Defective Natural Killer Cell Research Articles

Dysfunction of natural killer cells in human immunodeficiency virus-infected children with or without Pneumocystis carinii pneumonia

The development of Pneumocystis carinii pneumonia (PCP) in human immunodeficiency virus (HIV)-infected children with normal T-cell numbers is contrary to previous experience with HIV-infected adults, in whom low CD4+ T-cell numbers predict susceptibility to PCP. To determine whether PCP in HIV-infected children reflects a qualitative T-cell or other immune defect, we studied four HIV-infected children who also had PCP and 10 others without PCP for T-cell and natural killer (NK) cell function. Most of the HIV-infected children had normal T-cell numbers for age, and all had CD4+ T-cell numbers greater than those predictive of PCP in HIV-infected adults. All HIV-infected children had normal T-cell function in vitro. The HIV-infected children as a whole had deficient NK cell cytolysis. We obtained a significant interactive effect of age by health status for NK cell function between patients and age-matched control subjects. All HIV-infected children with defective NK cell function failed to enhance their NK cell cytolysis when their mononuclear cells were stimulated with recombinant interferon alfa (r-IFN-alpha). This NK cell defect in HIV-infected children may facilitate the development of secondary infection.

Mechanisms accounting for the impaired natural-killer cell activity in refractory anaemia with excess of blasts.

Natural killer (NK) cells were analyzed in 38 untreated patients with refractory anaemia with excess of blasts (RAEB), using cytotoxicity assays and immunofluorescence with monoclonal antibodies. We found that patients with RAEB have normal numbers of peripheral blood and bone marrow NK cells. NK cells from RAEB patients express very low natural-killer cell activity (NKa) which may be increased significantly with recombinant alpha-interferon and recombinant interleukin-2, although it remains below the lower limit of the control range. The cells exhibit normal tumour cell binding capacity, but fail to release sufficient amounts of natural-killer cytotoxic factors (NKCFs) upon their interaction with NK-sensitive K562 cell targets or their stimulation with phytohaemagglutinin. Our results suggest that defective NKa in RAEB patients may be due, at least in part, to impaired release of functionally active NKCFs. This disturbance is probably the result of some intrinsic defect of RAEB NK cells in NKCF production, storage, and/or release. The possibility of an impairment in the activation signal provided by the stimulatory K562 cells cannot be excluded, although it seems unlikely. We postulate that this abnormality might represent a manifestation of dysplastic haemopoiesis. Further studies are certainly needed to investigate whether other defective mechanisms are also implicated in the determination of the low NKa in patients with RAEB.

Role of Natural Killer Cells in Resistance to Systemic Cryptococcosis

These studies demonstrate that Cryptococcus neoformans infection induced a dose-dependent augmentation of splenic natural killer (NK) cell activity by bg/+, but not bg/bg mice. To directly assess the role of NK cells in resistance to C. neoformans, bg/+ and bg/bg mice were treated with anti-NK-1.1 monoclonal antibody (mAb). Anti-NK-1.1-treatment abrogated the augmented NK cell activity observed during C. neoformans infection in bg/+ mice. Anti-NK-1.1-treated bg/+ mice had higher C. neoformans colony forming units (CFU) in their lungs on days 3 and 7 after intravenous (i.v.) challenge than control bg/+ mice. Moreover, the number of C. neoformans CFU in the lungs of anti-NK-1.1-treated bg/+ mice on days 3 and 7 were similar to those observed for infected bg/bg mice. By day 14, however, no differences in C. neoformans CFU were evident in the lungs of anti-NK-1.1-treated and control bg/+ mice. Anti-NK-1.1-treatment did not alter either the growth of C. neoformans in the spleens, livers, kidneys, or brain of bg/+ mice or the susceptibility of bg/bg mice to systemic cryptococcosis. These studies suggest that NK cells do not play a role in resistance to systemic cryptococcosis in the spleen, but do appear to play an early, but transient role in resistance to C. neoformans in the lungs. Overall, congenital defects in polymorphonuclear neutrophils (PMNs) and macrophages (M phi s), in addition to defects in NK cells, contribute to the enhanced susceptibility of bg/bg mice to systemic cryptococcosis.

