Sensitivity of simian virus 40-transformed C57BL/6 mouse embryo fibroblasts to lysis by murine natural killer cells

The susceptibility of mouse cells expressing full-length or truncated transforming protein (T antigen) of simian virus 40 (SV40) to lysis by murine natural killer (NK) cells was assessed. For these studies, C57BL/6 mouse embryo fibroblasts (B6/MEF) were transformed by transfection with SV40 DNA encoding the entire T antigen. The transformed cell lines were tested for susceptibility to lysis by nonimmune CBA splenocytes as a source of NK cells and to lysis by C57BL/6, SV40-specific cytolytic T cells (CTL). It was found that 13 of 15 clonally derived, SV40-transformed H-2b cell lines were susceptible to lysis by NK cells. However, there was some variation in their susceptibility to lysis by NK cells. There was no correlation between susceptibility to lysis by SV40-specific CTL and to lysis by NK cells. Cells transfected with a plasmid which encodes only the N-terminal half of the SV40 T antigen were consistently less susceptible to lysis by NK cells, suggesting that expression of only the N-terminus of the T antigen was insufficient for optimal susceptibility to lysis by NK cells. Primary mouse embryo fibroblasts transformed by human adenovirus type 5 E1 region DNA were also found to be susceptible to NK cell-mediated lysis. Lysis of SV40-transformed cells by nonimmune CBA splenocytes was mediated by NK cells because: lysis was augmented when the effector cells were treated with interferon before assay; and lysis was abrogated when the effector cells were obtained from mice that had been depleted of NK activity by treatment with antiserum against the asialo GM1 surface marker. These results indicate that primary mouse cells which are transformed by SV40 and which express the native T antigen are susceptible to lysis by mouse NK cells. Conversely, cells transformed by a plasmid encoding only the N-terminal half of the T antigen express reduced susceptibility to lysis by NK cells.     

Monoclonal antibody identification of a type II alveolar epithelial cell antigen and expression of the antigen during lung development

A monoclonal antibody identifying an antigen expressed by rat type II alveolar epithelial cells, but not by type I epithelial cells or other mature lung cells, was produced by immunization of mice with cells of the rat L2 cell line. The antigen recognized by the antibody was present on the microvillous luminal surface of type II epithelial cells. In adult rat lung, only type II epithelial cells bound the antibody. During fetal development the antigen was expressed by cuboidal epithelial cells lining the respiratory ducts of the first divisions of the tracheal bud, but not by epithelial cells lining the esophagus or trachea. The antigen continued to be expressed by cuboidal epithelial cells lining the larger respiratory ducts until approximately 19 days gestational age. Thereafter, expression was increasingly limited to selected single cells or clusters of two to four cuboidal cells in the smallest ducts. By the 21st postnatal day, the antigen was expressed only by type II alveolar epithelial cells. Type II alveolar epithelial cells isolated from adult lung and the L2 cell line in culture expressed the antigen on the cell surface. A protein of approximately 146,000 Mr was isolated by immunoadsorption of the antigen from non-ionic detergent extracts of type II cells and L2 cells. Preliminary studies of the binding of the antibody to other rat tissues indicate that the antibody binds to renal proximal tubular epithelial cells of the kidney and the luminal surface of the small bowel epithelial cells.     

Cellular interaction between fixed and living cells. Transfer of radioactive materials from living cells to fixed cells

