Expression of markers shared between human natural killer cells and neuroblastoma lines

Channel catfish NK-like cells are armed with IgM via a putative FcmicroR

Two-color flow cytometry demonstrated that 4-8% of channel catfish PBL are positive for both F and G IgL chain isotypes, suggesting that they passively acquire serum IgM via a putative FcmicroR. These cells show spontaneous killing toward allogeneic targets, and in vitro stimulation of PBL with allogeneic cells results in an increase of double IgL chain positive cells with a concomitant increase in nonspecific cytotoxicity. Long-term cultures of alloantigen-stimulated PBL contain both sIgM(+) and sIgM(-) cytotoxic cells that transcribe message for the catfish homolog of the FcepsilonR gamma chain, but not for Igmicro and TCR-alpha,-beta, or -gamma chains. Immunoprecipitation of lysates from sIgM(+) NK-like cells with anti-IgM co-immunoprecipitated a putative FcmicroR of approximately 64 kDa. Finally, removal of IgM from sIgM(+) NK-like cells and replacement with anti-hapten antibody enabled antibody-armed effectors to kill haptenated targets that were refractory to killing by effectors armed with normal IgM. This is the first report suggesting that teleost NK-like cells express a putative FcmicroR which participates in antibody-dependent cell-mediated cytotoxicity.

Therapeutic activity of NK cells against tumors

While it is generally accepted that natural killer (NK) cells, by killing tumor cells in the circulation, represent a first line of defense against metastases, their therapeutic activity against established tumors has been limited. In this review, we describe studies to improve the therapeutic effectiveness of activated NK cells in both animal models and clinical trials to better understand the biological problems that limit their effectiveness.

Origin and functions of human natural killer cells

Recent data have substantially modified our view of natural killer cells. Although maturation of natural killer cells occurs in the absence of a functional thymus, we have shown that clonogenic precursors capable of differentiating into mature CD3-16+56+ natural killer cells exist in CD3-4-8-16- populations isolated from human thymus. Analysis of peripheral blood-derived natural killer clones showed that they can lyse normal cells (e.g., phytohemagglutinin-induced blasts) isolated from some individuals. Importantly, natural killer clones isolated from single individuals displayed different patterns of cytolytic activity against a panel of normal allogeneic cells. These data suggested the existence of a natural killer cell repertoire. A number of observations have revealed that the expression of given HLA class I alleles protects target cells from lysis by different groups of natural killer clones. Evidence has been gained by genetic analysis of the determinants responsible for susceptibility/resistance to lysis by natural killer clones together with analysis, as target cells, of HLA-defective variants or HLA transfectants. Thus, natural killer cells were found to express a clonally distributed ability to recognize HLA class I alleles. The selection of new monoclonal antibodies directed against members of a novel family of natural killer specific p58 molecules allowed the identification of the putative natural killer receptors for different MHC class I alleles. Firstly, a correlation was established between the expression of given p58 molecules (e.g., EB6 and GL183) and the class I alleles recognized. Secondly, anti-p58 monoclonal antibodies restored the natural killer-mediated lysis of class I-protected cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny, specific functions and receptors of human natural killer cells

Several of the generally accepted ideas on natural killer (NK) cells have been challenged by recent data that have substantially modified our view on these lymphoid cell populations. Although maturation of NK cells can occur in the absence of a functional thymus, clonogenic precursors capable of differentiating into mature CD3-16+56+ NK cells were found in CD3-4-8-16- populations isolated from human postnatal thymus. Analysis of the cytolytic activity of interleukin-2-activated NK cell populations and clones revealed that they can lyse normal cells (e.g., PHA blasts) isolated from certain individuals. In addition, NK clones isolated from single donors displayed different patterns of cytolytic activity against a panel of allogeneic cells, thus indicating that an NK cell repertoire exists. Genetic analyses of the determinants responsible for susceptibility/resistance to lysis together with the use of HLA-defective variants or HLA-transfectants revealed that the expression of given HLA class I alleles protects target cells from lysis by different groups of NK clones. Thus, NK cells express a clonally distributed ability to recognize HLA class I alleles. New monoclonal antibodies directed to members of a novel family of NK-specific p58 molecules allowed identification of the putative NK receptors for different major histocompatibility complex class I alleles. Indeed, a precise correlation has been established between expression of given p58 molecules (e.g., EB6 and GL183 molecules) and class I alleles recognized. In addition, anti-p58 monoclonal antibodies restored the NK-mediated lysis of class I-protected cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue reactivity of anti-Leu19

