Arylsulfatase in natural killer cells: its possible role in cytotoxicity

Ecotoxicological effects and bioaccumulation of BPA analogues and their mixture in the clam Ruditapes philippinarum

Bisphenol A is recognized as an endocrine disruptor that can affect several biological processes in marine species. Consequently, its use has been restricted and it has been replaced with other similar compounds named bisphenol A analogues (BPA analogues). BPA analogues are speculatively considered safer compounds than BPA and their usage is increasing with a consequent higher environmental release. In this study, specimens of the clam Ruditapes philippinarum were exposed to three main BPA analogues, namely BPAF, BPF, BPS and their mixture at an environmentally relevant concentration of 300 ng/L for 7 and 14 days. Effects on biomarkers indicative of cytotoxicity, oxidative stress and damage and neurotoxicity were evaluated. In addition, bioaccumulation of the compound tested was analysed in clam soft tissues. Results showed that BPA analogues at an environment concentration affected cellular parameters and antioxidant system causing also oxidative damage, suggesting that BPA analogues can be harmful compounds for clams.

Specific Antiproliferative Properties of Proteinaceous Toxin Secretions from the Marine Annelid Eulalia sp. onto Ovarian Cancer Cells

As Yondelis joins the ranks of approved anti-cancer drugs, the benefit from exploring the oceans' biodiversity becomes clear. From marine toxins, relevant bioproducts can be obtained due to their potential to interfere with specific pathways. We explored the cytotoxicity of toxin-bearing secretions of the polychaete Eulalia onto a battery of normal and cancer human cell lines and discovered that the cocktail of proteins is more toxic towards an ovarian cancer cell line (A2780). The secretions' main proteins were identified by proteomics and transcriptomics: 14-3-3 protein, Hsp70, Rab3, Arylsulfatase B and serine protease, the latter two being known toxins. This mixture of toxins induces cell-cycle arrest at G2/M phase after 3h exposure in A2780 cells and extrinsic programmed cell death. These findings indicate that partial re-activation of the G2/M checkpoint, which is inactivated in many cancer cells, can be partly reversed by the toxic mixture. Protein-protein interaction networks partake in two cytotoxic effects: cell-cycle arrest with a link to RAB3C and RAF1; and lytic activity of arylsulfatases. The discovery of both mechanisms indicates that venomous mixtures may affect proliferating cells in a specific manner, highlighting the cocktails' potential in the fine-tuning of anti-cancer therapeutics targeting cell cycle and protein homeostasis.

Shotgun proteomics of coelomic fluid from the purple sea urchin, Strongylocentrotus purpuratus

The purple sea urchin has a complex immune system that is likely mediated by gene expression in coelomocytes (blood cells). A broad array of potential immune receptors and immune response proteins has been deduced from their gene models. Here we use shotgun mass spectrometry to describe 307 proteins with possible immune function in sea urchins including proteins involved in the complement pathway and numerous SRCRs. The relative abundance of dual oxidase 1, ceruloplasmin, ferritin and transferrin suggests the production of reactive oxygen species in coelomocytes and the sequestration of iron. Proteins such as selectin, cadherin, talin, galectin, amassin and the Von Willebrand factor may be involved in generating a strong clotting reaction. Cell signaling proteins include a guanine nucleotide binding protein, the Rho GDP dissociation factor, calcium storage molecules and a variety of lipoproteins. However, based on this dataset, the expression of TLRs, NLRs and fibrinogen domain containing proteins in coelomic fluid and coelomocytes could not be verified.

Self-glycolipids modulate dendritic cells changing the cytokine profiles of committed autoreactive T cells

The impact of glycolipids of non-mammalian origin on autoimmune inflammation has become widely recognized. Here we report that the naturally occurring mammalian glycolipids, sulfatide and β-GalCer, affect the differentiation and the quality of antigen presentation by monocyte-derived dendritic cells (DCs). In response to sulfatide and β-GalCer, monocytes develop into immature DCs with higher expression of HLA-DR and CD86 but lower expression of CD80, CD40 and CD1a and lower production of IL-12 compared to non-modulated DCs. Self-glycolipid-modulated DCs responded to lipopolysaccharide (LPS) by changing phenotype but preserved low IL-12 production. Sulfatide, in particular, reduced the capacity of DCs to stimulate autoreactive Glutamic Acid Decarboxylase (GAD65) - specific T cell response and promoted IL-10 production by the GAD65-specific clone. Since sulfatide and β-GalCer induced toll-like receptor (TLR)-mediated signaling, we hypothesize that self-glycolipids deliver a (tolerogenic) polarizing signal to differentiating DCs, facilitating the maintenance of self-tolerance under proinflammatory conditions.

