome 7 and its genomic organization in five exons. Point mutation and transfection studies revealed that KARAP is a novel signaling transmembrane subunit whose transduction function depends on the integrity of an intracytoplasmic immunoreceptor tyrosine-based activation motif. In contrast to previous members of the immunoreceptor tyrosine-based activation motif polypeptide family, KARAP is ubiquitously expressed on hematopoietic and nonhematopoietic cells, suggesting its association with a broad range of activating receptors in a variety of tissues.

The paired Ig-like receptor PIR-B is an inhibitory receptor that recruits the protein-tyrosine phosphatase SHP-1

An emerging family of cell surface inhibitory receptors is characterized by the presence of intracytoplasmic immunoreceptor tyrosine-based inhibition motifs (ITIM). These ITIM-bearing inhibitory receptors, which are typically paired with activating isoforms, associate with Src homology domain 2-containing phosphatases following ITIM tyrosine phosphorylation. Two categories of phosphatases are recruited by the ITIM-bearing receptors: the protein-tyrosine phosphatases, SHP-1 and SHP-2, and the polyphosphate inositol 5-phosphatase, SHIP. The dynamic equilibrium of B cell activation is partially controlled by two well known ITIM-bearing receptors, CD22 and FcgammaRIIB, a low affinity receptor for IgG. We describe here that a murine ITIM-bearing molecule, PIR-B, can also negatively regulate B cell activation. Tyrosine-phosphorylated ITIMs allow PIR-B to associate with SHP-1 but not with SHIP. Engagement of PIR-B thereby initiates a SHP-1-dependent inhibitory pathway that may play an important role in regulating B lymphocyte activation.

[Imaging of prostatic leiomyosarcoma and contribution of MRI]

A case of leiomyosarcoma of the prostate is presented. Adult prostatic leiomyosarcoma is a rare tumor with a poor prognosis. US-CT and MRI findings are described.

Reconstituted killer cell inhibitory receptors for major histocompatibility complex class I molecules control mast cell activation induced via immunoreceptor tyrosine-based activation motifs

Natural killer and T cells express at their surface, members of a multigenic family of killer cell inhibitory receptors (KIR) for major histocompatibility complex Class I molecules. KIR engagement leads to the inhibition of natural killer and T cell activation programs. We investigated here the functional reconstitution of KIR in a non-lymphoid cell type. Using stable transfection in the RBL-2H3 mast cell line, we demonstrated that (i) KIR can inhibit signals induced by FcepsilonRIgamma or CD3zeta polypeptides that bear immunoreceptor tyrosine-based activation motifs; (ii) two distinct immunoreceptor tyrosine-based inhibition motifs-bearing receptors, i.e. KIR and FcgammaRIIB, use distinct inhibitory pathways since KIR engagement inhibits the intracellular Ca2+ release from endoplasmic reticulum stores, in contrast to FcgammaRIIB, which only inhibits extracellular Ca2+ entry; (iii) KIR require co-ligation with an immunoreceptor tyrosine-based activation motif-dependent receptor to mediate their inhibitory function. This latter finding is central to the mechanism by which KIR selectively inhibit only the activatory receptors in close vicinity. Taken together our observations also contribute to define and extend the family of immunoreceptor tyrosine-based inhibition motif-bearing receptors involved in the negative control of cell activation.

Transduction of cytotoxic signals in natural killer cells: a general model of fine tuning between activatory and inhibitory pathways in lymphocytes

NK-cells are large granular lymphocytes, which are capable of exerting two major types of effector function, cell cytotoxicity and lymphokine secretion. NK-cells can exert cell cytotoxicity in one of two ways. First, NK-cells are able to recognize and to induce the lysis of antibody-coated target cells during antibody-dependent cell cytotoxicity (ADCC). Second, during natural cytotoxicity NK-cells are also able to recognize and to induce the lysis of a variety of target cells, including primarily virus-infected cells as well as tumor cells. Recently, a novel mechanism has been elucidated which controls NK-cell-activation programs and which is based on the cell surface expression of killer-cell inhibitory receptors (KIR). We will review here the molecular dissection of this inhibitory signalling pathway which utilizes immunoreceptor tyrosine-based inhibition motifs (ITIM) expressed in KIR intracytoplasmic domain. We will also show that this strategy used by NK-cells to regulate their effector functions is a general decision mechanism which exists not only in T- and B-lymphocytes, but also in a variety of other hematopoietic cells.