Monoclonal antibody anti-Leu19, is a marker of natural killer cells. Since reactivity between anti-Leu7, another natural killer cell marker, and small cell neuroendocrine carcinomas has been described, we evaluated the reactivity of anti-Leu19 in 92 neuroendocrine tumours. Frozen sections in each case were immunostained using the avidin-biotin-peroxidase complex method with monoclonal anti-Leu19. We found Leu19 expression in 93% of the cases. We also evaluated 149 other tumours, including adenocarcinomas, undifferentiated large cell carcinomas, lymphomas, melanomas and soft tissue tumours. We found Leu19 expression in 36% (by liberal interpretative criteria), or 29% (by conservative interpretative criteria) of these cases. Thus, while anti-Leu19 appears to be a sensitive marker for neuroendocrine tumours, a lack of specificity limits its practical application in diagnostic histopathology.

Expression of CD56 (NKH-1) differentiation antigen in human thyroid epithelium

Leu-19 (CD56) MoAb is well known to recognize gp220 expressed on natural killer (NK) cells and is widely used as a NK cell marker. The expression of CD56 antigen was tested by means of sensitive alkaline phosphatase-anti-alkaline phosphatase (APAAP) immunohistochemical technique and the above mentioned MoAb as a primary antibody, on frozen sections of various fresh human tissues. Out of 11 organs examined only thyroid gland provided a distinct reaction confined to cell membranes of epithelial follicular cells. The reaction had a diffuse pattern in cases of Graves' disease and colloidal goitre while in Hashimoto's thyroiditis presented as a focal pattern. Other anti-NK cell MoAbs such as VD4 (CD16) and Leu-7 (CD57) reacted only with single cells of thyroid stroma. The results of APAAP staining were confirmed by the cytofluorimetric assessment of isolated thyroid cells. It is speculated that CD56 expression on thyroid cells may have a functional significance, perhaps related to neural-endocrine interactions.

Cross-reactivity of monoclonal antibody Leu-19 with some neuroectodermal and other non-immune tissues

Leu-19 antigen is a 200-220 kDa surface glycoprotein, initially detected on natural killer (NK) cells exhibiting non-major histocompatibility complex-restricted cytotoxicity. Using a monoclonal antibody (mAb) directed against the Leu-19 molecule, we were unable to identify NK cells immunohistologically in cryostat sections of neuroectodermal tumors. Instead, mAb Leu-19 cross-reacted with the surfaces of the tumor cells, except for melanomas. It stained mesodermal tumor cells less intensely and did not stain those of carcinoma metastases. In three plasmacytomas, cells were observed, most likely NK cells, which extend Leu-19-positive cell processes towards to the unstained tumor cells. Furthermore, the Leu-19 antigen was identified on physiological tissues, especially on all neuroendocrine cells analyzed. The cross-reactions observed with Leu-19 mAb were confirmed using mAb NKH-1, which is also directed against the Leu-19 molecule. Thus, the expression of Leu-19 on neuroectodermal cells is another example of antigen sharing between specialized immune cells and the nervous system.

Neuroblastoma and other childhood neural tumors: a review

Neuroblastoma is the most common nonhematopoietic solid tumor of childhood and has been intensively studied for at least 4 decades. Despite this, few predictive histopathologic clues to its behavior exist. Age, anatomic sites of occurrence, and clinical stage have traditionally been the only reliable prognostic factors in this disease. A number of laboratory studies that focus on biologic features such as neurotransmitter synthesis (adrenergic and noradrenergic catecholamines), neurotransmitter enzyme expression (dopamine beta hydroxylase, choline acetyl transferase), cytogenetics (homogeneously staining regions, double minute chromosomes, chromosome 1p deletions), molecular genetics (N-myc oncogene amplification and expression), and immunophenotype (surface epitopes such as HLA antigens and GD2 ganglioside and intracytoplasmic determinants such as neurofilament protein, synaptophysin, chromogranin, and neuron specific enolase) now enable the pathologist to predict clinical course in many cases and to distinguish bona fide neuroblastomas, regardless of age, site, or histologic appearance, from a host of related but distinctly separate neuroectodermal tumor entities with apparent different histogenesis, treatment sensitivity, and prognosis.

Biology of natural killer cells

Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.