Structure and biogenesis of lytic granules

Lytic granules are specialized secretory organelles which appear after activation of CTLs and NK cells. The lytic granules contain a series of proteins that mediate target cell destruction after secretion from the cell. In addition, these organelles serve as the lysosomes of these lymphocytes. At the EM level three types of granules with distinct regions are distinguished. Intriguingly, lytic and lysosomal proteins are localized in distinct regions. This is particularly interesting because lysosomal and lytic proteins can use the same sorting mechanisms to be targeted to this compartment. We favor the idea that a combination of sorting mechanisms result in this final segregation: the MPR receptor sorts both lysosomal proteins and granzymes from the Golgi complex, but a second event, such as selective aggregation with proteoglycans, then results in the segregation of lytic and lysosomal proteins in the granule. Lytic granules provide a way to store and simultaneously secrete the lytic proteins in a highly specific fashion. The granules are able to move along microtubules using a kinesin-like motor, and thus can cluster at the site of membrane contact with a target cell. Once polarized, the granules exocytose their contents, using a molecular machinery that is as yet poorly defined. Understanding the machinery involved in both functions of the lytic granules will provide ways to control the action of cytotoxic lymphocytes, ultimately in clinical situations.

Granzymes A and B are targeted to the lytic granules of lymphocytes by the mannose-6-phosphate receptor

To investigate the question of whether lytic granules share a common biogenesis with lysosomes, cloned cytolytic T cell lines were derived from a patient with I-cell disease. The targeting of two soluble lytic granule components, granzymes A and B, was studied in these cells which lack a functional mannose-6-phosphate (Man-6-P) receptor-mediated pathway to lysosomes. Using antibodies and enzymatic substrates to detect the lytic proteins, I-cells were found to constitutively secrete granzymes A and B in contrast to normal cells in which these proteins were stored for regulated secretion. These results suggest that granzymes A and B are normally targeted to the lytic granules of activated lymphocytes by the Man-6-P receptor. In normal cells, the granzymes bear Man-6-P residues, since the oligosaccharide side chains of granzymes A and B, as well as radioactive phosphate on granzyme A from labeled cells, were removed by endoglycosidase H (Endo H). However, in I-cells, granzymes cannot bear Man-6-P and granzyme B acquires complex glycans, becoming Endo H resistant. Although the levels of granzymes A and B in cytolytic I-cell lymphocytes are < 30% of the normal levels, immunolocalization and cell fractionation of granzyme A demonstrated that this reduced amount is correctly localized in the lytic granules. Therefore, a Man-6-P receptor-independent pathway to the lytic granules must also exist. Cathepsin B colocalizes with granzyme A in both normal and I-cells indicating that lysosomal proteins can also use the Man-6-P receptor-independent pathway in these cells. The complete overlap of these lysosomal and lytic markers implies that the lytic granules perform both lysosomal and secretory roles in cytolytic lymphocytes. The secretory role of lytic granules formed by the Man-6-P receptor-independent pathway is intact as assessed by the ability of I-cell lymphocytes to lyse target cells by regulated secretion.

Localization of lysosomal antigens in activated T-lymphocytes

The lysosomal compartment has been examined in activated T-lymphocytes by immunogold electron microscopy and subcellular fractionation. Immunoprecipitation and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of radiolabelled extracts of the T-cells showed that they contained three antigens which are fundamental to normal lysosomal function: a representative lysosomal enzyme beta-glucuronidase, a lysosomal associated membrane protein (LAMP-1), and the cation-independent mannose 6-phosphate lysosomal enzyme targeting receptor (MPR). Immunogold labelling showed that beta-glucuronidase was present in the rough endoplasmic reticulum, the Golgi complex and Golgi-associated vesicles. The enzyme was also found to accumulate in distinct, non-Golgi organelles in which LAMP-1 was co-localized, probably lysosomes. LAMP-1 was also found in tubular elements of the Golgi and in a complex of vesicles clustered near the nucleus where MPR was also present at high density. Fractionation of homogenates from lymphocytes on Percoll gradients revealed that beta-glucuronidase was distributed throughout the low density region containing rough endoplasmic reticulum, Golgi and plasma membrane components, and the high density region which contained only lysosomal activity. Multiple immunogold electron microscopy of the latter fraction showed the presence of homogenous vesicles which had large amounts of beta-glucuronidase within the lumen, LAMP-1 at the periphery and no MPR. These vesicles were probably mature lysosomes, arising from pre-lysosomal organelles enriched for LAMP-1 and MPR.