Transfer of radioactive materials to fixed cells from an overlying layer of living cells has been examined to determine whether fixed cells can act as acceptors of glycosyltransferases of living cells. After the incubation of living cells were removed by EDTA treatment, and the radioactivity associated with the fixed cells was determined. Lipids, proteins and carbohydrates were found to be transfered from the living cells to the fixed cells. The amount of radioactivity transferred to the fixed cells was dependent on the number of both fixed and living cells and increased with the time of incubation. When fixed cells were treated with chloroform-methanol before the addition of living cells, the transfer of both lipids and proteins to the fixed cells decreased drastically, but only a slight decrease incarbohydrate transfer was observed. Most of the radioactive materials transferred from living cells labeled with glucosamine or fucose to chloroform-methanol-treated fixed cells were solubilized by trypsin but not by the detergents tested. Approximately 55% of the materials transferred from the cells labeled with glucosamine could be solubilized by hyaluronidase and chondroitinase, and the rest was solubilized by neuraminidase and a glycosidase mixture. The treatment of chloroform-methanol-extracted fixed cells with trypsin caused a significant decrease in the transfer from cells labeled with glucosamine. When nucleotide sugars were used as the radioactive precursor, no significant amount of radioactivity was transferred to the fixed cells.     

Immunoregulatory function of T cells activated in the autologous mixed lymphocyte reaction

This study was undertaken to define the functional properties of T cells stimulated in the autologous mixed lymphocyte reaction (MLR) by purified B cells or macrophages. In preliminary experiments, it was found that T cells that had been cultured with autologous non-T cells inhibited pokeweed mitogen- (PWM) stimulated immunoglobulin synthesis by autologous B cells. In addition, the T cell-mediated suppression was eliminated by x-irradiation and hydrocortisone treatment, was mediated by a mechanism that occurred early in the PWM-stimulated cultures, and did not involve killing of mature immunoglobulin-secreting cells. T cells were then cultured with either autologous B cells or macrophages in order to determine whether such autoreactive T cells had a similar capacity to regulate PWM-induced immunoglobulin synthesis. Although T cell populations stimulated either by B cells or by macrophages suppressed proliferative responses and immunoglobulin synthesis, both these populations of autoreactive T cells provided help for immunoglobulin synthesis that was not significantly different from that provided by fresh T cells. These results suggest that the predominant functional consequence of activation of T cells in the autologous MLR is the generation of suppressor T cells capable of inhibiting immunoglobulin synthesis. Thus, the autologous MLR may represent a negative feedback mechanism for the regulation of the immune response.     

Phosphatidylserine-dependent adhesion of T cells to endothelial cells

Phosphatidylserine (PS) was exposed at the surface of human umbilical vein endothelial cells (HUVECs) and cultured cell lines by agonists that increase cytosolic Ca(2+), and factors governing the adhesion of T cells to the treated cells were investigated. Thrombin, ionophore A23187 and the Ca(2+)-ATPase inhibitor 2, 5-di-tert-butyl-1,4-benzohydroquinone each induced a PS-dependent adhesion of Jurkat T cells. A23187, which was the most effective agonist in releasing PS-bearing microvesicles, was the least effective in inducing the PS-dependent adhesion of Jurkat cells. Treatment of ECV304 and EA.hy926 cells with EGTA, followed by a return to normal medium, resulted in an influx of Ca(2+) and an increase in adhering Jurkat cells. Oxidised low-density lipoprotein induced a procoagulant response in cultured ECV304 cells and increased the number of adhering Jurkat cells, but adhesion was not inhibited by pretreating ECV304 cells with annexin V. PS was not significantly exposed on untreated Jurkat cells, as determined by flow cytometry with annexin V-FITC. However, after adhesion to thrombin-treated ECV304 cells for 10 min followed by detachment in 1 mM EDTA, there was a marked exposure of PS on the Jurkat cells. Binding of annexin V-FITC to the detached cells was inhibited by pretreating them with unlabelled annexin V. Contact with thrombin-treated ECV304 cells thus induced the exposure of PS on Jurkat cells and, as Jurkat cells were unable to adhere to thrombin-treated ECV304 cells in the presence of EGTA, the adhesion of the two cell types may involve a Ca(2+) bridge between PS on both cell surfaces. The number of T cells from normal, human peripheral blood that adhered to ECV304 cells was not increased by treating the latter with thrombin. However, findings made with several T cell lines were generally, but not completely, consistent with the possibility that adhesion to surface PS on endothelial cells may be a feature of T cells that express both CD4(+) and CD8(+) antigens. Possible implications for PS-dependent adhesion of T cells to endothelial cells in metastasis, and early in atherogenesis, are discussed.     

