Defective NK cell activity following thermal injury.

Peripheral blood mononuclear lymphocytes (PBL) from thermal injury patients were examined for their ability to mediate natural killer (NK) cell activity against K562 tumour cells and against herpes simplex virus type 1 (HSV-1) infected Raji tumour cells. Using fluorescein isothiocyanate-conjugated monoclonal antibodies, the number of T3, T4, T8, Leu11, and Leu7 positive cells in PBL obtained from patients and normal controls was determined. Thermal injury patients had decreased levels of T3+ cells and a T4:T8 ratio which was significantly lower than that found in normal control individuals. Although patients had normal percentages of Leu7+ and Leu11+ cells, they had depressed NK cell activity against both K562 tumour cells and HSV-1 infected Raji cells. NK cell activity against K562 tumour cells was severely depressed during the first 20 days after injury. This defective NK cell activity did not appear to be due to a defect in PBL binding to the K562 tumour cells. In patients, the level of NK cell activity against HSV-1 infected cells did not correlate with the level of NK cell activity against K562 tumour cells. This finding further supports previous reports showing that NK cells which kill K562 tumour cells are different from the NK cell population which kills HSV-1 infected cells. Pretreatment of PBL obtained from patients with IL-2 or IFN-alpha, in some cases greatly enhanced NK cell killing of K562 tumour cells. However, IL-2 or IFN-alpha did not enhance NK cell activity in patients who had severely depressed levels of NK cell activity. Interestingly, in some patients, differential responsiveness to IL-2 and IFN-alpha was observed. In some patients, NK cell activity was enhanced by IL-2 but not by IFN-alpha. These results, while only suggestive, may indicate that different populations of NK cells respond preferentially to IL-2 and that IFN-alpha and/or IL-2 enhance NK cell activity in PBL obtained from some, but not all, thermal injury patients. Finally, this study clearly shows that thermal injury patients have defective NK cell activity not only against K562 tumour cells but also against virus-infected cells.     

Changes in natural immunity during the course of HIV-1 infection.

The role of natural killer (NK) and lymphokine-activated killer (LAK) cell-mediated cytotoxicity in AIDS has yet to be established. The objective of this study was to determine inducible LAK cell responses at different stages of HIV-1 infection, and specifically to establish the participation of CD8 lymphocytes in these responses. Peripheral blood lymphocytes (PBL) were isolated from healthy seronegative (CDC-0) subjects and HIV-1+ individuals who were clinically asymptomatic (Centre for Disease Control group 2, CDC-2) or symptomatic (CDC-4) with regard to secondary opportunistic infection (OI). LAK cells were generated upon incubation of PBL with IL-2 and their cytolysis of K562 and U-937 targets was determined using chromium release assays. The role of CD8+ lymphocytes as progenitors and effectors of these LAK cell responses was determined by immunomagnetic depletion of CD8+ cells from precursor PBL and LAK cells, respectively. LAK cell-mediated cytotoxicities in HIV-1-infected individuals were reduced compared with seronegative controls without any corresponding changes in the relative proportions of CD56+ (NK) cells among groups. Depletions of CD8+ subsets from either PBL or LAK cells dramatically reduced total LAK cytotoxic responses and LAK activities per unit CD56+ cell in the OI-/CDC-2 seropositive population. No corresponding changes in LAK activities in seronegative control or HIV+/OI+/CDC-4 groups were observed. Levels of LAK activity against K562 targets in CDC-0/HIV- and CDC-4/HIV+ groups correlated with the percentage of CD56+ LAK cells; corresponding LAK activity in the CDC-2/HIV+ group correlated with the percentage of both CD56+ and CD8+ subsets. These findings suggest that adaptive changes in non-MHC restricted cytotoxic responses occur in HIV-1 individuals at early stages post-HIV infection, before the onset of opportunistic infection.     