Macrophage membrane glycoproteins that bind Griffonia simplicifolia I-B4: effect on cytotoxicity and protein secretion

Thioglycollate elicited peritoneal (TG-Møs) but not resident peritoneal Møs (R-Møs) were found to bind the lectin Griffonia simplicifolia isotype I-B4 (GSI-B4). This was demonstrated by ultrastructural studies and FACS analyses. Membranes from TG-Møs were isolated, separated on SDS-PAGE, electrotransferred onto nitrocellulose, and exposed to peroxidase-labeled GSI-B4. These procedures revealed two major membrane glycoproteins of molecular weights 180,000 and 94,000 daltons that bound the lectin GSI-B4 which has a specificity for recognizing terminal alpha-galactosyl residues. The presence of these epitopes on the two membrane glycoproteins was further substantiated by the fact that treatment of the membranes with alpha-galactosidase destroyed their capacity to bind GSI-B4 and that alpha-D-galactopyranoside but not N-acetyl-D-glucosamine competitively inhibited GSI-B4 from binding to the glycoproteins. Treatment of TG-Møs with GSI-B4 reduced the capacity of interferon (IFN) and lipopolysaccharide (LPS), or IFN alone, to induce Mø mediated cytotoxicity towards tumor cells by as much as 40%. GSI-B4 also caused alterations in the pattern of biosynthetically 35S-methionine labeled secreted proteins as early as 2 hours after contact with TG-Møs. Out of 35 discernible proteins on fluorograms of SDS-PAGE separated proteins, 5 were down-regulated and 9 were enhanced. It is suggested that the two novel Mø membrane proteins may play a role in regulating the response of Mø subpopulations to their humoral and cellular environments.

The lytic granules of natural killer cells are dual-function organelles combining secretory and pre-lysosomal compartments

Cytolytic lymphocytes contain specialized lytic granules whose secretion during cell-mediated cytolysis results in target cell death. Using serial section EM of RNK-16, a natural killer cell line, we show that there are structurally distinct types of granules. Each type is composed of varying proportions of a dense core domain and a multivesicular cortical domain. The dense core domains contain secretory proteins thought to play a role in cytolysis, including cytolysin and chondroitin sulfate proteoglycan. In contrast, the multivesicular domains contain lysosomal proteins, including acid phosphatase, alpha-glucosidase, cathepsin D, and LGP-120. In addition to their protein content, the lytic granules have other properties in common with lysosomes. The multivesicular regions of the granules have an acidic pH, comparable to that of endosomes and lysosomes. The granules take up exogenous cationized ferritin with lysosome-like kinetics, and this uptake is blocked by weak bases and low temperature. The multivesicular domains of the granules are rich in the 270-kD mannose-6-phosphate receptor, a marker which is absent from mature lysosomes but present in earlier endocytic compartments. Thus, the natural killer granules represent an unusual dual-function organelle, where a regulated secretory compartment, the dense core, is contained within a pre-lysosomal compartment, the multivesicular domain.

The activation of resting lymphocytes is accompanied by the biogenesis of lysosomal organelles

The degradative activity of lymphocytes plays by important role in a number of essential immune functions. In the present study we have examined how the activation of resting lymphocytes, by the mitogen concanavalin A (Con A), affects three major components of the lysosomal compartment: the lysosomal enzyme beta-glucuronidase (Gus); an integral lysosomal membrane protein (LAMP-1); and the mannose 6-phosphate receptor (MPR) which directs lymphocyte enzyme transport. Resting T cells were found to contain only very low levels of these proteins, but they were actively synthesized by, and far more abundant in, stimulated lymphoblasts. Although the lysosomal antigens did not have a distinct cytoplasmic localization in the resting lymphocytes, in the activated T lymphoblasts they were present in several highly developed intracellular structures, including the rough endoplasmic reticulum and the Golgi complex. Furthermore, in these latter cells Gus was also found to be accumulated within the lumen of large vesicles which we characterized as lysosomes by the presence of LAMP-1 at the periphery and by the absence of MPR. Subcellular fractionation confirmed that these organelles were present in the activated lymphocytes only, and not in the resting T cells. Our results demonstrate that lymphocyte activation is accompanied by the synthesis of the enzymic and structural components of the lysosomal compartment which are sorted and assembled into distinct organelles in the activated cell.

Two proteins targeted to the same lytic granule compartment undergo very different posttranslational processing

The granules of natural killer (NK) cells contain cytolysin and serine proteases, proteins that are expressed specifically in cytolytic cells and are released in response to target binding. We have used immunofluorescence and immunoelectron microscopy to localize these proteins with respect to the various morphological compartments of granules in a rat NK cell line. Both cytolysin and the proteases are limited to the core regions of the dense core granules. While these proteins are targeted to the same compartment, they differ markedly in their posttranslational processing. Cytolysin bears N-linked oligosaccharides that are converted to the complex type, while the major trypsin-like protease, granzyme A, bears only high-mannose-type oligosaccharides. The glycans of granzyme A, but not those of cytolysin, are modified with phosphomannose moieties. These results suggest that one possible mechanism for packaging proteins into NK granules is the mannose 6-phosphate-dependent lysosomal targeting system. However, the absence of the mannose 6-phosphate modification from cytolysin suggests the existence of yet another targeting system.