Modulation of Immune Response by Bacterial Lipopolysaccharide (LPS): Roles of Macrophages and T Cells in In Vitro Adjuvant Effect of LPS on Antibody Response to T Cell-Dependent and T Cell-Independent Antigens

The roles of macrophages and T cells in the adjuvant effect of lipopolysaccharide (LPS) were studied. In vitro anti-trinitrophenyl (anti-TNP) antibody responses to TNP-Ficoll and TNP-keyhole limpet hemocyanine (TNP-KLH) in spleen cells of C57BL/6 mice showed the most enhancement, when LPS was added to cultures at 1 μg/ml 48 hr after culture was started. The responses to these antigens were enhanced markedly by LPS in whole and macrophage-depleted spleen cells. The enhancement was greater in the latter group than in the former. The adjuvant effect among whole, T cell-depleted, macrophage-depleted and both macrophage- and T cell-depleted spleen cells was compared. The response to TNP-Ficoll was enhanced markedly by LPS in all groups. The enhancement was greater in the latter two groups than in the first two groups. The response to TNP-KLH was enhanced by LPS strongly in macrophage-depleted spleen cells, moderately in whole and both macrophage- and T cell-depleted spleen cells, and only slightly in T cell-depleted spleen cells. Enhancement was restored to T cell-depleted spleen cells by adding T cells. The response to TNP-KLH of macrophage-depleted spleen cells of LPS-responsive C3H/HeN mice which was enhanced by LPS was suppressed by adding splenic macrophages of C3H/HeN mice, but not of LPS-nonresponsive C3H/HeJ mice. The response to TNP-KLH of macrophage-depleted spleen cells of C3H/HeJ mice was not enhanced by LPS, irrespective of the addition of macrophages of C3H/HeN mice. The results indicate that B cells are activated directly by LPS, and T cells enhance and macrophages suppress the adjuvant effect of LPS.     

Differential regulation of IFN-gamma, TNF-alpha, and IL-10 production by CD4(+) alphabetaTCR+ T cells and vdelta2(+) gammadelta T cells in response to monocytes infected with Mycobacterium tuberculosis-H37Ra.

Mycobacterium tuberculosis bacilli readily activate CD4(+) and gammadelta T cells. CD4(+) and gammadelta T cells were compared for their ability to regulate IFN-gamma, TNF-alpha, and IL-10 production, cytokines with significant roles in the immune response to M. tuberculosis. PBMC from healthy tuberculin positive donors were stimulated with live M. tuberculosis-H37Ra. CD4(+) and gammadelta T cells were purified by negative selection and tested in response to autologous monocytes infected with M. tuberculosis. Both subsets produced equal amounts of secreted IFN-gamma. However, the precursor frequency of IFN-gamma secreting gammadelta T cells was half that of CD4(+) T cells, indicating that gammadelta T cells were more efficient producers of IFN-gamma than CD4(+) T cells. TNF-alpha production was markedly enhanced by addition of CD4(+) and gammadelta T cells to M. tuberculosis infected monocytes, and TNF-alpha was produced by both T cells and monocytes. No differences in TNF-alpha enhancement were noted between CD4(+) and gammadelta T cells. IL-10 production by M. tuberculosis infected monocytes was not modulated by CD4(+) or gammadelta T cells. Thus CD4(+) and gammadelta T cells had similar roles in differential regulation of IFN-gamma, TNF-alpha, and IL-10 secretion in response to M. tuberculosis infected monocytes. However, the interaction between T cells and infected monocytes differed for each cytokine. IFN-gamma production was dependent on antigen presentation and costimulators provided by monocytes. TNF-alpha levels were increased by addition of TNF-alpha produced by T cells and IL-10 production by monocytes was not modulated by CD4(+) or gammadelta T cells.     