Differential staphylococcal protein a-induced enhancement of natural killer cell activity of lymphocytes from HIV-seropositive individuals

A decrease in Natural Killer (NK) cell activity is a common feature of the immune dysfunction found in patients with HIV-induced acquired immune deficiency syndrome (AIDS). We and others have shown earlier that staphylococcal protein A (SpA) preparations enhance NK cell activity against tumor targets. The present study was aimed at exploring whether the decreased NK activity of lymphocytes from HIV seropositive subjects could be modulated or restored in vitro by SpA. Two types of HIV-seropositive subjects were studied: hemophiliac and non-hemophiliac; matched controls were chosen among hospital staff and HIV-seronegative hemophiliac volunteers. In vitro proliferation and interleukin-2 (IL-2)/interferon gamma (IFNγ) release in response to mitogens were also studied. NK cell responses of peripheral blood lymphocytes (PBL) of HIV-seropositives were lower than those of seronegatives. However, exposure of PBL from HIV-seropositive individuals to SpA boosted their NK cell responses against NK-resistant target cells of tumor origin. The decrease in NK activity could not be attributed to the low number of NK cells, since no significant difference in NK cell number was observed between HIV-seropositive individuals and controls. Mitogen-induced blastogenic responses were present in all four groups, as was the mitogen-induced IFNγ release. We conclude that impaired NK activity and its boosting against NK-resistant targets after SpA induction is an important characteristic of lymphocytes of HIV-seropositive individuals regardless of the disease state and that this NK defect may not be irreversible. Our experimental model appears to open the door for mechanistic and molecular studies of the NK cell defect as well as for devising a new strategy for an immunotherapeutic approach to boost NK activity in HIV-infected subjects.

Interferon System and Natural Killer Cell Activity in Myasthenia Gravis

The autoimmune response in myasthenia gravis is well characterized, but little is known about the mechanisms initiating it. We have studied the interferon system and natural killer cell activity in 25 patients with myasthenia gravis and compared them to 68 healthy subjects and 96 patients with acute viral infections. Forty-four per cent of patients had circulating interferon (greater than 16 mu/ml), and in a similar proportion their peripheral blood mononuclear cells were in an antiviral state, i.e., showed low levels of viral replication when infected by vesicular stomatitis virus. Spontaneous in vitro interferon production by patients' peripheral blood mononuclear cells was also common (greater than 10 mu/ml, 32 per cent), while the response to the alpha-interferon inducer poly I:C was lower than expected, possibly reflecting the already high state of activation of the interferon system. These results were essentially similar to those obtained in patients with viral illnesses and differed significantly from healthy controls. In many myasthenia gravis patients (16 of 22, 73 per cent), a markedly deficient natural killer cell activity was found, with a median cytotoxicity of 6.5 per cent compared to 29 per cent in healthy subjects (p less than 0.005). Thus, many patients with myasthenia gravis have evidence of an activated interferon system and defective natural killer cell activity, suggesting an occult viral infection or reflecting nonspecific stimulation which may nevertheless contribute to the pathogenesis of the autoimmune response.

Cytotoxicity of purified leu 19+ cells from the peripheral blood of children with acute lymphocytic leukemia

Several investigators have reported decreased natural killer cell activity of the peripheral blood from children with acute leukemia both at diagnosis and in relapse. This study was to determine whether this decreased natural killer activity is the result of a diminished number or defective function of natural killer cells or both. The percentage of Leu 19+ (NKH-1, CD56) and the lytic activity of a purified Leu 19+ population from the peripheral blood of children with acute lymphocytic leukemia as well as from healthy children were determined. This cell population mediates most natural killer and natural killer-like activity in the peripheral blood. Twenty-three children with acute lymphocytic leukemia (16 at diagnosis, seven in relapse) as well as six control children were studied. The percentage of Leu 19+ cells was significantly lower in the blood of children either at initial diagnosis (median, 3%; P less than 0.005) or in relapse (median, 1%; P less than 0.01) than that for the control children (median, 12.5%). The cytotoxicity of peripheral blood mononuclear cells (PBMC) against K562 in 3-hour 51Cr release assay was significantly lower for patients either at diagnosis (median, 8.5 lytic units[LU]/10(7) cells; P less than 0.005) or in relapse (median, 3 LU/10(7) cells; P less than 0.005) than that for normal controls (median, 97 LU/10(7) cells). The lytic activity of a fluorescent activated cell sorter (FACS) purified Leu 19+ population was evaluated. The Leu 19+ cells were sorted from PBMC of 11 children with acute lymphocytic leukemia who had more than 2% Leu 19+ cells in their PBMC (nine at diagnosis and two in relapse). The lytic activity of sorted Leu 19+ cells was significantly (P less than 0.04) lower for patients at initial diagnosis (median, 45 LU/10(7) cells) than that for normal control children (median, 317 LU/10(7) cells). One of the two children studied at relapse had low Leu 19+ lytic activity. The authors concluded that (1) The percentage of Leu 19+ cells in the peripheral blood of the majority of children with acute lymphocytic leukemia either at diagnosis or in relapse is below normal; (2) The lytic activity of PBMC from the majority of children with acute lymphocytic leukemia is reduced both at diagnosis and in relapse; and (3) The lytic activity of Leu 19+ purified PBMC is reduced in the majority of children with acute lymphocytic leukemia. These findings confirm the defective natural killer cell profile in children with acute lymphocytic leukemia both at the time of diagnosis and in relapse.