Arylsulphatase in echinoderm immunocompetent cells

Two peaks of arylsulphatase activity were detected biochemically in coelomocyte lysate preparations of seven different Echinodermata species. Both peaks were inactivated by sulphite and sulphate ions, indicating that Type II arylsulphatase is present in the coelomocytes of the species tested. Arylsulphatase was localized histochemically in the granules of spherula cells, suggesting that in echinoderms a common cell type with granulocyte-like functions is present. The enzyme was also localized in the amoebocytes of echinoid species.

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.

Arylsulfatase in coelomocytes of Holothuria polii

Holothuria polii coelomocytes possess arylsulfatase enzymes. Two pH optima were found for arylsulfatase activity in cell lysate preparations, one at pH 5.0 and the other at pH 5.8. Both increased after injection of zymosan particles or formalinized sheep red blood cells (fSR-BC), indicating an active role of the enzymes during phagocytosis of particulate substances. Under a light microscope, the acid hydrolase arylsulfatase were localized in the granules of spherula cells, and therefore considered lysosomal in nature.

Adhesion of T and B lymphocytes to fibroblasts in tissue culture

We have examined the direct interaction of lymphocytes with human fibroblasts in vitro. The results of our study, using radiolabelled lymphocytes, show that activated T cells rapidly adhered to the fibroblasts when the two types of cell were cultured together at 37 degrees, and that the residency time of lymphocyte-fibroblast contact was approximately 30 min. Lymphoblast adhesion did not require the presence of divalent cations, but it was temperature-dependent. Although the binding of the lymphocytes was not prevented by the presence of monosaccharides or by treatment with exoglycosidases, it was highly sensitive to low concentrations of trypsin. Attachment was also inhibited partially in the presence of the sulphated fucose polysaccharide, fucoidan. These results suggest that at least two distinct receptors are involved in lymphocyte adhesion to fibroblasts. The binding of B lymphoblasts to fibroblasts was much greater than that of the activated T cells. Resting, non-stimulated, B and T lymphocytes both bound only very poorly, showing that only mature lymphocytes express high levels of functionally effective adhesion proteins. Moreover, the results of competition experiments suggest that different cell surface components mediate the interaction of T and B cells with fibroblasts.

Ultrastructural studies of a lysosomal enzyme during lymphocyte activation

A post-embedding immunogold technique has been used for the ultrastructural localization of a lysosomal enzyme, beta-glucuronidase, in resting and activated T- and B-lymphocytes. The results presented here show that mitogen-induced stimulation of T- and B-cells was associated with an increase in the amount of enzyme in the Golgi complex and rough endoplasmic reticulum, organelles which were rarely present in the resting lymphocytes.

Interferon-alpha induction of lymphocytes containing parallel tubular structures

The induction by IFN-alpha in peripheral blood lymphocytes of parallel tubular structures (PTS) and/or electron-dense granules occurring in a minority of peripheral blood lymphocytes was examined. IFN reportedly augments natural killer (NK) cell activity of large granular lymphocytes (LGL); these cells contain PTS and/or electron-dense granules. Normal peripheral blood mononuclear cells were incubated with IFN-alpha and surface antigen expression was measured by means of indirect immunofluorescence and, at the ultrastructural level, using gold labelled monoclonal antibodies. Surface antigen reactivity with the monoclonal antibodies OKT 3, 4, 8 and Anti-Leu-7 (HNK-1) showed no difference between the IFN-alpha incubation and non-IFN-alpha groups. However, electron microscope investigation revealed significant absolute increases in the percentage of OKT 8+ and Anti-Leu-7+ cells which were PTS-positive after IFN-alpha treatment compared with the control groups. The cytotoxicity assay using the K562 cell line showed enhanced lytic activity. Our results suggest that cells coexpressing the OKT 8 and Leu-7 antigens may be responsible for a minor proportion of the increase in PTS but that IFN-alpha mainly induces PTS and/or associated structures in cells which express the OKT 8+ antigen. These PTS+/OKT 8+ cells may contribute to enhanced cell cytotoxicity.