IL-4 production by T cells from naive donors. IL-2 is required for IL-4 production

Utilizing a sensitive and selective assay for IL-4, it was shown that lymph node T cells from naive mice could produce small amounts of this lymphokine in response to anti-CD3 antibodies adsorbed to culture dishes. The capacity of these cells to produce IL-4 in response to plate-bound anti-CD3 was substantially enhanced by the addition of IL-2 to the culture and was strikingly inhibited by monoclonal anti-IL-2 antibody. Thus, IL-2 appears to be essential for IL-4 production by anti-CD3 antibody-stimulated T cells from naive mice. The effect of IL-2 was not mediated either by preferential proliferation or survival of precursors of IL-4 producing cells, indicating that IL-2 regulates T cell production of IL-4. IL-4 producing capacity of T cells from naive mice was found mainly among CD4+ T cells. Large T cells produced much more IL-4, on a per cell basis, than did small T cells. In contrast, small T cells appeared to be equal or superior to large T cells in producing IL-2. The superiority of large T cells in IL-4-producing capacity was not accounted for by a lack of an accessory cell population from the small T cells as addition of large spleen cells depleted of both B and T cells did not enhance IL-4 production by small lymph node T cells. These results suggest that the bulk of IL-4 production by T cell populations, from normal mice, in response to anti-CD3 depends upon cells that are already activated and that IL-2 is required for such production.     

Effect of osmotic shock on tetracycline resistance in Escherichia coli bearing an R-factor

1. Escherichia coli with an R-factor conferring resistance to tetracycline was induced to high-degree resistance by pre-exposure to the antibiotic. The degree of resistance was drastically lowered by subjecting the cells to osmotic shock. 2. Resistance to tetracycline was rapidly restored by incubating the shocked cells in a glucose-salts medium containing shock proteins prepared from tetracycline-sensitive and -resistant cells. Resistance was also restored by incubating the cells in a complex medium without shock protein. 3. The initial recovery of resistance was followed by a secondary fall in resistance when the cells were cultured in complex medium; this secondary fall was largely prevented by the addition of a low concentration (10mug/ml) of tetracycline to cells. The secondary fall was significantly less in shocked E. coli cells harbouring a mutant R-factor in which tetracycline resistance is largely constitutive. 4. Tetracycline resistance was also transiently depressed by treating R-factor-bearing cells with EDTA in tris buffer. 5. The significance of these results in relation to the mechanism of tetracycline resistance in R-factor-bearing cells is discussed.     

The anticancer drug,cisplatin, increases the naturally occurring cell-mediated lysis of tumor cells

Summary It has been proposed that a component of the antitumor potential of the chemotherapeutic agent, cisplatin, resides in the host's ability to respond to cisplatintreated tumor cells. Here we report that tumor cells that are normally resistant to lysis mediated by naturally occurring cytotoxic cells showed an increased sensitivity to lysis mediated by murine spleen cells or human peripheral blood monocytes and lymphocytes when cisplatin was added at the beginning of the lytic assay. This was shown for the lysis of both murine and human tumor cells. The pretreatment of tumor cells, but not effector cells with cisplatin caused an increase in lysis in the presence of murine spleen cells or human peripheral blood leukocytes, indicating that the effect of cisplatin is to reduce resistance to lysis by these effector cells. The lysis of tumor cells by naturally occurring cytotoxic cells was blocked by antibodies specific for tumor necrosis factor. In addition, the ability of cisplatin to increase lysis was seen with cells that are sensitive to natural cytotoxic cells, but not with cells that are sensitive to natural killer cells. These results suggest that the effector cells that mediate the lysis of these tumor cells in the presence of cisplatin are likely to be natural cytotoxic cells. The ability of cisplatin to increase the lysis of tumor cells by naturally occurring cytotoxic cells indicates that these cells may be a host defense mechanism that contributes to the anticancer potential of cisplatin.     