Interleukin-2 (r-IL-2)-induced lymphokine-activated killer (LAK) cells and their precursors express the VGO1 antigen

Precursor and effector cells of recombinant interleukin-2 (r-IL-2)-induced lymphokine-activated killer (LAK) activity were investigated for their expression of VGO1. Peripheral blood lymphocytes (PBL) from normal donors were purified and separated in a FACS 420 into VGO1⁺-and VGO1^–-cell fractions before and after culture for 96 hr with 100 U/ml of r-IL-2. Their lytic activity against K 562 and Daudi cells was measured in a⁵¹Cr release assay. The majority, if not all, of the LAK effector and precursor cells was VGO1⁺ lymphocytes. The expression of VGO1 by LAK precursor cells remained stable under the culture conditions used in our experiments. VGO1^– lymphocytes cultured with r-IL-2 demonstrated neither LAK-induced activity nor expression of VGO1 antigen.     

Prothymosin α1 modulates lymphokine-activated killer cell activity and IL-2 production by peripheral blood lymphocytes from melanoma patients in vitro

The effects of prothymosin α1 (Pro α1) on the natural killer (NK), lymphokine (IL-2)-activated killer (LAK) cell activity and the phytohaemagglutinin (PHA)-induced IL-2 secretion of peripheral blood T-lymphocytes (PBL) from 34 malignant melanoma patients of all clinical stages were studied in vitro. On average, melanoma patients showed lower NK and LAK cell activities than healthy donors. In particular, patients with metastases revealed an impaired NK cell activity. However, individuals showed a broad range of LAK cell sensitivity to Pro α1 depending, among other factors, on the disease stage. LAK cell activities were not correlated to tumour stage. Patients' impaired LAK cell activity could be restored by Pro α1. Only patients at stage II (regional metastases) responded to Pro α1. The IL-2 secretion from PBL melanoma and healthy donors did not differ; Pro al administration was without any significant effect. However, stage III (distant metastases) PBL expressed significantly lower IL-2 levels, compared to stage I (primary tumours). The highest IL-2 level was found to be associated with tumour stage II. Pro al enhanced the IL-2 secretion from stage I PBL. Therefore Pro α1 administration abrogated the defective LAK cell activity and IL-2 secretion of PBL, mainly from patients at early melanoma stages.     

Age-associated decline in IL-2 and IL-12 induction of LAK cell activity of human PBMC samples

Previously we reported that young and elderly natural killer (NK) cell activity against the standard NK sensitive K562 cell line can be augmented to the same degree by IL-2 and IFN-. We have extended these studies to include IL-12. Similar to IL-2 and IFN-, IL-12 can enhance NK cytotoxicity to the same degree in both young and elderly samples over a wide range of doses and incubation times when K562 cells are used as targets. However, in contrast to our findings with the NK system, we have observed that induction of lymphokine activated killer (LAK) cell activity, as defined by the ability of peripheral blood mononuclear cells (PBMC) samples to lyse the normally NK resistant Daudi cell line, was significantly decreased in the elderly samples compared to young samples. Comparable age-associated differences were observed in LAK activity after induction with IL-2, IL-12, and IFN- at varying doses and incubation times. We hypothesize an age-associated deficiency either in the mechanism of LAK induction or in target cell recognition.     

人LAK细胞的体外抗肿瘤作用

用重组IL-2(rIL-2)以及部分纯化的IL-2(PPIL-2)体外激活人外周血单个核细胞.(PBM),使之形成LAK细胞,然后借助于~(51)Cr释放实验,研究了正常人和肿瘤病人的LAk细胞对传代的肿瘤细胞系和新鲜实体瘤细胞的杀伤能力。实验结果表明:1.二种来源的LAK细胞均能明显杀伤传代的肿瘤细胞系,包括NK敏感的K562细胞和NK抵抗的Daudi细胞。2.采用数种新鲜实体瘤细胞作靶,二种来源的LAg细胞同样具有明显的广谱杀伤力,这证实该群杀伤细胞确系LAK细胞。3.不同来源的实体瘤细胞对LAK细胞的杀伤敏感性不同,表现为杀伤程度上的差异,这似乎提示某些肿瘤对LAK细胞杀伤存在抗性。     

Long-term cultures of human peripheral blood lymphocytes with recombinant human interleukin-2 generate a population of virtually pure CD3+ CD16- CD56- large granular lymphocyte LAK cells.

