Identity of Leu-19 (CD56) leukocyte differentiation antigen and neural cell adhesion molecule

Polysialic acid: biosynthesis, novel functions and applications

As an anti-adhesive, a reservoir for key biological molecules, and a modulator of signaling, polysialic acid (polySia) is critical for nervous system development and maintenance, promotes cancer metastasis, tissue regeneration and repair, and is implicated in psychiatric diseases. In this review, we focus on the biosynthesis and functions of mammalian polySia, and the use of polySia in therapeutic applications. PolySia modifies a small subset of mammalian glycoproteins, with the neural cell adhesion molecule, NCAM, serving as its major carrier. Studies show that mammalian polysialyltransferases employ a unique recognition mechanism to limit the addition of polySia to a select group of proteins. PolySia has long been considered an anti-adhesive molecule, and its impact on cell adhesion and signaling attributed directly to this property. However, recent studies have shown that polySia specifically binds neurotrophins, growth factors, and neurotransmitters and that this binding depends on chain length. This work highlights the importance of considering polySia quality and quantity, and not simply its presence or absence, as its various roles are explored. The capsular polySia of neuroinvasive bacteria allows these organisms to evade the host immune response. While this "stealth" characteristic has made meningitis vaccine development difficult, it has also made polySia a worthy replacement for polyetheylene glycol in the generation of therapeutic proteins with low immunogenicity and improved circulating half-lives. Bacterial polysialyltransferases are more promiscuous than the protein-specific mammalian enzymes, and new studies suggest that these enzymes have tremendous therapeutic potential, especially for strategies aimed at neural regeneration and tissue repair.

Expression of papillary thyroid carcinoma-associated molecular markers and their significance in follicular epithelial dysplasia with papillary thyroid carcinoma-like nuclear alterations in Hashimoto's thyroiditis

The aim of this study was to evaluate the expression of papillary thyroid carcinoma (PTC)-associated tumor markers in follicular epithelial dysplasia showing PTC-like nuclear alterations (FED) in Hashimoto's thyroiditis (HT) and to explore the relationship between HT and PTC. In this study, 43 PTC, 18 HT with FED and 16 peritumoral benign thyroid tissues were immunohistochemically analyzed for CK19, galectin-3, HBME-1, CD56, claudin-1 and NGAL expression. Our research revealed that in HT, the expression of CK19, galectin-3, HBME-1, claudin-1 and NGAL was focal and limited to FED, while CD56 was strongly positive in FED and most Hürthle cells. The stain intensity of CK19, claudin-1 and NGAL in FED decreased compared with PTC, but were significantly higher than that in peritumoral benign thyroid tissues (all P < 0.0125). For galectin-3, HBME-1 and CD56, no statistically significant difference was detected between HT and peritumoral benign thyroid tissues (all P > 0.05). In conclusion, In HT, FED might be a precancerous condition closely associated with PTC development as they have overlaps in cytological and immunomarker profiles, indicating that in patients with HT, under prolonged stimuli from chronic inflammation, part of follicular epithelia may show regeneration, hyperplasia, Hürthle cell metaplasia and dysplasia, eventually malignant transformation. Hence, long term follow-up and regular inspection would be necessary for Hashimoto's thyroiditis with FED.

Direct involvement of CD56 in cytokine-induced killer-mediated lysis of CD56+ hematopoietic target cells

Cytokine-induced killer (CIK) cells are in-vitro-expanded T lymphocytes that represent a heterogeneous population. A large majority of CIK cells are CD3(+)CD56(+), and this population has been shown to confer a cytotoxic effect against tumor targets. The scope of this work was to study whether CD56 has a direct role in CIK-mediated cytotoxicity. Blocking of CD56 with the anti-CD56 monoclonal antibody GPR165 significantly reduced CIK-mediated lysis of three CD56(+) hematopoietic tumor cell lines (AML-NS8, NB4, and KCL22), whereas no effect was observed on three CD56(-) hematopoietic tumor cell lines (K562, REH, and MOLT-4). Knockdown of CD56 in CIK cells by short interfering RNA made the cells less cytotoxic against a CD56(+) target, and knockdown of CD56 in target cells with lentiviral short hairpin RNA significantly altered their susceptibility to CIK-mediated lysis. Our data suggest that homophilic interaction between CD56 molecules may occur in tumor-cell recognition, leading to CIK-mediated cell death.

Increased numbers and functional activity of CD56⁺ T cells in healthy cytomegalovirus positive subjects

Human T cells expressing CD56 are capable of tumour cell lysis following activation with interleukin-2 but their role in viral immunity has been less well studied. Proportions of CD56(+) T cells were found to be highly significantly increased in cytomegalovirus-seropositive (CMV(+) ) compared with seronegative (CMV(-) ) healthy subjects (9.1 ± 1.5% versus 3.7 ± 1.0%; P < 0.0001). Proportions of CD56(+) T cells expressing CD28, CD62L, CD127, CD161 and CCR7 were significantly lower in CMV(+) than CMV(-) subjects but those expressing CD4, CD8, CD45RO, CD57, CD58, CD94 and NKG2C were significantly increased (P < 0.05), some having the phenotype of T effector memory cells. Levels of pro-inflammatory cytokines and CD107a were significantly higher in CD56(+) T cells from CMV(+) than CMV(-) subjects following stimulation with CMV antigens. This also resulted in higher levels of proliferation in CD56(+) T cells from CMV(+) than CMV(-) subjects. Using Class I HLA pentamers, it was found that CD56(+) T cells from CMV(+) subjects contained similar proportions of antigen-specific CD8(+) T cells to CD56(-) T cells in donors of several different HLA types. These differences may reflect the expansion and enhanced functional activity of CMV-specific CD56(+) memory T cells. In view of the link between CD56 expression and T-cell cytotoxic function, this strongly implicates CD56(+) T cells as being an important component of the cytotoxic T-cell response to CMV in healthy carriers.

Role of cytolytic impairment of natural killer and natural killer T-cell populations in rheumatoid arthritis

Innate immunity has been widely accepted as one of the major cause for the alteration of immune system and progression of autoimmune diseases. Natural killer (NK) cells and natural killer T (NKT) cells have not been explored in clinical studies for their cytolytic components in association with rheumatoid arthritis (RA). The literature available for these potential candidates is controversial in terms of their protective or pathogenic role in disease severity of RA. Present study explained the role of NK and NKT cell populations and intracellular expression of caspases, perforin, granzymes A and B in the pathogenesis of RA in patients. DAS28 score was measured as the disease severity. Immunochemical parameters were studied by using monoclonal antibodies (mAbs) against different cell types in flow cytometry. Results indicated that that whatsoever is the change in percentage cell populations, ratio of NK and NKT cell populations always remained poised even in the disease state. Reactive oxygen species (ROS) levels were elevated with increased intracellular active caspase-3, perforin and granzyme expression in RA patients. Their elevated expressions were positively correlated with DAS28 suggesting the pathogenic role in RA. The expressions of pro-inflammatory cytokines were enhanced while the anti-inflammatory cytokine expressions were diminished in the patients. Present study may point towards futuristic therapeutic targets which can fascinate the pharmaceutical industries to selectively target these molecules in designing the therapeutic strategy of RA patients.