Mammographic pattern due to residual Lipiodol after galactography

The purpose of this pictorial essay is to describe the different mammographic aspects of residual Lipiodol ultra fluid (LUF) after galactography, and to define some specific patterns, because it may in some cases mimic microcalcifications and give diagnostic problems. The mammograms of 14 patients, aged 32-63 years, presenting LUF residues related to previous galactography, were analyzed retrospectively. In 12 cases the diagnosis was easy because the patients presented a typical pattern on mammography and came with their initial galactography. In 2 cases the diagnosis was more difficult because the patients did not remember the previous injection and the progressive resorption mimicked perfectly intraductal calcification. Benign duct ectasia with inflammatory reaction to foreign bodies were found in 3 cases in which surgery was performed. Lipiodol ultra fluid is no longer used for galactography, but it may persist in breast ducts or cysts for years and seems to still be used in some countries. There are in most cases specific signs enabling the diagnosis.

Function of killer cell inhibitory receptors for MHC class I molecules

NK- and T-cells express at their surface, members of a multigenic family of killer-cell inhibitory receptors (KIR) for MHC Class I molecules. KIR engagement leads to the inhibition of NK- and T-cell activation programs. These receptors recruit the protein tyrosine phosphatases (PTPase), SHP-1 and SHP-2, upon tyrosine phosphorylation of immunoreceptor tyrosine-based inhibition motif (ITIM) expressed in both human and mouse KIR. We further define the ITIM amino acids sequence required in that recognition and demonstrate the critical role of the phosphoY-2 amino acid residue in this V/IxYxxL/V motif. In addition, using RBL-2H3 cells expressing endogenous Fc epsilonRI receptors as well as transfected CD25/CD3zeta chimera and p58.183 human KIR, we show that KIR inhibitory function requires co-engagement of KIR and ITAM-containing receptors. These results document the pathway used by KIR to down-regulate NK- and T-cell activation programs.

Polyhedral microcalcifications on mammograms: prevalence and morphometric analysis

OBJECTIVE

The purpose of this study was to determine the incidence and the mammographic appearance of polyhedral microcalcifications.

MATERIALS AND METHODS

Prospectively, we evaluated screening mammograms in 2000 women for polyhedral microcalcifications. The number of polyhedral microcalcifications on routine and magnification views was established, and a quantitative analysis was done to determine if the shape of the polyhedral microcalcifications varied in the different projections. The ratio between the longer axis (R) and the shorter axis (r) was calculated.

RESULTS

Two radiologists detected at least two polyhedral microcalcifications on one projection in 58 (3%) women. The number of polyhedral microcalcifications detected ranged from 2 to 47 (mean, 8.2) for screening mammograms and from 2 to 62 (mean, 13.4) on magnification views. Polyhedral microcalcifications were bilateral in 22 cases, scattered in one breast in 19 cases, segmental in 10 cases, and grouped in a cluster in seven cases. Lateral projections showed more rhombohedral microcalcifications, and craniocaudal projections showed more square microcalcifications.

CONCLUSION

The frequency of polyhedral microcalcifications is 3%. The shape of polyhedral microcalcifications varies: craniocaudal views show them to be square and lateral views show them to be rhombohedral.

Human and mouse killer-cell inhibitory receptors recruit PTP1C and PTP1D protein tyrosine phosphatases

NK cells express cell surface receptors for MHC class I proteins (KIR). Engagement of these receptors inhibits NK cell cytotoxic programs. KIR can be expressed on T cells, and their engagement also results in inhibition of effector functions initiated by the CD3/TCR complex. While human KIR genes belong to the Ig gene superfamily, mouse KIR belong to a family of dimeric lectins. Despite these distinct evolutionary origins, we show here that both HLA-Cw3-specific human p58.183 receptors and H-2D d/k-specific mouse Ly49A receptors recruit the same protein tyrosine phosphatases, PTP1C and PTP1D, upon phosphorylation of critical intracytoplasmic tyrosine residues. These results document a common pathway by which diverse KIR can down-regulate NK and T cell activation programs, and further define the sequence of the immunoreceptor tyrosine-based inhibitory motif (ITIM), initially described in FcgammaRIIB1, and expressed in both human and mouse KIR.