It has been reported that lymphocytes from peripheral blood (PBL) cultured with interleukin-2 (IL-2) produce predominantly CD16+ lymphokine-activated killer (LAK) cells. We developed a two-step method to generate LAK cells from human PBL in long-term cultures (10-12 days) with recombinant human IL-2 (rhIL-2) and characterized the evolving LAK cell population by testing its phenotype and cytotoxic activity as a function of time. The starting PBL displayed some natural killer (NK) cytotoxicity but no LAK activity. At day 6, the cells were a mixed population of about 80% CD3+ and 6% CD16+ cells. Little proliferation was evident but strong LAK activity was detected. After 10-12 days, major cell expansion had occurred and they were essentially a pure (greater than 90%) CD3+ CD16- CD56- cell population large granular lymphocyte (LGL) by morphology that displayed strong non-MHC-restricted killing activity (greater than 200 lytic units). Over the same period of time, the CD16+ cells had almost completely regressed in these cultures. This preferential induction of CD+ LAK cells was not an effect of IL-2 concentration as 10 U/ml was as effective as 500 U/ml. Further characterization revealed a major population of CD4+ (60%) and CD8+ (30%) with a smaller fraction (less than 9%) of gamma delta + cells. These results indicate that a virtually pure CD3+ LAK cells population was produced with long-term cultures of lymphocytes from peripheral blood in rhIL-2, in which active proliferation of the CD3+ but not CD16+ cells occurred.     

Combination chemo-immunotherapy: kinetics of in vivo and in vitro generation of natural killer cells and lymphokine-activated killer cells in the rat.

Rats received a single high dose of cyclophosphamide (Cy) (150 mg/kg), followed 48 h later (on day 0) by immunization with a T cell-dependent soluble antigen, ovalbumin in Freund's complete adjuvant (FCA). The effect of this treatment on lymphoid cell subpopulations in the spleen, natural killer (NK) cell and interleukin-2 (IL-2) induced lymphokine-activated killer (LAK) cell activity was examined. Cy (with and without ovalbumin) caused a large relative increase (by day 14) in splenic OX8+, OX19- cells with NK morphology. A marked relative increase in fresh NK cell activity was noted after Cy + ovalbumin, but not consistently after Cy alone. Elevated NK activity was Cy dose- and time-dependent, was evident within 7 days post Cy/ovalbumin and persisted for at least 28 days. Pooled splenic mononuclear cells (MNC), obtained 14 days after Cy/ovalbumin, lost all cytolytic activity against YAC-1 cells when cultured in the absence of human recombinant IL-2 (rIL-2). In contrast, similarly maintained cells from normal rats displayed NK activity higher than normal 'fresh' levels. Upon culture in medium containing 500 U/ml rIL-2, however, 'augmented' NK activity was equivalent, on a per-cell basis, in both normal and Cy/ovalbumin-pretreated groups. LAK activity generated in vitro (i.e. against NK-resistant target cells) was significantly lower in the latter group, and the overall yield of cells was reduced. By day 21 after Cy/ovalbumin, augmented NK activity was significantly greater than controls, on a per-cell and total culture yield basis. Moreover, LAK activity was now similar between groups. It is concluded that the chemotherapy/immunization protocol which we have used can greatly enhance NK activity in vivo and that these cells are responsive to induction of LAK activity by IL-2 in vitro.     