Analysis of serum miRNA profiles of myasthenia gravis patients

Myasthenia gravis (MG) is an autoimmune disease characterized by the presence of autoantibodies, mainly against the acetylcholine receptor (AChR). The mechanisms triggering and maintaining this chronic disease are unknown. MiRNAs are regulatory molecules that play a key role in the immune system and are altered in many autoimmune diseases. The aim of this study was to evaluate miRNA profiles in serum of 61 AChR MG patients. We studied serum from patients with early onset MG (n = 22), late onset MG (n = 27) and thymoma (n = 12), to identify alterations in the specific subgroups. In a discovery cohort, we analysed 381 miRNA arrays from 5 patients from each subgroup, and 5 healthy controls. The 15 patients had not received any treatment. We found 32 miRNAs in different levels in MG and analysed 8 of these in a validation cohort that included 46 of the MG patients. MiR15b, miR122, miR-140-3p, miR185, miR192, miR20b and miR-885-5p were in lower levels in MG patients than in controls. Our study suggests that different clinical phenotypes in MG share common altered mechanisms in circulating miRNAs, with no additional contribution of the thymoma. MG treatment intervention does not modify the profile of these miRNAs. Novel insights into the pathogenesis of MG can be reached by the analysis of circulating miRNAs since some of these miRNAs have also been found low in MG peripheral mononuclear cells, and have targets with important roles in B cell survival and antibody production.

Natural killer cells and killer-cell immunoglobulin-like receptor polymorphisms: their role in hematopoietic stem cell transplantation

Natural killer (NK) cells are important effector cells in the early control of infected, malignant, and "nonself" cells. Various receptor families are involved in enabling NK cells to detect and efficiently eliminate these target cells. The killer-cell immunoglobulin-like receptor (KIR) family is a set of receptors that are very polymorphic with regard to gene content, expression level, and expression pattern. KIRs are responsible for the induction of a NK cell alloreactive response through their interaction with HLA class I molecules. The role of NK cells in hematopoietic stem cell transplantation (HSCT) has been studied for many years, and induction of antileukemic responses by donor NK cells has been reported. Conflicting data still exist on the exact circumstances in which the KIR repertoire affects and influences clinical outcome after HSCT. More large-scale studies are needed on well-defined cohorts to unravel the mechanism of action of the NK cell-mediated alloresponse in an HSCT setting.

Absent CD56 expression in papillary thyroid carcinoma: A finding of potential diagnostic value in problematic cases of thyroid pathology

BACKGROUND

There are inter-observer disagreements between papillary thyroid carcinoma (PTC) with other follicular lesions of thyroid in aspect of diagnosis. CD56 is present on follicular epithelial cells of the normal thyroid. We evaluated the diagnostic value of CD56 expression in PTC, follicular thyroid lesions, and follicular thyroid neoplasms.

MATERIALS AND METHODS

Seventy-three cases diagnosed as follicular lesions and 73 cases diagnosed as PTC were stained with CD56 marker. A positive membranous immunostaining in more than 10% of the neoplastic cells qualified the case as "positive (+)" for CD56.

RESULTS

CD56 expression was seen in 70 samples of non-papillary carcinoma lesion (95.8%) versus one case of PTC (1.3%) (P < 0.001, Chi-square). Therefore, CD56 was 98.6% sensitive and 95.8% specific in distinguishing PTC from other follicular thyroid lesions.

CONCLUSION

CD56 is both a sensitive and specific marker for differentiating PTC from other follicular lesions of thyroid singly but it may be better to use a combination of markers for clinical evaluation of patients.

Bi(o)communications among peripheral blood fractions: a focus on NK and NKT cell biology in rheumatoid arthritis

Rheumatoid Arthritis (RA) is an autoimmune disease with unknown pathophysiology involving many interwoven signalling cascades. ROS, NK and NKT cells might be crucial in the disease severity of RA of which the role of NK and NKT cells are controversial in literature. However, the role of oxidative stress, its impact on NK and NKT cell immunobiology and disease activity (DAS28) is largely unknown. Therefore, we studied the role of oxidative stress and NK cell subsets in the pathogenesis of RA. The state of oxidative stress in various peripheral blood fractions, percentage NK and NKT cell expression, their altered apoptotic signaling pathways involving mitochondrial membrane potential, FAS associated death domain (FADD) mediated pathways and DNA damage were analyzed. Results indicated a state of profound oxidative stress in the peripheral blood of RA patients where percentage of NK and NKT cell subsets diminished while ROS levels increased. The depolarized mitochondrial membrane potential, FAS, FASL and active caspase-3 positive NK and NKT cell subsets were considerably elevated in patients. The DNA damage, assessed as percentage of DNA in comet tail, was significantly elevated. Findings of the present work indicate increased apoptosis of peripheral NK and NKT cells in the diseased condition. PBMC and RBC are the major sites of enhanced oxidative stress. The state of oxidative stress and altered immunobiology of NK and NKT cells strongly correlated with Disease activity score. The present study strongly supports the protective role of NK cell subsets in the pathogenesis of RA.

Higher NK cell IFN-γ production is associated with delayed HIV disease progression in LTNPs

Natural killer (NK) cells are important effectors of the innate immune system that help control viral infections and tumorigenesis. However, the relationship between NK cell function and HIV disease progression remains poorly defined. In this study, we examined the function of NK cells in Chinese patients who were HIV-infected but treatment-naïve. These individuals include primary HIV-infected patients (PHIs), typical progressors (TPs), and long-term nonprogressors (LTNPs). We observed an increase of CD56(dim) NK cells in PHIs, but the production of interferon-gamma (IFN-γ) and CD107a expression in PHIs were not altered compared with normal control subjects (NCs). However, the NK cells from LTNPs exhibited increased activities in IFN-γ production, CD107a expression and granzyme B change after K562 stimulation compared with NCs. Furthermore, the percentage of IFN-γ(+)CD107a(-) NK cells in LTNPs was higher than that in TPs, PHIs and NCs; levels of IFN-γ production in LTNP NK cells exhibited an inverse correlation with viral loads. Similar correlations, however, were not observed in the PHI and TP groups. Taken together, these data demonstrate that enhanced NK cell function may contribute to the control of HIV infection, and increased IFN-γ secretion may be associated with delayed disease progression.