Suppression of interleukin-2 production by human concanavalin A-induced suppressor cells

When PHA-activated normal responder cells (R cells) were cocultured with mononuclear cells (MN cells) which had been preincubated for 48 hr in medium alone (C cells) an enhanced proliferative response was observed. This enhancement was only obtained when the R cells were cultured with allogeneic C cells or when PHA was in the cocultures for the entire culture period. This effect was due to greater production of interleukin 2 (IL-2) by irradiated C cells in the presence of allogeneic or mitogenic stimulation. Con A-treated mononuclear cells (S cells) cultured with PHA-activated allogeneic or autologous responder cells showed reduced [3H]thymidine incorporation and IL-2 production as compared to activated R cells alone. Glutaraldehyde-treated S cells (which retained the ability to absorb IL-2) did not affect the proliferative response or IL-2 production by the R cells, indicating that passive absorption of IL-2 was not entirely responsible for suppression induced by S cells. S cells, pretreated with IL-2, still inhibited R-cell activity. These results show that Con A-treated MN cells suppressed or prevented [3H]thymidine incorporation by actively inhibiting IL-2 production.     

The biosynthesis of extracellular-matrix components by bovine retinal endothelial cells displaying distinctive morphological phenotypes.

Previous studies have indicated that the morphology and behaviour of bovine retinal microvessel endothelial cells are influenced by culture conditions in vitro. Data are presented here concerning the biosynthesis of matrix macromolecules by bovine retinal endothelial cells cultured under conditions in which the cells display either the 'cobblestone' or the 'sprouting' phenotype. Newly synthesized matrix proteins were identified by their characteristic electrophoretic mobilities, immunoprecipitation with specific antibodies, susceptibilities to enzymic digestions and chromatographic behaviour. Type IV procollagen was the major collagenous species synthesized by early-passage cells forming a 'cobblestone' monolayer. In contrast, cells displaying the 'sprouting' morphology switched to the predominant synthesis of interstitial fibrillar collagens (types I and III). Fibronectin was synthesized by retinal endothelial cells under all the experimental conditions studied. A non-collagenous glycoprotein of Mr approx. 47,000 was also a major biosynthetic product of these cells. The synthesis of thrombospondin was very much dependent on the nature of the substratum on which the cells were cultured. This glycoprotein was synthesized in large amounts by 'cobblestone' endothelial cells cultured on gelatin-coated dishes, whereas its synthesis was markedly decreased by culturing the cells on collagen gels, and the protein appeared to be absent when the cells were plated within collagen gels ('sprouting' cells). Late-passage retinal cells synthesized predominantly type I procollagen, variable amounts of type III procollagen and only traces of type IV procollagen, irrespective of whether the cells displayed a 'cobblestone' or 'sprouting' morphology.     

Delivery of cytotoxic drugs from carrier cells to tumour cells by apoptosis

A new drug delivery approach, apoptotic-induced drug delivery (AIDD), is presented that is based on apoptosis as a mechanism to trigger delivery of drugs from carrier cells. It was investigated whether apoptotic drug-loaded carrier cells could deliver drugs to tumour cells by various mechanisms, including drug release through a more permeable apoptotic cell membrane, and by phagocytosis of drug-loaded apoptotic cells by tumour cells. The feasibility of this novel concept was evaluated in an in vitro carrier cell model that consisted of S49 mouse lymphoma cells that apoptose upon exposure to dexamethasone (DX). Membrane permeability was evaluated by measurement of release of a fluorescent dye (calcein-AM, C-AM) from C-AM-loaded S49 cells. Phagocytotsis of fluorescent PKH-26-labeled S49 cells was determined in co-culture studies with rat glioma (RG-2) cells using fluorescence microscopy and flow cytometry. Cytotoxicity of RG-2 cells due to temozolomide (TMZ)-loaded S49 cells was evaluated by a colony formation assay following co-culture of these cells for up to 8h. Calcein release from S49 cells was enhanced by approximately 30% at 48h following treatment with DX compared to control S49 cells. Based on both flow cytometric and microscopic analyses, RG2 phagocytized apoptotic S49 cells to a four- to sevenfold greater extent than control S49 cells at co-incubation times from 4–48h. The TMZ-loaded apoptotic S49 cells caused the largest degree of toxicity, about 50% cell kill, whereas TMZ-loaded control S49 caused 30% cell kill. The preliminary data suggest that AIDD should be further explored. This revised version was published online in June 2006 with corrections to the Cover Date.     

