In vitro propagation of cultured human natural killer cells expressing the HNK-1 differentiation antigen and spontaneous cytotoxic function

Analysis of Minor Acidic N-Glycans in Human Serum

Prior investigations by our research group focused on the method development for the simultaneous analysis of sulfated and phosphorylated glycans. Herein, the developed method was applied to analyze minor acidic N-glycans including sulfated and phosphorylated N-glycans in human serum. First, 2-aminobenzoic acid-labeled minor acidic N-glycans were enriched from the serum using a serotonin-immobilized column and were then separated into groups using hydrophilic interaction liquid chromatography, and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Phosphorylated hybrid-type and sulfated bi-antennary N-glycans were detected in the serum. In addition, we observed that multiple types of glucuronidated N-glycans were present. These results indicate that the developed method is applicable to the analysis of glucuronidated as well as sulfated and phosphorylated N-glycans. It was also applied to the sera obtained from 17 healthy subjects and 15 pancreatic cancer patients, and the profiles of sulfated, phosphorylated, and glucuronidated N-glycans were compared. The expressed amount of glucuronidated N-glycans was significantly decreased in some pancreatic cancer patients. Numerous examples of the N-glycan analysis in human serum were reported, but phosphorylated and glucuronidated glycans were not investigated. The methods described herein allow the analysis of minor acidic glycans that are typically difficult to detect.

Proliferation of IL-2 activated lymphocytes preferably occurs in aggregates by cells expressing the CD57 antigen

Aggregates of lymphocytes were investigated in long-term cultures of IL-2 stimulated peripheral blood mononuclear cells. Cells in clusters formed broad contact areas where coated pits and vesicles were often detectable. Proliferating cells were preferably found in aggregates indicating that the cell clusters represent proliferation centres in which cell division may be promoted by accessory signal transduction mediated by the close cell-to-cell contact. In bulk cultures CD57+ cells yielded increased proliferation capacity compared to CD57- cells. In addition, CD57+ cells were preferably localized in aggregates where they occupied the same position at the periphery of the clusters than the proliferating cells, suggesting that both cell types may be identical. It is discussed that the CD57 antigen represents a differentiation marker which is upregulated when CD57- cells start to proliferate assisted in cell aggregates.

An appropriate in vitro culture condition for the induction of human TCR gamma delta + cells by heat-killed bacteria

TCR gamma delta + cells proliferated when MNC were stimulated with various heat-killed bacteria. We investigated here the culture conditions for their maximum proliferation. MNC were cultured for 6 days with Streptococcus pyogenes, and for 3 days with T cell mitogens, PHA and anti-CD3 mAb, in medium supplemented with various concentrations (0.05-50%) of human sera. TCR gamma delta + and TCR gamma delta- CD2+3- double negative cells induced by Str. pyogenes required high concentrations of sera (greater than 6%) for their proliferation. Moreover, increased sera (up to 50%) greatly augmented their proliferation. On the other hand, TCR alpha beta + cell proliferation induced by T cell mitogens was supported by a small concentration (even 0.1%) of the sera, and the addition of high concentrations of sera (greater than 6%) somewhat suppressed responses. Similar serum requirement patterns were evident for the induction of cytotoxic cells. These results clearly demonstrated the existence of an appropriate culture condition for the proliferation of TCR gamma delta + cells induced in vitro.

Ultrastructure of cell mediated cytotoxicity

Contact dependent cell mediated cytotoxicity has been found to be executed by lymphocytes, macrophages, and even granulocytes. Cytotoxic effector cells of the lymphatic lineage are divided into cytotoxic T lymphocytes (CTL), mediating MHC related cytotoxicity, and in effectors mediating non-MHC restricted cytotoxicity such as natural killer (NK) cells, T lymphocytes displaying NK-like activity and lymphokine activated killer (LAK) cells. In morphologic studies these cells are hardly to be distinguished: they all show features of large granular lymphocytes (LGLs), which are characterized by a low nuclear to cytoplasmic ratio and azurophilic granules. Ultrastructurally lysosomal granules, showing an electron dense core that is either surrounded by numerous small vesicles or by a small electron translucent halo, have been found. Pore-forming proteins such as perforin, as well as serine esterases and proteoglycans have been pointed out in these granules. Specialties are parallel tubular arrays (PTA) in NK cells and nuclear inclusion bodies in LAK cells. Morphologically two types of killing event may be distinguished. In one way membrane lesions develop at the surface of target cells upon binding of effector cells and in advanced stages of cytolysis the target cells are surrounded by a completely disintegrated membrane. The nuclei, however, show only minor changes. In the other way, called apoptosis, the cell membrane of the targets remains intact, but the nucleus and cell organelles very early disintegrate intracellularly. Whether these morphologically different types of cell killing correspond to the functionally different pathways of cell mediated cytotoxicity remains to be resolved.