Impaired susceptibility of human trophoblast to MHC nonrestricted killer cells: implication in the maternal-fetal relationship

Mammalian pregnancy has frequently been termed "Nature's allograft," and there is developing evidence that the placental trophoblast cells in their key position at the maternal fetal interface are responsible for escape mechanisms to the maternal immune system. In this paper, we show impaired susceptibility of human trophoblastic tumor cells to major histocompatibility complex (MHC) nonrestricted cytotoxicity systems such as natural killer (NK) cells and lymphokine-activated killer (LAK) cells. LAK cells were induced by the culture of peripheral blood mononuclear lymphocytes (PBL) in recombinant interleukin-2 (rIL-2). Among 21 cultured cell lines derived from various tissues and organs tested, five choriocarcinoma-derived cell lines gave decreased levels of LAK lysis. Cold-target inhibition study and trinitrophenyl (TNP) modification experiment clearly indicated that the impaired sensitivity of trophoblast cells to LAK lysis is due to the decrease of a common target molecule recognized by LAK effector cells. It is suggested that the impaired susceptibilty of trophoblast to MHC nonrestricted killer cells should be functional for the survival of the semiallogeneic fetus.     

Interleukin-2 induced killer cell activity against Epstein-Barr virus-immortalized human B cells

Interleukin-2 (IL-2) activated killer (LAK) cells, generated in vitro by treating peripheral blood lymphocytes (PBL) with human IL-2, are able to lyse a wide variety of target cells without restriction by major histocompatibility complex (MHC) molecules. Earlier observations from this and other laboratories indicated that patients with Epstein-Barr virus (EBV) induced infectious mononucleosis, a self-limiting viral disease, have high EBV-nonspecific natural killer (NK) cell activity. Since the effect of LAK cells on EBV-immortalized B lymphocytes has not yet been studied, we decided to investigate LAK cell activity against autologous and heterologous B lymphocytes immortralized in vitro by EBV and other EBV genome-positive and -negative targets of malignant origin. LAK activity was determined by ⁵¹Chromium release assay. The results obtained show that LAK activity was not specific for EBV and was not MHC-restricted. Results of experiments using NK cell reactive monoclonal antibodies suggest that the cytotoxicity is due predominantly to activated NK cells. Our observations suggest that LAK cells may be very effective for immunotherapy in patients with chronic or progressive EBV infections and EBV-induced lymphoproliferative diseases.     

In vivo boosting of lung natural killer and lymphokine-activated killer cell activity by interleukin-2: comparison of systemic, intrapleural and inhalation routes.

Natural killer (NK) cells are thought to play a role in host defence against malignancy and infection, in immunoregulation and as precursor cells in a generation of lymphokine-activated killer (LAK) cells which can lyse NK-resistant tumour cells. As the lung is a major site for malignancy and infection and as there are large numbers of lymphoid cells including NK cells in the interstitial compartment of the lung, we evaluated the capacity of interleukin-2 (IL-2), a lymphokine capable of augmenting NK activity in vitro, to augment lung NK cell activity in vivo, using different routes of IL-2 administration. We compared both systemic (i.v. and i.p.) and local (intrapleural and inhalation) routes of IL-2 administration (50,000 U/daily for 5 days) using CBA mice, assessing NK and LAK cell activity in the spleen (systemic) and in the lung. The target cells used for these studies were the YAC-1 (NK-sensitive) and P815, NO36 and HA56 (NK-resistant, LAK-sensitive) cell lines. Splenic NK activity was increased by 1.4-1.9-fold for i.v./i.p., respectively, compared with controls with both systemic routes of administration, and lung NK activity was increased 3.2-fold and 3.8-fold (i.v./i.p, respectively, P less than 0.05), to levels which were comparable to systemic (splenic) NK activity following the same therapy. Intrapleural IL-2 administration similarly enhanced lung NK activity (3.3-fold) and splenic NK activity (1.3-fold; P less than 0.05 versus controls for both). Surprisingly, inhaled IL-2 suppressed both splenic and lung NK cell activity (84 +/- 8% and 78 +/- 10% suppression, respectively, P less than 0.05). LAK cell activity was also enhanced in the lung by 1.8-8-fold in response to i.v., i.p. and intrapleural IL-2, whereas inhaled IL-2 was ineffective in generating LAK cell activity. These results suggest that the systemic and intrapleural administration of IL-2 effectively boost pulmonary NK and LAK activity whereas inhalation of IL-2 does not. Thus, in clinical situations where boosting of local lung NK or LAK cell activity is desired, these routes of IL-2 administration may be effective.     