Immunohistochemical markers in the diagnosis of papillary thyroid carcinomas: The promising role of combined immunostaining using HBME-1 and CD56

We aimed to evaluate the expression and diagnostic value of five immunohistochemical markers (HBME-1, Galectin-3, CK19, CD56 and p63) in a very large series of unequivocal papillary thyroid carcinoma (PTC) cases, including both the classic (CPTC) and the follicular variant (FVPTC). We performed an immunohistochemical analysis on a tissue micro-array of 204 PTCs (98 CPTCs, 90 FVPTCs, and 16 other variants). HBME-1 was the most sensitive marker, staining 95.9% of CPTCs and 81.1% of FVPTCs. CD56, a marker whose expression is reduced or absent in thyroid carcinoma, revealed a negative, "malignant" profile in 93.9% of CPTCs and 73.3% of FVPTCs. Galectin-3, CK19 and p63 were positive in 64.7%, 45.6% and 6.9% of PTCs, respectively. The immunopanel consisting of HBME-1, CD56 and/or CK19 reached the highest sensitivity (95.6%). The co-expression of 2 or more proteins was observed in 88.2% of PTCs, with HBME-1 and CD56 being the most frequent positive association (79.4%). We report a new panel of antibodies consisting of HBME-1, CK19 and CD56 that was found to be highly sensitive for both CPTC and FVPTC. This panel could be recommended as a supplement to the morphological criteria in the diagnosis of difficult FVPTC cases.

How I treat NK/T-cell lymphomas

Natural killer (NK)/T-cell lymphomas and NK-cell leukemias are aggressive malignancies. Occurring worldwide, they show a predilection for Asian and South American populations. Neoplastic cells are surface CD3-, cytoplasmic CD3ε+, CD56+, cytotoxic-molecule positive, Epstein-Barr virus (EBV) positive, with germline T-cell receptor gene. Lymphomas occur commonly in the nasal and upper aerodigestive region. Occasional cases present in the skin, salivary gland, testis, and gastrointestinal tract. Rare cases are disseminated with lymphadenopathy, hepatosplenomegaly, and a leukemic phase. Positron emission tomography computed tomography is useful in staging, as lymphomas are 18-fluorodeoxyglucose avid. Quantification of circulating EBV DNA is an accurate biomarker of tumor load. Nasal NK/T-cell lymphomas present mostly with stage I/II disease. Concomitant/sequential chemotherapy and radiotherapy is standard treatment. Radiotherapy alone is inadequate because of high systemic failure rate. For stage III/IV nasal, nonnasal, and disseminated lymphomas, systemic chemotherapy is indicated. Regimens containing l-asparaginase and drugs unaffected by P-glycoprotein are most effective. Hematopoietic stem cell transplantation (HSCT) is not indicated for early-stage nasal lymphomas. HSCT for lymphomas not in remission has poor results. In advanced-stage nasal, nonnasal, disseminated, or relapsed lymphomas, HSCT may be considered when remission is achieved. Prognostic modeling and EBV DNA monitoring may be useful in risk stratification for HSCT.

Immunosenescence and age-related viral diseases

Immunosenescence is described as a decline in the normal functioning of the immune system associated with physiologic ageing. Immunosenescence contributes to reduced efficacy to vaccination and increased susceptibility to infectious diseases in the elderly. Extensive studies of laboratory animal models of ageing or donor lymphocyte analysis have identified changes in immunity caused by the ageing process. Most of these studies have identified phenotypic and functional changes in innate and adaptive immunity. However, it is unclear which of these defects are critical for impaired immune defense against infection. This review describes the changes that occur in innate and adaptive immunity with ageing and some age-related viral diseases where defects in a key component of immunity contribute to the high mortality rate in mouse models of ageing.

Detection of the GD2+/CD56+/CD45- immunophenotype by flow cytometry in cerebrospinal fluids from a patient with retinoblastoma

Triple-color flow cytometry with a panel of antibodies comprising GD2, CD56, and CD45 was performed to analyze cerebrospinal fluids (CSF) from a patient with retinoblastoma who was suspicious of meningeal metastasis based on clinical presentation. Our results showed that the cells in CSF demonstrated the immunophenotype positive for GD2 and CD56 but negative for CD45 antigen, which suggested the presence of CSF metastasis of retinoblastoma. At the end of eight cycles of intrathecal chemotherapy, CSF specimen was analyzed with Flow cytometry immunophenotyping (FCI) again and the result showed no detectable malignant cells with the same immunophenotype. Our conclusion is that FCI can be a quick and reliable method for the diagnosis of CSF metastasis of retinoblastoma and the immunophenotype (GD2+, CD56+, and CD45-) can be used to recognize residual retinoblastoma cells in CSF.

Interleukin-15-induced CD56(+) myeloid dendritic cells combine potent tumor antigen presentation with direct tumoricidal potential

Dendritic cells (DCs) are the quintessential antigen-presenting cells of the human immune system and play a prime role in coordinating innate and adaptive immune responses, explaining the strong and still growing interest in their application for cancer immunotherapy. Much current research in the field of DC-based immunotherapy focuses on optimizing the culture conditions for in vitro DC generation in order to assure that DCs with the best possible immunogenic qualities are being used for immunotherapy. In this context, monocyte-derived DCs that are alternatively induced by interleukin-15 (IL-15 DCs) have attracted recent attention due to their superior immunostimulatory characteristics. In this study, we show that IL-15 DCs, in addition to potent tumor antigen-presenting function, possess tumoricidal potential and thus qualify for the designation of killer DCs. Notwithstanding marked expression of the natural killer (NK) cell marker CD56 on a subset of IL-15 DCs, we found no evidence of a further phenotypic overlap between IL-15 DCs and NK cells. Allostimulation and antigen presentation assays confirmed that IL-15 DCs should be regarded as bona fide myeloid DCs not only from the phenotypic but also from the functional point of view. Concerning their cytotoxic activity, we demonstrate that IL-15 DCs are able to induce apoptotic cell death of the human K562 tumor cell line, while sparing tumor antigen-specific T cells. The cytotoxicity of IL-15 DCs is predominantly mediated by granzyme B and, to a small extent, by tumor necrosis factor-α (TNF-α)-related apoptosis-inducing ligand (TRAIL) but is independent of perforin, Fas ligand and TNF-α. In conclusion, our data provide evidence of a previously unappreciated role for IL-15 in the differentiation of human monocytes towards killer DCs. The observation that IL-15 DCs have killer DC capacity lends further support to their implementation in DC-based immunotherapy protocols.

Potential diagnostic utility of CD56 and claudin-1 in papillary thyroid carcinoma and solitary follicular thyroid nodules

BACKGROUND AND AIM

The pathological diagnosis of papillary thyroid carcinoma (PTC) is usually easily achieved. However distinguishing the follicular variant of papillary carcinoma (FVPC) from other follicular thyroid lesions is an area of controversy. In this study we investigated the role of CD56 and claudin-1 in discriminating the FVPCs from other solitary follicular patterned nodules. We also evaluated the application of these two markers in reclassifying the controversial cases of the well differentiated tumors of unknown malignant potential (WDTs-UMP).