Cytochemical localization of arylsulfatase in guinea-pig Kurloff cells

Kurloff cells are mononuclear cells characterized by a large metachromatic and PAS-positive inclusion called the Kurloff body. Bone-marrow and spleen Kurloff cells were incubated with p-nitrocatechol sulfate as substrate and barium chloride as capturing agent for the ultracytochemical detection of the lysosomal marker enzyme, arylsulfatase. Enzymatic reaction product was consistently found as a single spot-like deposit confined to the rim of the Kurloff body. These results, and the previously described presence of other acid hydrolases and sulfated glycosamino++glycans, emphasize the similarities between the Kurloff body and lysosomes. Reaction product could also be found occasionally in segments of the rough endoplasmic reticulum but it was absent from the Golgi apparatus. This arylsulfatase activity could be related to the natural killer activity of Kurloff cells.

Ultrastructural localization of a lysosomal enzyme in resin-embedded lymphocytes

The intracellular distribution of lysosomal enzymes in lymphocytes has previously been only poorly defined, mainly by cytochemical procedures of low resolution. In the present study we have used a post-embedding immunogold technique to identify the precise ultrastructural localization of a lysosomal enzyme, beta-glucuronidase, in activated lymphocytes embedded in Lowicryl K4M resin. We show that this enzyme is present in the rough endoplasmic reticulum, in the Golgi complex, and in vesicular organelles which probably include lysosomes.

The T cell-specific serine proteinase TSP-1 is associated with cytoplasmic granules of cytolytic T lymphocytes

This study describes the localization of the previously purified T cell-specific serine proteinase, termed TSP-1 (M. M. Simon et al., EMBO J. 1986. 5: 3267), within cytoplasmic granules of cytolytic T cell lines (CTLL). Subcellular fractionation of disintegrated CTLL (ruptured by nitrogen cavitation) was accomplished by Percoll density gradient centrifugation of cell lysates (postnuclear supernatant). Individual fractions were tested for proteinase activity on chromogenic peptide substrates and for the presence of TSP-1 by Western blot analysis. In addition, each fraction was assayed for cytolytic activity against sheep red blood cells (SRBC), for protein and for additional marker enzymes to assess the enrichment for cellular organells. All serine enzyme-type molecules including TSP-1 expressed by CTLL were identified by labeling cell lysates or gradient fractions with the serine proteinase-specific affinity ligand tritiated diisopropyl fluorophosphate [( 3H]DFP) in the presence or in the absence of class-specific or enzyme-specific proteinase inhibitors and subsequent sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The data demonstrate that the Percoll gradient fraction, which was shown by morphological examination in the electron microscope to be highly enriched for cytoplasmic granules, also contained greater than 80% of proteinase activity in addition to the granule-associated structures cytolysin and arylsulfatase. The identity of the granule-associated proteinase in two independent cell lines, CTLL HY3-Ag3 and CTLL 1.D.9, with the serine proteinase TSP-1 is indicated by its specificity for the chromogenic substrate H-D-Pro-Phe-Arg-p-nitroanilide, its sensitivity to class-specific as well as TSP-1-specific enzyme inhibitors and by its reactivity with a polyvalent TSP-1-specific rabbit antiserum. Both CTLL contain a [3H]DFP-labeled protein that migrates with a molecular mass of 60 kDa under nonreducing conditions and with 30 kDa under reducing conditions and which can be inactivated by the TSP-1-specific inhibitor H-D-Pro-Phe-Arg-chloromethylketone. CTLL HY3-Ag3 (a long-term culture CTLL with natural killer-like activity) but not CTLL 1.D.9 (an antigen-specific short-term cultured CTLL) express in addition a further [3H]DFP-binding protein which migrates with 27 kDa under nonreducing or reducing conditions. No substrate specificity was found for this molecule. The possible function of the granule-associated serine proteinase TSP-1 is discussed.

Immunoultrastructural studies of human NK cells: I. Ultracytochemistry and comparison with T cell subsets