Human recombinant IL-4 decreases the emergence of non-specific cytolytic cells and favours the appearance of memory cells (CD4+CD45RO+) in the IL-2-driven development of cytotoxic T lymphocytes against autologous ovarian tumour cells.

As IL-4 and IL-6 have also been reported to promote the development of T lymphocytes such as IL-2, we investigated their role in the development of specific cytotoxic T lymphocytes (CTL) against autologous ovarian tumours in mixed lymphocyte tumour cultures (MLTC). Peripheral blood lymphocytes (PBL) from five ovarian carcinoma (OC) patients were incubated with autologous OC cells at a PBL:OC cell ratio of 20:1 in IL-2 alone (50 U/ml for the first week and 200 U/ml thereafter) or with IL-4 (100 U/ml) and/or IL-6 (5 U/ml). Neither IL-4 nor IL-6 improved lymphocyte proliferation consistently. In contrast, IL-4 reduced significantly the development of LAK activity as assayed against Daudi cell line, and decreased modestly the emergence of natural killer (NK) activity as assayed against K562. This property was not shared by IL-6. The prevention of the development of non-specific cytolytic activity (LAK and NK activities) was much stronger when the MLTC was started with IL-4 in the absence of IL-2 during the first week in culture. A concomitant drop in NKH-1 expression (CD56) was observed. By inhibiting the emergence of non-specific cytotoxicity, IL-4 provided better evidence of the specific cytolytic activity directed at ovarian cells. In parallel, a significant increase in the generation of memory cells (CD4+CD45RO+) was observed with IL-4. In conclusion, in this model, IL-4 added before IL-2 decreases significantly the emergence of non-specific cytotoxic cells, and promotes the generation of memory cells. These properties may be of interest in the design of strategies aimed at obtaining tumour-specific cells for investigational and immunotherapeutic purposes.     

Dissociation of natural killer and lymphocyte-activated killer cell lytic activities in human CD3− large granular lymphocytes

CD3^? large granular lymphocytes (LGL) are known to display natural killer cell (NK) activity without prior sensitization or restriction by major histocompatibility antigens. Upon short-term exposure to interleukin-2, NK cells were shown to acquire lymphocyte-activated killer cell (LAK) activity. The aim of this study was to analyze the characteristics of these lytic activities. Our data indicated that both NK and LAK activities were Ca²⁺ dependent; however, they could be dissociated by a Ca²⁺ channel blocker or a Ca²⁺ channel competitor agent. Moreover, NK activity was associated with granule exocytosis of lytic proteins spontaneously present in CD3^? LGL, the most likely candidate being the pore-forming protein perforin. By contrast, LAK activity was found to be dependent on de novo protein synthesis and distinct from granule exocytosis. Our results strongly suggest that NK and LAK activities could be defined as two distinct pathways involving different lytic mediators.     