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.

A comparison of fresh and cultured T lymphocytes from patients with ataxia telangiectasia using T-cell subset markers and chromosome translocations

Ataxia telangiectasia (A-T) is an autosomal recessive disorder in which patients show an unusual predisposition to lymphoid malignancies including T-cell leukaemia. We compare here the surface phenotypes of fresh and cultured A-T T cells. A total of 17 T-cell cultures from 8 A-T patients are compared with each other and with 5 T-cell cultures from normal individuals. The large, cytogenetically abnormal t(14;14) and t(X;14) clones in 2 of the patients both occurred only in the CD8+ population of T lymphocytes. There was no difference in the rate of growth of A-T T cells in vitro compared with those from normal individuals, although many of the original characteristics of the T cells were lost, including the cytogenetically abnormal clones seen in fresh A-T lymphocytes.

Phenotypic characterization of murine lymphokine-activated killer cells

Short-term culture of murine lymphocytes in interleukin 2 (IL-2), in the absence of any priming antigen, has been shown to result in the differentiation of an activated killer cell population capable of potent cytotoxic activity against tumor cells. The progenitor and lineage of these lymphokine activated killer cells (LAK) remains controversial. The present study was initiated to combine both complement-mediated depletion and flow cytometry to examine the cell surface membrane markers on murine LAK precursors and effectors. Selective depletion of antigen-positive cells from the precursor or effector population followed by functional assays demonstrates that the LAK effector is derived from a non-thymus-processed cell (Thy-1 negative). Paradoxically, the effector acquires Thy-1 expression in parallel to the IL-2 induced acquisition of killer cell effector function. These studies clearly show that both precursor and effector cells express the "NK-associated" Qa 5 and asialo GM-1 surface antigens. Mature effectors, but not the precursors, exhibit both Lyt-2 and the "NK-associated" NK-1.1 cell surface marker. Our flow cytometric analyses of murine spleen cells activated in rIL-2 have identified a distinct large, granular cell population which contains the LAK effector. This population, which can be readily discerned using light scattering properties with a flow cytometer, demonstrates both quantitative and qualitative changes in cell surface antigen expression.

Natural killer cell activity following T-cell depleted allogeneic bone marrow transplantation

We have examined the recovery of natural killer (NK) cell function in seven recipients of MHC matched T cell depleted bone marrow allografts. NK cell activity against the erythroblastoid line K562 recovers 2-3 weeks after transplantation. Recipients also show a high level of killing of the T cell target HSB2 and of EBV transformed lymphoblastoid cell lines (B-LCL). This activity peaks at 4-6 weeks and declines towards normal by 12-14 weeks after transplantation. Although killing of HSB2 and B-LCL is usually the property of activated NK cells, few of these patients had any obvious 'trigger' of such activation: none had CMV infection, there were no episodes of graft rejection, and only two patients had mild and transient grade I graft versus host disease (GvHD). We conclude that T cell depletion does not affect the reconstitution of NK cell function and that NK cell activation occurs after T depleted bone marrow transplantation even in the absence of clinically detectable GvHD, graft rejection or CMV infection.

Characterization of two morphologically distinct Leu-7+ cell subsets with respect to Leu-15 antigen. Evaluation of Leu-15 determinant distribution on both E rosetting and non-adherent non-E rosetting cell populations

In the present study the fine structures of Leu-7+-Leu-15+ and Leu-7+-Leu-15- cell subpopulations were characterized by using an immunogold-immunoperoxidase double labelling in electron microscopy. The densities of Leu-15 antigenic sites on both E rosetting (Er) and non-adherent/non-E rosetting (non-A/non-Er) Leu-15 positive cell surfaces were also evaluated by using an immunogold analysis in electron microscopy. A majority of Leu-7+ cells co-expressed the Leu-15 antigen and showed an ultrastructural pattern specific for mature natural killer (NK) cells, i.e. abundant cytoplasm with many organelles, numerous electron dense granules, and irregular outline. On the other hand, a minority of Leu-7+ cells did not express the Leu-15 antigen and showed a clearly different ultrastructural feature in comparison to Leu-7+-Leu-15+ cells. Thus, the presence of the Leu-15 antigen on Leu-7+ cell surface corresponds to ultrastructural features specific to differentiated NK cells and may represent an expression of Leu-7+ cell differentiation. An alternative hypothesis may be that Leu-7+-Leu-15+ and Leu-7+-Leu-15- cells represent distinct cell lineages within non-A/non-Er Leu-7+ cells. Finally, the results of the present study provide proof that Leu-15 antigen is more frequently represented on non-A/non-Er Leu-15+ cells than on Er Leu-15+ cells.