Human NK activity is known to be associated with a population of large granular lymphocytes (LGL) exhibiting several immunophenotypic surface markers including Leu-11a (NKP-15), Leu-7 (HNK-1), Leu-3a (T4), and Leu-2a (T8). Based upon correlation with cytolytic activity, Leu-11a is now considered the most specific antigenic marker for human NK cells. Present investigation compared the ultrastructure of cells expressing Leu-11a, Leu-7, Leu-3a, and Leu-2a, both in human peripheral blood lymphocytes (PBL) and the purified LGL fraction. Subcellular cytochemical reactions were investigated in Leu-7+ or Leu-11a+ PBL or LGL and in cells conjugated with K562 targets (indicating NK cytolytic potential). The surface markers, localized with monoclonal antibodies, were detected by immunoelectron microscopy by using direct or indirect avidin-biotin-peroxidase (ABC) or colloidal gold methods. A peroxidase-colloidal gold double-labeling system was used to identify subsets of Leu-7+ or Leu-11a+ cells. Previously described ultrastructural features of LGL including a villous surface, reniform nuclei, low nuclear/cytoplasm ratios, and abundant cytoplasm with vesicles, vacuoles, electron-dense granules, parallel tubular arrays (PTA), or paracrystalline inclusions were associated with Leu-7+, Leu-11a+, Leu-7+/Leu-11a+, Leu-7+/Leu-11a-, and Leu-7-/Leu-11a+ PBL or LGL. Results showed that the Leu-7+/Leu-11a+ cells were the most abundant NK cells in PBL. Lymphocyte subsets with Leu-3a or Leu-2a surface marker showed some ultrastructural features including PTA similar to Leu-7+ cells and Leu-11a+ cells, and their subsets. These T-cells appeared ultrastructurally more similar to the Leu-7+/Leu-11a- subset. Cytochemical studies showed that electron-dense cytoplasmic granules and PTA typical of the Leu-11a+ cells and Leu-7+ cells contained glycoprotein, acid phosphatase, and arylsulfatase. Large cytoplasmic vacuoles were heterogeneous and typically contained electron-dense material with DAB reactivity, membranous material, PTA, and/or paracrystalline inclusions. Glycoprotein, acid phosphatase, and arylsulfatase, and peroxidase reactive material were also found in these vacuoles. These features suggested that the vacuoles could be secondary lysosomes. The coexistence of intact PTA or degenerating PTA in the same vacuoles with paracrystalline inclusions suggested that the latter are possibly derived from PTA.

Immunoultrastructural studies of human NK cells: II. Effector-target cell binding and phagocytosis

The binding of NK cells to a target cell appears to be a necessary step for NK cell-mediated cytolysis. In this report, we demonstrated effector-target binding by immunoelectron microscopy by using monoclonal antibodies against NK cells (Leu-7, Leu-11a) and T-cell subsets (Leu-2a/T8, Leu-3a/T4). The surfaces of NK and K562 cells were characterized by antitransferrin receptor antibody and various lectins. In addition, the controversial phagocytic activity of NK cells was studied by incubation of peripheral blood mononuclear cells with opsonized Staphylococcus aureus and labeling with anti-Leu-7 or anti-Leu-11a antibody. Results showed that only Leu-11a+ cells displayed a broad cell-to-cell contact with the target by a shallow intercellular interdigitation of cytoplasmic projections, while Leu-7+, Leu-2a+, or Leu3a+ cells showed only a partial contact with target without interdigitation. The Leu-11a+ cells were frequently observed in small clusters and in close association with monocytes. Cluster formation and association with monocytes were not observed in other NK and T-cell immunophenotypes. In Leu-11a+ cells conjugated with target cells, membrane-bound granules, small vesicles, parallel tubular arrays, Golgi apparatus, endoplasmic reticulum, and small vacuoles were evident and concentrated toward the target. The surface of NK cells was intensely stained for glycoprotein by chromic acid-phosphotungstic acid, whereas target cells were not stained. Transferrin receptors were stained only on the surface of target cells. Only the lectins RCA and UEA labeled the surfaces of both NK and target cells. Phagocytic vacuoles containing cell debris or fragments and ingested bacteria were found in the cytoplasm of Leu-11a+ cells but not in Leu-7+ cells. NK cells were also found within the cytoplasm of K562 target cells. All these findings suggest that Leu-11a+ cells are the true functional NK cells involved in NK cell-mediated cytolysis, phagocytosis, and emperipolesis. Therefore, the NK cell is probably "a phagocyte in lymphocyte's clothing." The presence of peroxidase in the small vesicles of NK cells and endocytotic vesicles of target cells at the effector-target contact area indicates that cytolytic enzymes or factors derived from NK cells may be transported into the target by endocytosis.

Lymphocyte emperipolesis into autologous monocytes in leukocyte cultures exposed to mitogenic lectins

Lymphocyte-monocyte synergistic interaction in cooperative response to mitogens and antigens is well established. This paper describes a less known--antagonistic (effector-target)--lymphocyte-monocyte interaction that came into existence in a leukocyte culture after the commencement of cellular response to concanavalin A, phytohemagglutinin and Wistaria floribunda mitogen. An invasion of lymphocytes into monocytes and monocyte polykaryons has been found 24-48 h after exposure to mitogens. The invasion is not followed by lysosome fusion with lymphocyte-bearing vacuoles, but is associated with a sequential destruction of the vacuole wall, and eventual disintegration of some affected cells. The expression of pan-T-cell surface antigens, staining patterns for nonspecific esterase and acid phosphatase as well as ultrastructural features show that the lymphocytes entering into and those located within monocytes and polykaryons represent activated T-cells. The presence of developed Golgi complexes associated with coated and smooth vesicles, and lysosomal bodies with microvesicles, tubular arrays or dense cores suggest that these T-cells belong to subpopulations which possess cytolytic activities. The lymphocyte invasion is considered cytolytic emperipolesis directed towards some autologous cells of the mononuclear phagocyte series. Its extent depends upon the mitogen concentration, and density of cell population in the culture. It also shows individual variability. The relationship of cytolytic emperipolesis to phagocytosis, and its possible significance as a mechanism of cell-mediated elimination of undesirable cells is discussed.