MATERIALS AND METHODS

The immunohistochemical expression of CD56 and claudin-1 was evaluated in 86 samples of thyroid lesions together with 10 samples of normal thyroid tissue. Thyroid lesions included: 29 PTCs [classic papillary carcinoma (n = 13) and FVPC (n = 16)], 47 solitary follicular patterned nodules [follicular adenomas (n = 12), hyperplastic nodules (n = 32) and follicular tumor of unknown malignant potential (n = 3)] and 10 WDTs-UMP.

RESULTS

The statistical analysis showed significantly different expressions of each of CD56 and claudin-1 in the FVPCs versus other solitary follicular patterned nodules. Claudin-1 sensitivity (100%) was higher than CD56 sensitivity (81.3%). However claudin-1 specificity (80.9%) was < CD56 specificity (89.4%). The combined use of CD56 and claudin-1(claudin-1 + /CD56-) showed specificity (100%), positive predictive value (100%) and sensitivity (81.3%) in the differentiation between the FVPCs and other follicular nodules. In the light of this statistical outcome, 5/10 cases of WDTs-UMP expressing the (claudin-1 + /CD56-) panel could be rediagnosed as PTC.

CONCLUSION

Combined utility of CD56 and claudin-1 is helpful in diagnosing the FVPC and its differentiation from other follicular patterned nodules. Application of these two markers may greatly aid in the reevaluation of the WDTs-UMP and interpretation of their expected behavior.

Increased expression and function of P-glycoprotein in peripheral blood CD56+ cells is associated with the chemoresistance of non-small-cell lung cancer

PURPOSE

Chemoresistance is common among non-small-cell lung cancer (NSCLC), P-glycoprotein (P-gp), encoded by the human multi-drug-resistant MDR1 gene, and multidrug-resistance protein 1 (MRP1) might be major contributors. The aim of the present study was to develop an effective method to investigate the expression and function of P-gp in the peripheral CD56+ cells in order to clarify their correlation with the chemoresistance in NSCLC.

METHODS

Using microbead technology and a RT-qPCR methodology, we evaluated the expression levels of P-gp and MRP1 in the purified CD56+ cells in the chemoresistance and chemo-naive NSCLC patients compared with that in the healthy volunteers. Flow cytometric analysis was used to investigate the changes of P-gp function in the CD56+ cells between the three cohorts.

RESULTS

The MDR1 gene expression was elevated markedly (twofold-tenfold), and P-gp function was increased in the chemoresistance cohort compared with the chemo-naive and the healthy cohorts; whereas there was only about two times averagely elevated for the MRP1 gene expression. No statistical significance (p > 0.05) was seen with respect to the expression of MDR1 and MRP1, the function of P-gp between the chemo-naive and the healthy cohorts.

CONCLUSIONS

P-gp in peripheral CD56+ cells demonstrated possible clinical relevance as predictive biomarkers for the identification of chemoresistance in NSCLC, while MRP1 may not play a significant role in the drug resistance in NSCLC. The potential applications for this finding are provided evidence to screen the potential P-gp reversors and to diagnose and manage the chemoresistance in NSCLC patients.

Generation of natural killer cells from hematopoietic stem cells in vitro for immunotherapy

Natural killer (NK) cells are part of the innate immune system and are an alluring option for immunotherapy due to their ability to kill infected cells or cancer cells without prior sensitization. Throughout the past 20 years, different groups have been able to reproduce NK cell development in vitro, and NK cell ontogeny studies have provided the basis for the establishment of protocols to produce NK cells in vitro for immunotherapy. Here, we briefly discuss NK cell development and NK cell immunotherapy approaches. We review the factors needed for NK cell differentiation in vitro, which stem cell sources have been used, published protocols, challenges and future directions for Good Manufacturing Practice protocols.

Extramedullary relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation: an easily overlooked but significant pattern of relapse

Acute myeloid leukemia may manifest as myeloid sarcoma in a variety of extramedullary (EM) tissues at diagnosis or at relapse. Although EM relapse after allogeneic hematopoietic stem cell transplantation (alloSCT) has been considered to be rare, recent studies have suggested that it occurs in 5% to 12% of patients who receive alloSCT, accounting for 7% to 46% of total relapses. The incidence of EM relapse after immunomodulation (eg, donor lymphocyte infusion) or a second SCT is even higher. Moreover, patients with EM relapse are more likely to have had preceding acute graft-versus-host disease or chronic graft-versus-host disease relative to those with bone marrow relapse. Collectively, these observations suggest that the preferential occurrence of the graft-versus-leukemia effect underlies the pathogenesis of EM relapse. Establishing an early diagnosis of EM relapse has been challenging because of the immense diversity in the relapse sites; however, recent studies have suggested the usefulness of (18)F-fluorodeoxyglucose positron emission tomography scans in the detection of EM relapse. As a treatment for EM relapse, a combination of local and systemic therapy should be considered, because local therapy alone often results in subsequent systemic relapse. The prognosis for patients who develop EM relapse after SCT remains poor but is slightly better than that after bone marrow relapse. In addition to an early diagnosis with new modalities, clinical studies using new agents that may offer systemic activity while preserving the graft-versus-leukemia effect are warranted as part of an effort to improve the clinical outcome.

The role of natural killer cells in hematopoietic stem cell transplantation

Natural killer (NK) cells are important elements of innate immunity, and a large body of evidence supports the significant role of NK in immune surveillance against infections and tumors. Regulation of cytotoxic activity is mediated through activating and inhibitory receptors expressed on the cell surface. NK cells are key players of allogeneic hematopoietic stem cell transplantation (allo-SCT), and previous studies showed the beneficial effect of NK alloreactivity in prevention of relapse, especially in the setting of haploidentical SCT. Biology of human NK cells is an area of active research. Exploitation of the molecular mechanisms regulating NK maturation, tolerance to self, and NK-mediated cytotoxicity will help in the development of innovative NK cell immunotherapy methods.

Endosialidases: Versatile Tools for the Study of Polysialic Acid

Polysialic acid is an α2,8-linked N-acetylneuraminic acid polymer found on the surface of both bacterial and eukaryotic cells. Endosialidases are bacteriophage-borne glycosyl hydrolases that specifically cleave polysialic acid. The crystal structure of an endosialidase reveals a trimeric mushroom-shaped molecule which, in addition to the active site, harbors two additional polysialic acid binding sites. Folding of the protein crucially depends on an intramolecular C-terminal chaperone domain that is proteolytically released in an intramolecular reaction. Based on structural data and previous considerations, an updated catalytic mechanism is discussed. Endosialidases degrade polysialic acid in a processive mode of action, and a model for its mechanism is suggested. The review summarizes the structural and biochemical elucidations of the last decade and the importance of endosialidases in biochemical and medical applications. Active endosialidases are important tools in studies on the biological roles of polysialic acid, such as the pathogenesis of septicemia and meningitis by polysialic acid-encapsulated bacteria, or its role as a modulator of the adhesion and interactions of neural and other cells. Endosialidase mutants that have lost their polysialic acid cleaving activity while retaining their polysialic acid binding capability have been fused to green fluorescent protein to provide an efficient tool for the specific detection of polysialic acid.