Human and mouse killer-cell inhibitory receptors recruit PTP1C and PTP1D protein tyrosine phosphatases

NK cells express cell surface receptors for MHC class I proteins (KIR). Engagement of these receptors inhibits NK cell cytotoxic programs. KIR can be expressed on T cells, and their engagement also results in inhibition of effector functions initiated by the CD3/TCR complex. While human KIR genes belong to the Ig gene superfamily, mouse KIR belong to a family of dimeric lectins. Despite these distinct evolutionary origins, we show here that both HLA-Cw3-specific human p58.183 receptors and H-2D d/k-specific mouse Ly49A receptors recruit the same protein tyrosine phosphatases, PTP1C and PTP1D, upon phosphorylation of critical intracytoplasmic tyrosine residues. These results document a common pathway by which diverse KIR can down-regulate NK and T cell activation programs, and further define the sequence of the immunoreceptor tyrosine-based inhibitory motif (ITIM), initially described in FcgammaRIIB1, and expressed in both human and mouse KIR.

Cholangiographic features in fibrosis and cirrhosis of the liver. Radiological-pathological correlation

The cholangiographic features of intrahepatic bile ducts associated with cirrhosis or fibrosis are not well known. In order to achieve a radiological-pathological correlation, we studied nine livers with fibrosis or cirrhosis excised at autopsy. Cholangiograms were obtained within 24 hr after death from the nonfixed liver and multiple tissues samples were taken for histologic examination. Radiological data were interpreted by two independent investigators blinded to the clinical and histological findings. Cirrhosis (alcoholic in 4, posthepatitis in two) was observed in six livers, fibrosis (alcoholic in 2, posthepatitis in one) in three. No liver with fibrosis had cholangiographic abnormalities. In contrast, cholangiography of all livers with cirrhosis was abnormal. Abnormalities were a diminished arborization, a decrease of the distal opacification, an irregularity of caliber, and a tortuous course of the bile ducts. Histological study showed that the irregular and tortuous course were due to compression of the bile ducts by regenerative nodules. Furthermore, a thick fibrosis was organized around the bile ducts. In conclusion, fibrosis alone was not associated with cholangiographic abnormalities. In cirrhotic livers, intrahepatic bile ducts showed an irregular and tortuous course, a diminished arborization and a decrease of the distal opacification. These abnormalities were secondary to the presence of regenerative nodules and fibrosis organized around the bile ducts.

Mammographic lesions suggestive of radial scars: microscopic findings in 40 cases

PURPOSE

To analyze the histologic appearance of mammographically detected lesions suspected of being radial scars.

MATERIALS AND METHODS

Mammographic and pathologic findings in 40 patients with a preoperative diagnosis of radial scar were reviewed retrospectively.

RESULTS

Pathologic examination revealed 20 pure radial scars, 12 pure carcinomas, and eight malignant lesions (seven tubular carcinomas and one infiltrating ductal carcinoma) associated with a radial scar. At mammography, no difference was noted between benign and malignant lesions according to size and shape of the spicule, size of the central core, and the presence of calcifications.

CONCLUSION

Because of the association of radial scars with borderline and malignant lesions, a spiculated lesion suggestive of a radial scar found at mammography must always be surgically removed. The surgeon and pathologist must be aware of the mammographic aspects of radial scar, however, to avert excessive surgery, because all cancers in this study had a good prognosis.

[Tuberculous tenosynovitis of the wrist: ultrasonographic diagnosis and contribution of MRI]

Chronic tenosynovitis of the hand due to Mycobacterium tuberculosis has become rare. In the two cases presented here, the final diagnosis was obtained by isolation of the organism in the intercarpal fluid (1 case), or by a synovial biopsy (1 case). Ultrasonography showed a hypoechoic thickening of one or several tendon sheaths. MR enabled better differentiation between the thickening of the synovium itself and a fluid effusion. The criteria permitting to differentiate tuberculous from non-infectious tenosynovitis are: young age, male sex, specific epidemiological factors, elevated erythrocyte sedimentation rate, marked local swelling, association with other foci of tuberculosis, unusual exudation and synovial thickening, and association with osteitis.