CN(-)-Induced degradation of nuclei in cells of pea leaves

Degradation of nuclei in epidermal and guard cells of pea leaves was induced by NaCN. Guard cells were considerably more resistant to CN- than epidermal cells. CN--induced nucleus degradation in guard cells was accelerated by illumination. The effect of illumination was negligible in epidermal cells that, unlike guard cells, do not contain chloroplasts. These data may indicate a role of chloroplasts in CN--induced cell death. CN--induced nucleus degradation in epidermal cells was retarded by antioxidants (butylated hydroxytoluene and vitamin E). The effect of CN- in guard cells was largely removed by vitamin E. Salicylic acid, an inhibitor of catalase and ascorbate peroxidase, induced 100% degradation of nuclei in epidermal cells but did not significantly affect nuclei in guard cells. CN--induced inhibition of catalase and peroxidase is assumed to lead to generation and accumulation of reactive oxygen species inducing apoptosis. Like mitochondria, which play an important role in animal cell apoptosis, chloroplasts may take part in apoptosis in plant cells.     

Appearanc of cytotoxic cells within the bronchus after local infection with herpes simplex virus.

Cells from rabbit spleens, bronchial washings (BW) and bronchus-associated lymphoid tissues (BALT) were examined for their ability to lyse cells infected with herpes simplex virus (HSV). Specific lysis of HSV-infected cells was mediated by BW cells as early as 4 days after intratracheal infection of the rabbits with the virus whereas lysis by spleen cells and BALT cells was not detected until 7 or more days after infection. Lysis by spleen cells was initially detected 7 days after intraperitoneal injection of the virus but lysis by BW and BALT cells was not observed until 14 days after infection. Although spleen, BW, and BALT cells could lyse antibody-coated target cells, antibodies detectable by antibody-dependent cellular cytotoxicity could not be detected in bronchial washings until 7 or more days after infection. The data suggest that cells capable of direct cytotoxicity of virus-infected cells appear within the bronchus after local infection by the virus.     

Bovine luteal cells stimulate proliferation of major histocompatibility nonrestricted gamma delta T cells

Luteal cells are potent activators of T cell proliferation in vitro. The purpose of this study was to determine which subset of T cells is stimulated by luteal cells and whether luteal cell-induced T cell activation elicits a proinflammatory or anti-inflammatory T cell response. The first objective was to determine if luteal cell-stimulated T cell proliferation was mediated by class I or II major histocompatibility complex (MHC) molecules. T cell proliferation was inhibited by anti-MHC class I but not anti-MHC class II antibodies. The second objective was to determine which T cell subtype proliferates when cultured with luteal cells. The proportions of CD4(+) and CD8(+) cells were unchanged, but the number of gamma delta T cells was increased by coculture with luteal cells. Immunohistochemistry confirmed the presence of gamma delta T cells in midcycle and regressing corpus luteum. The final objective was to characterize T cell cytokine production stimulated by luteal cells. The concentrations of interferon-gamma (IFNG) and interleukin 10 (IL10) were increased in luteal cell-T cell cocultures, whereas IL4 was undetectable, and IL12 was barely detectable in culture medium. It was concluded that coculture of luteal cells and T cells resulted in activation of a somewhat unique T cell subset, gamma delta T cells, as well as production of both pro- and anti-inflammatory cytokines. To our knowledge, this is the first report of gamma delta T cell activation by luteal parenchymal cells of any species, raising the possibility that tissue-resident gamma delta T cells are involved in regulating the balance between tissue homeostasis and luteolysis.     