Ex vivo differentiation of natural killer cells from human umbilical cord blood CD34+ progenitor cells

Natural Killer (NK)-cells are peripheral blood lymphocytes that represent an important arm of the innate immune system. NK-cells play a critical role in the immune surveillance against tumors and virally infected cells in a major histocompatibiliy complex (MHC)-unrestricted fashion. We have explored such capacities of NK-cells after differentiation from hematopoietic stem and progenitor cells derived from human umbilical cord blood. Several culture conditions have been established supporting proliferation and subsequent differentiation of these cells in terms of receptor expression and specific lysis depending on the growth conditions in the presence and absence of supportive stromal feeders. We show that acquisition of Killer Immunoglobulin Receptor (KIR) as well as NK Cytotoxicity Receptor expressions is independent of culture condition whereas absence of stromal feeders did not support acquisition of CD94/NKG2A expression. Such KIR-positive/NKG2A-negative cells generated under different culture conditions showed strong and specific cytolytic activity which could have impact on further immunotherapeutic strategies.

NKp46 identifies an NKT cell subset susceptible to leukemic transformation in mouse and human

IL-15 may have a role in the development of T cell large granular lymphocyte (T-LGL) or NKT leukemias. However, the mechanisms of action and the identity of the cell subset that undergoes leukemic transformation remain elusive. Here we show that in both mice and humans, NKp46 expression marks a minute population of WT NKT cells with higher activity and potency to become leukemic. Virtually 100% of T-LGL leukemias in IL-15 transgenic mice expressed NKp46, as did a majority of human T-LGL leukemias. The minute NKp46+ NKT population, but not the NKp46⁻ NKT population, was selectively expanded by overexpression of endogenous IL-15. Importantly, IL-15 transgenic NKp46⁻ NKT cells did not become NKp46+ in vivo, suggesting that NKp46+ T-LGL leukemia cells were the malignant counterpart of the minute WT NKp46+ NKT population. Mechanistically, NKp46+ NKT cells possessed higher responsiveness to IL-15 in vitro and in vivo compared with that of their NKp46⁻ NKT counterparts. Furthermore, interruption of IL-15 signaling using a neutralizing antibody could prevent LGL leukemia in IL-15 transgenic mice. Collectively, our data demonstrate that NKp46 identifies a functionally distinct NKT subset in mice and humans that appears to be directly susceptible to leukemic transformation when IL-15 is overexpressed. Thus, IL-15 signaling and NKp46 may be useful targets in the treatment of patients with T-LGL or NKT leukemia.

Diagnosis and management of natural killer-cell malignancies

Natural killer (NK)-cell malignancies are uncommon neoplasms, which have been referred to as polymorphic reticulosis or angiocentric T-cell lymphomas in the past. In the current WHO classification, they are categorized as extranodal NK/T-cell lymphoma, nasal type and aggressive NK-cell leukemia. NK-cell malignancies show a geographical predilection for Asian and South American populations and are rare in the west. Pathologically, NK-cell lymphomas show a polymorphic neoplastic infiltrate with angioinvasion and angiodestruction. The lymphoma cells are CD2(+), cytoplasmic CD3ε(+) and CD56(+), with germline T-cell receptor gene. There is an almost invariable clonal episomal infection with Epstein-Barr virus. Clinically, NK-cell lymphomas can be classified into nasal, non-nasal and aggressive lymphoma/leukemia subtypes. Most nasal NK-cell lymphomas present with stage I/II disease. The early use of radiotherapy, either alone or concomitantly/sequentially with chemotherapy, is the most important factor in achieving successful treatment. Many stage I/II patients receiving radiotherapy alone fail systemically, so the use of chemotherapy is also considered necessary. Chemotherapy is indicated for stage III/IV nasal NK-cell lymphoma, and the non-nasal and aggressive subtypes. Recent regimens that incorporate the use of L-asparaginase have resulted in substantial improvements in outcome in high-risk, refractory or relapsed patients. High-dose chemotherapy and hematopoietic stem-cell transplantation with autologous or allogeneic hematopoietic stem cells may be beneficial to selected patients. Prognostication of patients with clinical prognostic models and presentation circulating Epstein-Barr DNA load may be useful in the stratification of patients for various treatment modalities.

NK cells and immune "memory"

Immunological memory is a hallmark of the adaptive immune system. However, the ability to remember and respond more robustly against a second encounter with the same pathogen has been described in organisms lacking T and B cells. Recently, NK cells have been shown to mediate Ag-specific recall responses in several different model systems. Although NK cells do not rearrange the genes encoding their activating receptors, NK cells experience a selective education process during development, undergo a clonal-like expansion during virus infection, generate long-lived progeny (i.e., memory cells), and mediate more efficacious secondary responses against previously encountered pathogens--all characteristics previously ascribed only to T and B cells in mammals. This review describes past findings leading up to these new discoveries, summarizes the evidence for and characteristics of NK cell memory, and discusses the attempts and future challenges to identify these long-lived memory NK cell populations in humans.

Uterine natural killer (uNK) cells and their missions during pregnancy: a review

Natural killer (NK) cells are lymphocytes of the innate immune system. The aim of this review is to describe the properties and roles of NK cells in the human uterus during pregnancy. Uterine natural killer cells (uNK) constitute a major lymphocyte population during early gestation in the uterus. The uterine natural killer cells are recognized owing to their CD56(bright), CD16(-), CD3(-) phenotype. Their number increases in the first trimester with a subsequent decline as pregnancy progresses. They have been shown to be closely associated with cells of the extravillous trophoblast (EVT) and spiral arteries. They play important roles in remodeling of the spiral arteries, control of trophoblast invasion and in the development of the placenta. Some studies have shown the number and repertoire of receptors of uNK differ between women with healthy pregnancies and those with pathologic pregnancies, such as pre-eclampsia or intrauterine growth retardation. During pregnancy, the cytotoxic characteristics of the uterine killer cells are not directed towards the fetus, and scientists continue to question and explore this phenomenon with increasing evidence that these cells may perform differing beneficial roles during pregnancy. Contrary to their previously suspected "hostile" characteristics, the uterine killer cells are considered to be "friendly" and appear to be essential and very important regulators of successful implantation and pregnancy.