Leu-7-positive cells with monocyte phenotype show different ultrastructural features in comparison to Leu-7-positive cells with T-cell phenotype

The ultrastructural features of the Leu-7-positive - Leu-M3-positive cell subpopulation and the Leu-7-positive - Leu-4-positive cell subpopulation were characterized and compared using immunogold-immunoperoxidase double labelling with immunoelectron microscopy. The majority of Leu-7-positive cells coexpressed a monocyte phenotype and showed an ultrastructural pattern specific for functional natural killer (NK) cells, i.e. a low nuclear/cytoplasmic (N/C) ratio, an irregular outline, many cytoplasmic organelles and electron-dense granules. In contrast, only a minority of Leu-7-positive cells coexpressed a T phenotype, and these were characterized by a high N/C ratio, an even surface and the absence of electron-dense granules. Thus, Leu-7-positive - Leu-4-positive cells may by an immature form of NK cells, and Leu-7-positive - Leu-4-positive and Leu-7-positive - Leu-M3-positive cell subpopulations may represent different stages of Leu-7-positive cell differentiation.

Interleukin-2 apparently upregulates its receptor and induces proliferation of various resting mononuclear leukocytes in the absence of antigen

We demonstrate that exposure to highly purified recombinant interleukin 2 (rIL-2) in the absence of known antigenic stimulation induces/increases the expression of two activation-associated proteins, the interleukin 2 receptor (IL-2R) and 4F2 on "resting" peripheral blood mononuclear cells (PBMC); subsequently, these cells enter the S phase of the cell cycle and proliferate. Dual parameter flow cytometry indicates that the phenotype of the cell population(s) which proliferate following this treatment includes HNK+, DR+, and T3+ cells. A twofold expansion in the number of HNK+ and DR+ cells was observed upon culturing resting PBMC in rIL-2 over a 6-day culture period. While the HNK monoclonal antibody is not specific for NK cells, these data do suggest that antigen independent growth of HNK+ cells may represent an additional mechanism by which IL-2 enhances NK effector activity, i.e., by induction of clonal growth of NK cells. In contrast, several concentrations of recombinant Interferon-gamma failed to produce a similar proliferative response.

Human clones with natural killer function can activate B cells and secrete B cell differentiation factors

Large granular lymphocyte clones were prepared from normal human mononuclear cells. Seven clones were studied in detail. All had high cytotoxic activity against the natural killer (NK) cell target K562 and all were T11- and DR-positive but T4- and T8-negative: none released migration inhibitory factor, a characteristic of helper T cell clones. When these NK cell clones were co-cultured with autologous B cells in a 1:1 ratio, 4 of the 7 induced both IgM and IgG synthesis. Ig production could not be further enhanced by the addition of B cell differentiation factors. The cells stimulated included antigen-specific memory B cells, as the Ig induced contained specific antibody to an antigen, tetanus toxoid, to which the B cell donors had recently been immunized. Supernatants from the helper/NK clones contained B cell differentiation factors, and were able to induce IgG synthesis from the lymphoblastoid cell line CESS and from co-cultured T and B cells. However, NK clone supernatants, unlike the clones themselves, were not effective at inducing Ig synthesis from purified B cells. Instead it appears that NK clones first activate B cells and thus render them responsive to the factors that the clones secrete.

A clonal analysis of human peripheral blood lymphocytes displaying natural killer-like activity

Human Fc gamma receptor-bearing lymphocytes and T cells, prepared by sorting peripheral blood lymphocytes using the B73.1 monoclonal antibody, have been cloned by limiting dilution. Although quiescent lymphocytes of either cell type were unresponsive to interleukin 2 (IL 2), following induction with phytohemagglutinin and/or the BSM B lymphoblastoid cell line they could be expanded in IL 2 utilizing a mixed irradiated feeder system. Clones originating from B73.1+ lymphocytes displayed a characteristic large granular lymphocyte (LGL) morphology but were otherwise functionally and phenotypically heterogeneous. Of 36 clones analyzed 19 displayed significant natural killer (NK)-like activity, each clone having a target cell repertoire identical to uncloned NK effectors. Furthermore, only a minority of clones (i.e. 5) displayed significant antibody-dependent cellular cytotoxicity, while levels of lectin-induced cellular cytotoxicity were normally commensurate with a clones level of NK-like activity. No correlation was evident between the phenotype of a clone and its cytotoxic activity since of 12 cytotoxic clones phenotyped, 8 expressed the OKT3 antigen but lacked the B73.1 antigen; 2 lacked the OKT3 antigen but expressed the B73.1 antigen and one lacked both OKT3 and B73.1 antigens. In addition the expression of OKT8 and OKT4 antigens was not in any way predictive of the cytotoxic capacity of a given clone. Several clones expressing T cell associated antigens bore a phenotype that distinguished them from T cell clones insofar as T cell subset antigens were expressed in the absence of the OKT3 antigen and vice versa.(ABSTRACT TRUNCATED AT 250 WORDS)