A suppressor cell which interferes with antiallotype stimulated DNA synthesis of rabbit B cells

Responsiveness of rabbit spleen cells to anti-allotype antibody was measured in terms of increased thymidine incorporation. Incorporation was enhanced after removal of cells which had ingested or had adhered to magnetic particles. B lymphocytes, prepared from spleen cells by the removal of adherent cells and of RTLA bearing T cells, were more responsive to anti-allotype antibody than were the original spleen suspensions. This increase could not be explained by enrichment in B cells. It was concluded that an adherent cell suppressed B cell transformation. The addition of 2-mercaptoethanol to the cell cultures stimulated with mitogen augmented the incorporation of thymidine. Adherent cells interfered with 2-mercaptoethanol potentiation in the response to anti-allotype antibody but not in the response to Con A. Fractionation of spleen cells, over glass bead columns, yielded nonadherent and adherent cell populations. The responsiveness of nonadherent cells to anti-allotype induced thymidine incorporation was two to six times that of unfractionated cells. The responsiveness of nonadherent cells to stimulation by anti-allotype antibody was reduced after addition of adherent cells. Findings were discussed in terms of the inhibitory role played by adherent cells on anti-allotype antibody induced responsiveness of rabbit B cells and of the possible participation of a third cell type which functions as a promotor of mitogenic T cell stimulation.     

Different effects of an oligonucleotide uptake stimulating protein on leukemic cells in their primitive and differentiated state

The single stranded [³H]oligonucleotide uptake by HL-60 human promyelocyte and K562 human erythroleukemia cells was stimulated 20–45-fold by DUSF (DNA uptake stimulating protein), and this effect was drastically reduced (to 1.6–13×) if the cells were induced to differentiate. The oligonucleotide uptake stimulating effect of DUSF was not altered in HL-60 and K562 cells, if the proliferation of the cells was inhibited by hydroxyurea (HU) treatment. The oligonucleotide uptake by separated granulocytes and mononuclear cells from healthy donors was not stimulated by DUSF, while the uptake of oligonucleotides by myeloid and lymphoid leukemic cells was greatly stimulated (10–15×). The uptake of oligonucleotides by differentiated mononuclear cells of healthy donors could not be stimulated by DUSF, but the oligonucleotide uptake was greatly increased (11×) by DUSF if the cells were subjected to blast transformation.     

Renal carcinoma cell lines inhibit natural killer activity via the CD94 receptor molecule

MHC class I molecules protect normal and transformed cells from lysis by natural killer (NK) cells through recognition of receptors expressed on leucocytes. Defects in NK cell activity and lymphokine activated killer (LAK) cell generation have been previously demonstrated in patients with renal cell carcinoma (RCC). However, to date, the importance of NK receptor/MHC class I interactions for immune evasion by RCC cells has not been described. In this study, human RCC cell lines (HTB46, HTB47, ACHN, CRL 1933 and HTB44) were found to be susceptible to lysis by both NK cells and interleukin-15 (IL-15)-derived LAK cells from normal donors in vitro. However, when NK cells were co-cultured with RCC cells their expression of the CD94 NK receptor molecule was significantly increased and their cytolytic activity against RCC targets was reduced. The cytolytic activity of NK cells was restored by the addition of IL-15, which further augmented the expression of CD94 on CD56+ NK cells. Disruption of NK receptor-MHC class I interactions by the addition of blocking antibodies to CD94 had no effect on the lysis of K562 or HTB47 targets by NK cells. However, the sensitivity of HTB46 cells to NK-mediated lysis was increased by blocking the CD94 receptor molecule, but only when the NK cells had not been previously co-cultured with RCC cells. This was independent of the presence of IL-15. These results show that RCC cells can inhibit NK activity via CD94 and suggest that disruption of interactions between receptor and ligand on RCC cells in vivo may augment the immune response against tumours by innate effector cells.