Innate immune natural killer cells and their role in HIV and SIV infection

The findings that early events during HIV-1 and SIV infection of Asian rhesus macaques dictate the levels of viremia and rate of disease progression prior to the establishment of mature and effective adaptive immune responses strongly suggest an important role for innate immune mechanisms. In addition, the fact that the major target of HIV and SIV during this period of acute infection is the gastrointestinal tissue suggests that whatever role the innate immune system plays must either directly and/or indirectly focus on the GI tract. The object of this article is to provide a general overview of the innate immune system with a focus on natural killer (NK) cells and their role in the pathogenesis of lentivirus infection. The studies summarized include our current understanding of the phenotypic heterogeneity, the putative functions ascribed to the subsets, the maturation/differentiation of NK cells, the mechanisms by which their function is mediated and regulated, the studies of these NK-cell subsets, with a focus on killer cell immunoglobulin-like receptors (KIRs) in nonhuman primates and humans, and finally, how HIV and SIV infection affects these NK cells in vivo. Clearly much has yet to be learnt on how the innate immune system influences the interaction between lentiviruses and the host within the GI tract, knowledge of which is reasoned to be critical for the formulation of effective vaccines against HIV-1.

Identification of new populations of chicken natural killer (NK) cells

Natural killer (NK) cell activity is conserved throughout vertebrate development, but characterization of non-mammalian NK-cells has been hampered by the absence of specific mAbs for these cells. Monoclonal antibodies were generated against in vitro IL-2 expanded sorted CD3-CD8alpha+ peripheral blood lymphocytes, previously described to contain chicken NK-cells. Screening of embryonic and adult splenocytes with hybridoma supernatants resulted in five candidate NK markers. Activation of chicken NK-cells with PMA/Ionomycin or with the NK target cell-line LSCC-RP9 resulted in increased expression of CD107 (LAMP-1) and a newly developed flow cytometry based cytotoxicity assay showed that NK-cells were able to kill target cells. Combining NK markers with functional assays indicated that marker positive cells showed NK-cell function. In conclusion, we generated new monoclonal antibodies and developed two functional assays which will enhance our understanding of the role of NK-cells in healthy and diseased chickens.

Repertoire development and the control of cytotoxic/effector function in human gammadelta T cells

T cells develop into two major populations distinguished by their T cell receptor (TCR) chains. Cells with the alphabeta TCR generally express CD4 or CD8 lineage markers and mostly fall into helper or cytotoxic/effector subsets. Cells expressing the alternate gammadelta TCR in humans generally do not express lineage markers, do not require MHC for antigen presentation, and recognize nonpeptidic antigens. We are interested in the dominant Vgamma2Vdelta2+ T cell subset in human peripheral blood and the control of effector function in this population. We review the literature on gammadelta T cell generation and repertoire selection, along with recent work on CD56 expression and defining a cytotoxic/effector lineage within the phosphoantigen-reactive Vgamma2Vdelta2 cells. A unique mechanism for MHC-independent repertoire selection is linked to the control of effector function that is vital to the role for gammadelta T cells in tumor surveillance. Better understanding of these mechanisms will improve our ability to exploit this population for tumor immunotherapy.

CD56+ human blood dendritic cells effectively promote TH1-type gammadelta T-cell responses

CD56+ human dendritic cells (DCs) have recently been shown to differentiate from monocytes in response to GM-CSF and type 1 interferon in vitro. We show here that CD56+ cells freshly isolated from human peripheral blood contain a substantial subset of CD14+CD86+HLA-DR+ cells, which have the appearance of intermediate-sized lymphocytes but spontaneously differentiate into enlarged DC-like cells with substantially increased HLA-DR and CD86 expression or into fully mature CD83+ DCs in response to appropriate cytokines. Stimulation of CD56+ cells containing both DCs and abundant gammadelta T cells with zoledronate and interleukin-2 (IL-2) resulted in the rapid expansion of gammadelta T cells as well as in IFN-gamma, TNF-alpha, and IL-1beta but not in IL-4, IL-10, or IL-17 production. IFN-gamma, TNF-alpha, and IL-1beta production were almost completely abolished by depleting CD14+ cells from the CD56+ subset before stimulation. Likewise, depletion of CD14+ cells dramatically impaired gammadelta T-cell expansion. IFN-gamma production could also be blocked by neutralizing the effects of endogenous IL-1beta and TNF-alpha. Conversely, addition of recombinant IL-1beta, TNF-alpha, or both further enhanced IFN-gamma production and strongly up-regulated IL-6 production. Our data indicate that CD56+ DCs from human blood are capable of stimulating CD56+ gammadelta T cells, which may be harnessed for immunotherapy.

Utility of CD56 immunohistochemical studies in follow-up of plasma cell myeloma

Although 70% to 80% of plasma cell myelomas (PCMs) express CD56, few data are available on the usefulness of CD56 immunohistochemical analysis in assessing residual disease. We retrospectively reviewed 127 PCM posttreatment bone marrow (BM) specimens, classifying them as positive or negative for residual disease (independent of CD56 immunohistochemical studies) based on abnormal plasma cell (PC) morphologic features or flow cytometry (FC) and/or light chain restriction by immunohistochemical studies (conventional criteria). CD56 immunohistochemical analysis was performed on these and 20 negative lymphoma staging BM specimens. Of 127 BM specimens, 74 were positive and 53 were negative for residual PCM by conventional criteria. Of 74 BM specimens positive by conventional criteria, 59 (80%) demonstrated CD56 (strong+) PCs in clusters and/or with cytologic atypia. Of the 53 BM specimens negative by conventional criteria, 3 showed CD56 (strong+) morphologically atypical PCs in clusters or scattered. CD56 immunohistochemical analysis is useful for detecting residual PCM, particularly in morphologically equivocal cases in which light chain restriction cannot be demonstrated, and may serve as a potential response criterion.

New multiple labelling method for improved satellite cell identification in human muscle: application to a cohort of power-lifters and sedentary men

Presently applied methods to identify and quantify human satellite cells (SCs) give discrepant results. We introduce a new immunofluorescence method that simultaneously monitors two SC markers (NCAM and Pax7), the basal lamina and nuclei. Biopsies from power-lifters, power-lifters using anabolic substances and untrained subjects were re-examined. Significantly different results from those with staining for NCAM and nuclei were observed. There were three subtypes of SCs; NCAM(+)/Pax7(+) (94%), NCAM(+)/Pax7(-) (4%) and NCAM(-)/Pax7(+) (1%) but large individual variability existed. The proportion of SCs per nuclei within the basal lamina of myofibres (SC/N) was similar for all groups reflecting a balance between the number of SCs and myonuclei to maintain homeostasis. We emphasise that it is important to quantify both SC/N and the number of SCs per fibre. Our multiple marker method is more reliable for SC identification and quantification and can be used to evaluate other markers of muscle progenitor cells.