Virus-mediated induction in human lymphocytes of antibody-independent cytotoxicity (VDCC) and enhancement of antibody-dependent cytotoxicity (ADCC) against natural killer-resistant tumor target cells

The effect of Parotis virus on the in vitro cytotoxicity of human lymphocytes against NK-resistant mouse mastocytoma cells was studied. In the 51Cr-release assay, treatment of lymphocytes with virus induced a rapid cytotoxicity in the absence of anti-P815 antibody (virus-dependent cellular cytotoxicity, VDCC) and strongly enhanced antibody-dependent cytotoxicity (ADCC). At the effector cell level, virus treatment was found to increase the frequency of target-binding cells (TBC) as well as the proportion thereof mediating VDCC and/or ADCC, indicating recruitment of active effector cells. The recruited cells were heterogeneous but contained a major fraction bearing the T-cell-associated antigen T3. Virus was found to decrease rather than to increase the recycling capacity of the cytotoxic lymphocytes, suggesting that VDCC induction and ADCC enhancement were due to a virus-mediated improvement of effector cell-target cell interactions. VDCC and ADCC enhancement may be of protective importance in early phases of virus infection as well as for the production of nonspecific tissue injuries associated with viral disease.

Preservation of the helper and suppressor/cytotoxic T-lymphocyte phenotype in continuous culture

The objective of the present investigation was to culture helper or suppressor/cytotoxic T cell subsets after extensive purification in interleukin 2-containing medium to determine whether phenotype changes for OKT4/91d6- or OKT8/Leu-2a-defined antigens do occur with prolonged culture. Repeated and sequential analysis of such polyclonally activated cultured T cells documented stability of the OKT4/91d6+ and OKT8/Leu-2a+ phenotype. Both populations could be considerably expanded in culture. However, mixing experiments revealed a growth advantage of the OKT8/Leu-2a+ subset. A significant number of cells expressing both phenotypic markers was not detectable. While cultured T cells promoted on interleukin 2 were stable for expression of these functionally important differentiation markers, additional studies on activation antigens revealed high numbers of Tac+ cells at an early time of culture and decreasing numbers during further incubation. The expression of Tac antigen preceded the exponential expansion of the culture. In contrast, the number of cells bearing Ia determinants steadily increased with prolonged culture.

Characterization of human granular lymphocyte subpopulations expressing HNK-1 (Leu-7) and Leu-11 antigens in the blood and lymphoid tissues from fetuses, neonates and adults

Three subpopulations of human granular lymphocytes from blood and lymphoid tissues were characterized using combinations of the monoclonal antibodies (mAb) HNK-1 (Leu-7), Leu-11 and VEP13. Each subpopulation was confirmed to possess natural killer (NK) cell functional capability, but a different level of cytotoxic efficiency (HNK-1+leu-11- less than HNK-1+Leu-11+ less than HNK-1-Leu-11+). In adult from 23 healthy donors, the subpopulations with HNK-1+Leu-11-, HNK-1+Leu-11+ and HNK-1-Leu-11+ phenotypes comprised 4.7 +/- 3.0, 8.0 +/- 6.4 and 3.9 +/- 3.5% of mononuclear cells, respectively. Despite their distinct surface marker phenotypes and NK functional ability, all 3 subpopulations exhibited granular lymphocyte morphology. One of these subpopulations, HNK-1+Leu-11-, also expressed the pan-T cell antigen Leu-4. Different patterns were observed in fetal bone marrow and cord blood, where the vast majority of HNK-1+ cells lacked the Leu-11 antigen (HNK-1+Leu-11+ cells). The HNK-1 antigen was not expressed on granulocytes and their precursors, whereas both Leu-11 and VEP13 antigens were expressed on these myeloid cells from fetal bone marrow and cord blood as well as adult bone marrow and spleen. Cell lines of granular lymphocytes cultured in the presence of interleukin 2 all possessed the HNK-1+Leu-4+ phenotype and NK functional capability but lacked the Leu-11 and VEP13 antigens on their surface after 15 days of culture. Although granular lymphocytes expressing the Fc receptors reacting with the mAb Leu-11 and VEP13, are the most functionally active NK cells, the HNK-1+ subpopulation lacking the Leu-11 and VEP13 antigens appears to be an important population (possibly an immature form of granular lymphocytes) for delineating the cell lineage(s) and differentiation of human granular lymphocytes. Although none of the currently available mAb react both inclusively and exclusively with human granular lymphocytes, the combination usage of these antibodies permits a more precise and comprehensive analysis of these subsets.

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.