慢性乙肝患者杀伤性免疫细胞功能的研究

通过对４４例病毒性肝炎患者Ｔ细胞亚群，ＮＫ细胞活性与ＬＡＫ细胞活性的观察，探讨了在慢性乙型肝炎病毒复制与非复制状态下的杀伤性细胞活性。结果表明：在乙肝病毒的高复制状态下，ＣＤ８＾＋细胞数增加，ＣＤ４＾＋／ＣＤ８＾＋比例显著下降；ＮＫ细胞活性与ＬＡＫ细胞活性也明显低下，且在ＨＢｅＡｇ与ＨＢＶＤＮＡ阳性组中，ＮＫ活性与ＬＡＫ活性的改变与ＨＢｅＡｇ的Ｐ／Ｎ值变化呈显著负相关，而ＮＫ活性与ＬＡＫ活性变化则     

Peripheral blood lymphocytes resistant to Epstein-Barr virus immortalization manifest high natural killer (NK) type activity against NK-resistant target cells

Epstein-Barr virus (EBV) readily immortalizes human peripheral blood lymphocytes (PBL) in vitro. We found recently that PBL from two EBV-seropositive healthy adults were exceptionally resistant to immortalization by EBV. In contrast to PBL from other EBV-seropositive donors sensitive to immortalization by EBV (S-PBL), the "resistant" PBL (R-PBL) respond to EBV infection with an early interleukin-2 (IL-2) synthesis and high interferon gamma (IFN gamma) production. In order to determine whether these differences in cytokine responses between R-PBL and S-PBL could be associated with a detectable difference in lymphocyte cytotoxicity, we compared the natural killer (NK) activity of R-PBL and S-PBL effectors by using both NK-sensitive (i.e. K562) and NK-resistant (i.e. Raji) targets. We found that, while effectors from EBV-infected R-PBL and S-PBL cultures exhibited comparable NK activity against the K562 targets, they differed remarkably in their cytolytic activity against Raji cells. At days 3 and 5 of culture, effectors from EBV-infected R-PBL showed a significantly higher lytic activity against Raji targets, whereas S-PBL did not. Culture of EBV-infected R-PBL and S-PBL effectors in the presence of recombinant IL-2 (rIL-2) for 5 days resulted in increases of their lytic activity against Raji cells, whereas pretreatment of these effectors with recombinant IFN gamma (rIFN gamma) was found to increase only R-PBL cytotoxicity. These results suggest that the resistance of R-PBL to EBV immortalization could be associated with a lymphokine-mediated early cellular cytotoxic response of the NK/LAK (lymphokine-activated killer cell) type against EBV-infected cells.     

Low expression of CD161 and NKG2D activating NK receptor is associated with impaired NK cell cytotoxicity in metastatic melanoma patients

Natural killer (NK) cells play a role in the innate and adaptive antitumor immune responses. The activity of NK cells is regulated by functionally opposing, activating and inhibitory receptors whose balance ultimately determines whether target cells will be susceptible to NK cell mediated lysis. As melanoma is an immunogenic tumor, the effect of immunomodulating agents is consistently investigated. In this study in 79 metastatic melanoma (MM) patients and 52 controls NK activity, expression of activating NKG2D and CD161 receptors and KIR receptors, CD158a and CD158b, on freshly isolated PBL and NK cells were evaluated. Native NK cell activity of melanoma patients in clinical stage I–III and MM patients was determined against NK sensitive K562, NK resistant Daudi, human melanoma FemX, HeLa and HL 60 target tumor cell lines. In addition, predictive pretherapy immunomodulating effect after 18 h in vitro treatments of PBL of MM patients with rh IL-2, IFN-α (IFN), 13-cis retinoic acid (RA) and combination IFN-α and RA was evaluated with respect to NK cell lyses against K562 and FemX cell lines. In this study we show for the first time that low expression of CD161 and activating NKG2D receptors, without increased expression of KIR receptors CD158a and CD158b, as well as a decrease in the cytotoxic, CD16^bright NK cell subset, is associated with a significant impairment in NK cell activity in MM patients. Furthermore, the predictive pretherapy finding that IL-2, IFN, IFN and RA, unlike RA alone, can enhance NK cell activity of MM patients against FemX melanoma tumor cell line can be of help in the design and development of therapeutic regimens, considering that it has recently been shown that low-dose combination of different immunomodulators represents the most promising approach in the therapy of MM.     