Role of NK and NKT cells in solid organ transplantation

In the context of solid organ transplantation, the exact interactions between the innate and adaptive alloimmune response have not yet been fully explored. In this transplant setting, natural killer (NK) cells have emerged as a particular focus of interest because of their ability to distinguish allogeneic major histocompatibility complex (MHC) antigens and their potent cytolytic activity. Based on this observation and its potential clinical relevance, NK cells have recently been shown to participate in the immune response in both acute and chronic rejection of solid organ allografts. Numerous experimental and clinical studies demonstrate that NK cells determine transplant survival by rejecting an allograft not directly but indirectly by providing bystander effects. In addition, NK cells are influenced by immunosuppressive therapies such as calcineurin inhibitors or steroids. As NK and natural killer T (NKT) cells have also been shown to play a profound role in allograft tolerance induction, this review summarizes the major findings to highlight the functional role of these lymphocyte subsets, which may constitute an underestimated mechanism affecting graft outcome in solid organ transplantation.

Diagnostic utility of CD56 immunohistochemistry in papillary carcinoma of the thyroid

Diagnosis of papillary thyroid carcinoma (PTC), in many but not all cases, is an easily achievable diagnosis with almost minimal interobservable variability between pathologists. However, some cases of PTC, particularly the follicular variant, are quite challenging and show wide interobservable variability even among expert thyroid pathologists. Since proper diagnosis of PTC is crucial as it affects patients' clinical management and prognosis, indications of PTC must be clearly apparent to be an objective rather than a subjective diagnosis. Unfortunately, to date, immunohistochemistry and molecular studies have failed to fully solve this problem. In this study, we assessed the protein expression and loss using antibodies against CD56 in normal follicular thyroid epithelium, follicular thyroid lesions, and follicular thyroid neoplasms in an attempt to evaluate its diagnostic value. A total of 185 cases were studied with tissues from 75 carcinomas (72 papillary, 2 follicular, 1 Hürthle cell) and 35 adenomas (32 follicular and 3 Hürthle cell) evaluated by immunohistochemistry for the expression of this marker. Non-neoplastic thyroids included 65 cases: nodular hyperplasia (n=25), thyrotoxic hyperplasia (Grave's disease) (n=5), lymphocytic thyroiditis (n=19), and Hashimoto's thyroiditis (n=6). Ten cases of normal thyroids from radical laryngectomies for laryngeal squamous cell carcinomas were also studied. The marker pattern and intensity of staining were scored. Positive expression of the markers in 10% or more of follicular epithelium within the tumor or lesional cells was considered positive. An expression of <10% was considered to be negative. Diffuse CD56 expression was consistently present in normal, lesional, and neoplastic follicular epithelium, except for PTC, including the follicular variant. We concluded that CD56 is of value to distinguish PTC from other thyroid follicular pathology/histology with a sensitivity of 100% and a specificity of 100%. We suggest that CD56 is extremely useful in the diagnosis of PTC, including the follicular variant, and to distinguish it from other follicular cell-derived thyroid tumors/lesions. Application of CD56 by a group of expert pathologists on a larger series of follicular thyroid neoplasms of uncertain malignant potentials may potentially provide an objective diagnostic tool.

Polysialic acid, a glycan with highly restricted expression, is found on human and murine leukocytes and modulates immune responses

Polysialic acid (polySia) is a large glycan with restricted expression, typically found attached to the protein scaffold neural cell adhesion molecule (NCAM). PolySia is best known for its proposed role in modulating neuronal development. Its presence and potential functions outside the nervous systems are essentially unexplored. Herein we show the expression of polySia on hematopoietic progenitor cells, and demonstrate a role for this glycan in immune response using both acute inflammatory and tumor models. Specifically, we found that human NK cells modulate expression of NCAM and the degree of polymerization of its polySia glycans according to activation state. This contrasts with the mouse, where polySia and NCAM expression are restricted to multipotent hematopoietic progenitors and cells developing along a myeloid lineage. Sialyltransferase 8Sia IV(-/-) mice, which lacked polySia expression in the immune compartment, demonstrated an increased contact hypersensitivity response and decreased control of tumor growth as compared with wild-type animals. This is the first demonstration of polySia expression and regulation on myeloid cells, and the results in animal models suggest a role for polySia in immune regulation.

Differentiation potential of human muscle-derived cells towards chondrogenic phenotype in alginate beads culture

OBJECTIVE

The aim of this study was to evaluate the differentiation potential of two populations of muscle-derived cells (CD56- and CD56+) towards chondrogenic phenotype in alginate beads culture and to compare the effect of transforming growth factor beta 1 (TGFbeta1) on the differentiation process in these populations.

METHODS

Muscle CD56- and CD56+ cells were cultured in alginate beads, in a chondrogenic medium, containing or not TGFbeta1 (10 ng/ml). Cultures were maintained for 3, 7, 14 or 21 days in a humidified culture incubator. At harvest, one culture of each set was fixed for alcian blue staining and aggrecan detection. The steady-state level of matrix macromolecules mRNA was assessed by real-time polymerase chain reaction (PCR). Protein detection was performed by western-blot analysis. The binding activity of nuclear extracts to Cbfa1 DNA sequence was also evaluated by electrophoretic mobility shift assays (EMSA).

RESULTS

Chondrogenic differentiation of both CD56+ and CD56- muscle-derived cells was improved in alginate scaffold, even without growth factor, as suggested by increased chondrogenesis markers expression during the culture. Furthermore, TGFbeta1 enhanced the differentiation process and allowed to maintain a high expression of markers of mature chondrocytes. Of importance, the combination of alginate and TGFbeta1 treatment resulted in a further down-regulation of collagen type I and type X, as well as Cbfa1 both expression and binding activity.

CONCLUSIONS

Thus, alginate scaffold and chondrogenic medium are sufficient to lead both populations CD56+ and CD56- towards chondrogenic differentiation. Moreover, TGFbeta1 enhances this process and allows to maintain the chondrogenic phenotype by inhibiting terminal differentiation, particularly for CD56- cells.

Generation of monoclonal antibody against canine neural-cell adhesion molecule

A monoclonal antibody, K9BYU, was generated using Escherichia coli recombinant extracellular domain of canine neural-cell adhesion molecule (N-CAM) as an antigen. Immunoreactivity of K9BYU to insect cell recombinant canine N-CAM was demonstrated by Western blotting using Sf9 insect cells transfected with the canine N-CAM gene. In Western blotting against canine brain tissue, K9BYU detected three isoforms of N-CAM that correspond to three major isoforms of human and mouse N-CAM (N-CAM-120, -140, and -180). From these results, K9BYU was considered to be a useful tool for research of canine N-CAM.

Genetic changes in small cell lung carcinoma

Small cell lung carcinoma (SCLC) accounts for approximately 15% of all lung cancer cases. Despite a frequently good response to first-line treatment with chemotherapy and/or radiotherapy, early relapse occurs in the majority of patients and 5-year survival is only about 5%. Therefore, there is a need to develop novel treatments to improve the outcome of patients with SCLC. To fulfil this need, it is critical to gain further understanding on the molecular basis of SCLC and specifically to identify novel therapeutic targets. Clinical trials with molecularly targeted agents have been performed with little success in the past, but recently many promising oncogenic pathways have been discovered and novel targeted therapies are under evaluation. In this review, we summarise the most relevant genetic and signalling pathway alterations reported to date in SCLC and discuss the potential therapeutic implications of such events.