Cell-mediated cytotoxicity by natural killer and killer cells, lipid peroxidation and glutathione

In the course of spontaneous cell-mediated cytotoxicity (SCMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) with human peripheral lymphocytes as effector cells, no lipid peroxidation occurred as measured by the production of ethane and thiobarbituric acid-reactive material. Furthermore, impairment of major cellular defense systems of target cells (K562 cells for SCMC, Chang liver cells for ADCC), by decreasing their glutathione content, had no effect on either lipid peroxidation or the cytotoxic response. These findings indicate that peroxidative damage is not a mechanism of NK and K cell-mediated cytotoxicity.

Susceptibility to NK cell lysis is abolished in tumor cells by a factor which restores their contact inhibited growth

It is well recognized that physical contact between natural killer (NK) cells and tumor targets is necessary for cell lysis. Therefore, any modulation of the tumor cell surface that alters intercellular contact could affect NK cell cytotoxicity. To examine this hypothesis, a contact inhibitory factor (CIF), which had been shown to restore contact inhibition of growth to several malignant cell lines was tested for its ability to render such cells immune to recognition by NK cells. When three NK-sensitive melanoma and two NK-sensitive colon carcinoma targets were cultured with CIF, they did not only change morphologically, but also showed a 70% to 95% reduction in their sensitivity to lysis by NK cells. In addition, K562 cells, which grow in suspension and do not permit a morphologic evaluation of the CIF effect, also became resistant to lysis by NK cells after culture with CIF. CIF did not reduce the viability nor the cytotoxicity of NK cells. CIF did not contain interferon nor did the CIF-treated targets induce the production of interferon during the cytotoxicity assay. It is concluded that restoration of contact inhibition of growth and resistance to NK cell lysis are cell surface phenomena that may run in parallel.

Expression of a particular beta-N-acetylglucosaminidase isoenzyme in human haematopoietic leukemic cell-lines

N-acetyl-beta-D-glucosaminidase (NAG) activity and isoenzyme profiles were studied in myeloid, histiocytic, B-lymphoid, T-lymphoid and lymphoblastoid continuous cell lines in order to determine if N-acetyl-beta-D-glucosaminidase isoenzyme expression may help to distinguish among various types of leukemic proliferation. Total NAG activity in myeloid, histiocytic, erythroleukemic cell lines were higher than Burkitt's lymphoma derived cell lines (B-lymphoid), T- or lymphoblastoid cell lines. On chromatofocusing by PBE 94 coupled with an automated enzyme assay an intermediate (I) beta-N-acetyl-glucosaminidase form, eluting between forms B and A, was found in all leukemic and in Epstein-Barr virus infected lymphoblastoid cell lines analysed. The different profiles recorded, the expression of the I form and the different I/B ratios may be useful as markers of tumour proliferation.

Proteoglycans in cell-mediated cytotoxicity. Identification, localization, and exocytosis of a chondroitin sulfate proteoglycan from human cloned natural killer cells during target cell lysis

A clone of natural killer (NK) cells (JTB18) was found to be ultrastructurally similar to peripheral blood large granular lymphocytes (LGL). These cells incorporated [35S]sulfate into cell-associated proteoglycan molecules, which were then isolated by CsCl density gradient centrifugation. As assessed by gel filtration chromatography, the native 35S-labeled proteoglycan and its beta-eliminated 35S-labeled glycosaminoglycans were of Mr approximately 200,000 and 50,000, respectively. The 35S-labeled proteoglycans were resistant to proteolysis, since their Mr were apparently not altered by incubation with either pronase or S. aureus V8 protease. The purified NK cell 35S-labeled proteoglycans were degraded by approximately 90% to 35S-labeled disaccharides with either chondroitinase ABC or AC. High performance liquid chromatographic analysis of the digests revealed these disaccharides to be composed entirely of chondroitin sulfate A (glucuronic acid----N-acetylgalactosamine-4SO4). Whole 35S-labeled cells incubated with chondroitinase ABC failed to release 35S-labeled disaccharides into the supernatant, and x-ray energy-dispersive analysis revealed that sulfur-containing molecules were present in the intracellular granules, thereby localizing the NK cell-associated proteoglycan primarily in the granules of the cell, rather than on the plasma membrane. The 35S-labeled cloned NK cells incubated for 30 min to 4 h with K562 tumor cell targets at a 0.5:1 ratio exocytosed a mean of 49% of the granular 35S-labeled proteoglycans during the first 60 min of the culture. Proteoglycan release was maximal with an effector/target cell ratio of 0.5:1 for JTB18:K562. Significant proteoglycan release from JTB18 NK cells was also obtained with other sensitive target cells such as REX, Molt4, and CEM, but not with cells such as KG1 and Laz156, which have been shown previously to be resistant to killing by this NK cell. Thus, protease-resistant intracellular proteoglycans with chondroitin sulfate A side chains are specifically exocytosed from the granules of human NK effector cells upon contact with sensitive targets, suggesting that these proteoglycans may be involved in the mechanism of cytotoxicity.