Modulation of natural killing by tumor promoters: the regulatory influence of adherent cells varies with the type of target cell

We have analyzed the regulatory effects of two classes of tumor promoters, phorbol diesters and indole alkaloids, on human natural killer (NK) cell activity in vitro. In accordance with previous reports, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibited natural killing against K 562 targets by unseparated mononuclear cells. Here, suppression of NK required the presence of adherent cells (macrophages). Contrary to the results obtained with K 562, tumor promoter-induced suppression of NK activity tested against U 937, another cell line of known NK susceptibility, was independent of the presence of adherent cells. Thus, NK cytotoxicity of effector cells rigorously depleted of adherent and Ia-positive cells was still inhibited when assayed against U 937, while it was generally enhanced when tested against K 562. Identical results were obtained with teleocidin and dihydroteleocidin B, two members of the recently discovered indole alkaloid class of tumor promoters. Therefore, we demonstrate that the regulatory effect of tumor promoters on human NK activity (suppression or stimulation) is determined not only by macrophages at the effector cell level but also by the type of target cell under study.     

Association of decreased T-cell-mediated natural cytotoxicity and interferon production in Down's syndrome

Total peripheral blood lymphocytes (PBL) and isolated subpopulations from children with Down's Syndrome (DS) and age-matched healthy controls were investigated for their (1) natural killer (NK) and antibody-dependent cellular cytotoxic activities, (2) interleukin 2 (IL-2)-induced augmentation of NK activity, (3) lectin-dependent cellular cytotoxicity (LDCC), (4) ability of serum- and culture-derived soluble suppressor factor(s) to inhibit NK activity of normal lymphocytes, and (5) capacity to produce interferon (IFN) against tumor targets in vitro. T lymphocytes from DS patients demonstrated significantly decreased NK activity against K562 target cells compared to controls. DS lymphocytes also demonstrated a significant reduction in LDCC activity and IL-2-induced enhancement of NK activity. Furthermore, the ability of DS lymphocytes to produce IFN in vitro against K562 target cells was also significantly lower than that for normal PBL. Although sera from DS patients showed a significantly greater inhibitory effect on the NK activity of allogeneic normal PBL than normal sera, culture supernates from DS lymphocytes demonstrated suppressive effects comparable to culture supernates from normal PBL. These studies suggest an association between the decreased NK activity of T-cell subpopulations and lower IFN production by PBL from patients with DS.     

Transferrin receptors on tumor and bone marrow cells: Lack of involvement as target structure for natural killer cells

Summary Two different experimental approaches based on the specificity of monoclonal antibodies (mAbs) have been taken to verify the hypothesis that the transferrin receptor (TfR) on proliferating cells serves as a common target structure for natural killer (NK) cells. Thus, by the lysostrip technique the TfR was removed from the surface of K562 and Molt4 tumor cells by incubation with two different anti-TfR mAbs. The effect of removal of the TfR was controlled by uptake of radiolabeled transferrin, and by binding of non-cross-reacting monoclonal anti-TfR receptor antibodies. Though the modulation of TfR on the membrane of viable cells was nearly complete, the cells remained fully susceptible to NK lysis. The second approach consisted in removal of TfR-bearing cells from bone marrow cell suspensions by an indirect rosetting technique. Using mAbs bound to ox erythrocytes the rosetted TfR-bearing cells could be removed from bone marrow cell suspension by density centrifugation with an efficiency of >99%. It could be shown that both fractions, TfR⁺ and TfR^– cells, could be lysed to the same degree by NK cells. Thus, the evidence obtained speaks against a role of TfR as a recognition structure for NK cells.Abbreviations BM Bone marrow - mAb Monoclonal antibody - NK cell Natural killer cell - PBL Peripheral blood mononuclear cell - TfR Transferrin receptor This work is dedicated to Professor Hans Dierk Waller on the occasion of his 60th birthdayThis work was supported in part by the Deutsche Forschungsgemeinschaft, Bonn, SFB 217