Human natural killer cells

Natural killer (NK) cells were discovered more than 30 years ago. NK cells are large granular lymphocytes that belong to the innate immune system because unlike T or B lymphocytes of the adaptive or antigen-specific immune system, NK cells do not rearrange T-cell receptor or immunoglobulin genes from their germline configuration. During the past 2 decades there has been a substantial gain in our understanding of what and how NK-cells "see," lending important insights into their functions and purpose in normal immune surveillance. The most recent discoveries in NK-cell receptor biology have fueled translational research that has led to remarkable results in treating human malignancy.

NK cells and their receptors

Despite early reports that natural killer (NK) cells are non-specific or have non-major histocompatibility complex (MHC)- restricted killing, it is now clear that NK cells express a panoply of receptors with defined specificity for ligands expressed on their cellular targets. The roles of these receptors in terms of physiological NK cell effector functions, such as cytotoxicity and cytokine production, are beginning to be unravelled. Inasmuch as NK cells accumulate in the uterus, an appreciation of NK cell receptor specificities and their physiological functions should provide valuable clues to the role of NK cells in the uterus and during pregnancy.

Application of CD56, P63 and CK19 immunohistochemistry in the diagnosis of papillary carcinoma of the thyroid

Papillary carcinoma of the thyroid (PTC) is the commonest thyroid cancer. In the recent decades an obvious increase in the incidence of PTC has occurred. The pathological diagnosis of PTC is usually an easy diagnosis in the majority of cases. However since the introduction of follicular variant of PTC and the wide threshold range in interpretation of the clearly set pathological criteria for diagnosis of PTC, between pathologists including experts, the diagnosis in some cases became quite difficult. Unfortunately some cases are unjustifiably over-called as follicular variant of PTC as a result of the wide inter observable variability between pathologists, including thyroid pathologists.

Ancillary studies such as immmunohistochemistry may be helpful, but till now there is no 100% consistent marker(s), that distinct between PTC and other follicular thyroid lesions and tumors.

We assessed expression of antibodies against CD56, CK19, P63 and E-Cadherin in PTC and other follicular thyroid lesions and neoplasms. A total of 175 cases were studied. The neoplastic cases included 75 carcinomas (72 papillary, 2 follicular, 1 Hurthle cell) and 35 adenomas (32 follicular and 3 Hurthle cell). The non-neoplastic thyroids included 65 cases, (25 nodular hyperplasia, 5 thyrotoxic hyperplasia (Grave's disease), 19 lymphocytic thyroiditis and 6 Hashimoto's thyroiditis). All cases were evaluated by immunohistochemistry for the expression of the above mentioned markers. The markers' patterns and intensities of staining were scored. Positive expression of the markers equal or >10% of the follicular epithelium within the tumor or lesional cells was considered positive. An expression of <10% was considered to be negative.

Our results showed CD56 positive in all the lesions and tumors except for PTC in all cases (100%). CD56 was negative in all PTC cases (100%). CK 19 showed positive expression in PTC accounting for 85% of cases and in 26% of non PTC lesions/tumors. P63 showed selective focal positivity in PTC cases, in contrast to other non PTC lesions/tumors. P63 expression was in 70% of cases of PTC and was consistently absent in all the non PTC cases. E-Cadherin showed consistent non discriminatory expression in all cases included in the study.

We concluded that a panel consisted of CD56, CK19 and P63 is of value in distinction of PTC from other thyroid follicular lesion. P63 is a specific but less sensitive marker for PTC than CK19. CD56 is more specific and sensitive marker than CK19, however it is a negative rather than a positive marker for PTC. E-Cadherin is of no value in the diagnosis of thyroid follicular lesions/tumors. We recommend application of a panel composed of CK19, P63 and CD56 by a group of expert thyroid pathologists on a large series of follicular malignant thyroid neoplasms of uncertain malignant.

Humanized immune system (HIS) mice as a tool to study human NK cell development

The study of human hematopoiesis is conditioned by access to nondiseased human tissue samples that harbor the cellular substrates for this developmental process. Technical and ethical concerns limit the availability to tissues derived from the fetal and newborn periods, while adult samples are generally restricted to peripheral blood. Access to a small animal model that faithfully recapitulates the process of human hematopoiesis would provide an important tool. Natural killer (NK) cells comprise between 10% and 15% of human peripheral blood lymphocytes and appear conserved in several species. NK cells are implicated in the recognition of pathogen-infected cells and in the clearance of certain tumor cells. In this chapter, we discuss NK cell developmental pathways and the use of humanized murine models for the study of human hematopoiesis and, in particular, human NK cell development.

Distribution of neural cell adhesion molecule (NCAM/CD56) in gastrointestinal stromal tumours and their intra-abdominal mesenchymal mimics

Background:

The distribution and reactivity pattern of neural cell adhesion molecule (NCAM/CD56) in gastrointestinal stromal tumours (GISTs) and their mesenchymal mimics have not been investigated in the KIT era.

Methods:

275 histologically and immunohistochemically well characterised primary and metastatic intra-abdominal mesenchymal lesions were analysed by conventional immunohistochemistry, with emphasis on GIST and GI smooth muscle neoplasms.

Results:

CD56 expression was seen in 18/21 (86%), 4/5 (80%), 26/34 (76%), and 32/168 (19%) of primary GI leiomyomas, schwannomas, leiomyosarcomas, and GISTs, respectively. Reactivity in GISTs was mostly focal. Of 6% strongly staining GISTs, 71% were either malignant clinically or assigned a high risk prognostic group. CD56 expression in GISTs varied greatly with histological type (seen in 50% and 7% of epithelioid and spindled GISTs, respectively) and anatomical site (in 33%, 10%, 1%, and 0% of rectal, gastric, small intestinal and oesophageal GISTs, respectively). A variable, but inconsistent expression was seen in miscellaneous lesions including dedifferentiated liposarcoma, abdominopelvic PEComa, myo/fibroblastic sarcoma and malignant fibrous histiocytoma. Mesenteric fibromatoses, angiosarcoma/Kaposi sarcoma, reactive tumefactive fibrogenic lesions and 12/13 primary anorectal and oesophageal melanomas were negative.

Conclusion:

Results confirmed the ubiquity and non-specificity of CD56 as a neurogenic marker. Except for a subset of epithelioid gastric and high-grade rectal GISTs, CD56 expression is rare in GISTs, contrasting with true leiomyomatous and neurogenic neoplasms. CD56 plays a limited role in the differential diagnosis of GIST. Its potential role as a marker of adverse outcome in GISTs remains to be further investigated.