Appearance of cytolytic granules upon induction of cytolytic activity in CTL-hybrids

Examining a CTL-line (B6.1) with specific cytolytic activity, we have confirmed the ability of CTL-lines to produce poly C9-like, tubular complexes of two sizes (polyperforin 1 and 2). Isolated cytoplasmic granules from this cell line can induce hemolysis and contain the lysosomal marker arylsulfatase. Electron microscopial studies show that granules contain precursor molecules which are assembled into polyperforin upon addition of Ca2+. Antibodies raised against granules predominantly react with a 27-kd protein. We compared the B6.1 cell with a hybrid, PC60, derived from a cross between B6.1 and a non-cytolytic rat-thymoma. This hybrid line exhibits inducible CTL-activity. In PC60 with induced cytolytic activity, polyperforins 1 and 2, cytolytic granules and granule-associated proteins are detected. Non-cytolytic PC60 cells lack cytolytic granules and polyperforin 1, but contain polyperforin 2. These results suggest that cytolytic granules appear in parallel with the expression of cytotoxicity during T-lymphocyte differentiation.

Cytolytic activity of purified cytoplasmic granules from cytotoxic rat large granular lymphocyte tumors

Purified cytoplasmic granules from cytotoxic rat large granular lymphocytes (LGL) tumors were cytolytic to erythrocytes, splenocytes, and a number of different lymphoid tumor cells. Granule concentrations of approximately 1 microgram/ml granule protein were adequate to lyse 100% of the erythrocytes, while the nucleated cells required up to 100 micrograms/ml granule protein to achieve complete lysis. Cytoplasmic granules purified from noncytotoxic lymphoid cells did not contain detectable cytolytic activity; purified granules from rat mast cells and rat liver lysosomes likewise failed to display cytolytic activity. However, granules prepared from normal rat peripheral blood LGL were cytolytic. Granule-mediated lysis of erythrocytes and nucleated cells was complete within 3 min at room temperature. The lytic activity required calcium at concentrations of 10(-4)-10(-2) M; magnesium or barium failed to replace calcium, while strontium could replace calcium at 10(-3)-10(-2) M when nucleated cells were the target. Exposure of LGL tumor granules to calcium before the addition of target cells resulted in an inactivation of granule cytolytic activity over the course of 20 min at room temperature. Granule cytolytic activity was heat and Pronase sensitive, and could be solubilized by 2 M salt. Examination of granules exposed to calcium in the electron microscope using negative staining showed that calcium treatment of granules results in the formation of ring-shaped structures previously described to be associated with LGL-mediated cytotoxicity. These results provide support for the hypothesis that the cytotoxic processes mediated by LGL are a secretory event characterized by the release of cytolytic material from the cytoplasmic granules after triggering by a surface receptor. The results further suggest that the ring structures visible in the electron microscope are associated with the lytic event.

Neoplastic cells as targets of spontaneously cytotoxic lymphocytes: studies with natural killer-like cell lines

Native natural killer (NK) cells comprise a heterogeneous family of lymphocytes distributed among several organs, which display spontaneous cytotoxic reactions directed against a broad range of tumor targets. In these studies, murine cell lines have been established in vitro following the selective expansion of bone marrow- and spleen-derived killer progenitors in culture medium supplemented with interleukin-2. Several clones of independent origin have been characterized in order to determine the extent of their phenotypic and functional diversity. With few exceptions most of them were found to be highly effective in lysing a variety of tumor cell lines, to share common cell surface alloantigens, lectin-binding receptors, and cytochemical markers. The presence of prominent azurophilic cytoplasmic granules is the most characteristic ultrastructural feature of these cells. In attempting to elucidate the nature of membrane components specifically recognized by NK cells we compared several isogenic tumor cell variants selected on the basis of their differential NK susceptibility, immunogenicity, metastatic potential or resistance to cytotoxic plant lectins. Sialylated glycoconjugates exposed on the external face of the tumor cell membrane appear to be essential determinants in the interaction between NK cells and their targets. Permanent cell lines retaining most of the functional attributes of endogenous NK cells may prove instrumental in understanding their role during tumor progression.