Defective interferon-augmented natural killer cell activity in patients with metastatic malignant melanoma

Unstimulated and interferon (IFN)-stimulated natural killer cell (NK) activity was investigated in patients with malignant melanoma prior to the removal of the primary melanoma (stage I disease) or in patients with melanoma metastases. Unstimulated as well as IFN-stimulated NK activities, directed against the primarily NK-sensitive K562 cell line, were found not to differ significantly from the NK activity of healthy control subjects. In contrast, IFN-stimulated NK activity directed against the primarily NK-insensitive Chang hepatoma and JY cell lines was significantly lower in patients with metastatic melanoma than in patients with non-metastatic disease (Chang hepatoma cell line: P less than 0.02; JY cell line: P less than 0.0017) and - in experiments using the JY cell line - than in healthy controls (P less than 0.01). Stage I melanoma patients did not differ in their IFN-induced NK activity from healthy control subjects using Chang hepatoma and JY cell lines. Finally, the IFN-induced increase in NK activity directed against primarily NK-insensitive target cell lines was significant in stage I melanoma patients and in healthy controls (P less than 0.01, respectively), but not in patients with metastatic melanoma (P greater than 0.5). We thus conclude that patients with metastatic malignant melanoma exhibited a defect in IFN-augmented NK activity directed against primarily NK-insensitive targets.

Defective natural killer cell activity in primary Sjögren's syndrome. An investigation of natural killer cytotoxic factor and in vivo membranebound IgG: [formula omitted], BK Pedersen, Department of Rheumatology TTA, Rigshospitalet, University of Copenhagen and Bartholin Institute, Municipal Hospital, Copenhagen, (Denmark)

Defective natural killer cell activity in primary Sjögren's syndrome. An investigation of natural killer cytotoxic factor and in vivo membranebound IgG: [formula omitted], BK Pedersen, Department of Rheumatology TTA, Rigshospitalet, University of Copenhagen and Bartholin Institute, Municipal Hospital, Copenhagen, (Denmark)

Defective natural killer cell activity in puerperal hyperprolactinemia

Prolactin (PRL) influences immune reactivity in animals and in humans and both T-cell abnormalities and reduced natural killer (NK) cell activity have been reported in women with pathological hyperprolactinemia. To investigate further the possible interactions between PRL and the immune system in humans, we analysed T-cell phenotypes and NK cell activity in 15 women with physiological hyperprolactinemia of the puerperium and in 45 age-matched healthy normal cycling women. Puerperal women displayed a normal T-cell phenotype but a significant reduction in the number of Leu-7+ and Leu-11+ cells, associated with a decreased NK cell activity, as measured against K-562 target cells. There was a significant inverse correlation between the raised serum PRL levels and both the number of Leu-7+ cells and NK cell activity. These data confirm an important immunoregulatory role for PRL in humans and suggest a direct inhibitory effect of the chronically raised PRL concentrations on the maturation of NK cells.

Mechanism of defective natural killer cell activity in patients with AIDS is associated with defective distribution of tubulin

Abstract Previous studies have demonstrated the importance of some cytoskeleton components in killing mechanisms. In fact, a microtubule and microfilament (MF) rearrangement in the lytic sequence of CTL and NK cells has been observed. In particular, MF seem to be related to the binding phase, because MF inhibitors suppress the binding of NK cells to the target, whereas microtubule inhibitors suppress only the killing phase. In this paper, the distribution of two cytoskeleton components, actin and alpha- and beta-tubulin, has been studied in PBL from AIDS patients, who maintain the capacity to bind to the target cell line K562 but are not able to kill it. PBL were labeled with mAb to these two cytoskeleton components, and then indirect immunofluorescence was used to visualize their distribution in the conjugates. A normal polarization of actin in the effector PBL was found, whereas no tubulin rearrangement was evident in the effector and target cells. On the contrary, in conjugates of PBL or large granular lymphocytes from normal donors and K562, a polarization of actin in the effector cell and a polarization of tubulin both in the effector and in the target cells, at the site of the attachment, was evident. These data suggest that a deficiency of tubulin rearrangement may underlie the inability of the NK cells from AIDS patients to kill their target.

Mechanism of defective natural killer cell activity in patients with AIDS is associated with defective distribution of tubulin.

Previous studies have demonstrated the importance of some cytoskeleton components in killing mechanisms. In fact, a microtubule and microfilament (MF) rearrangement in the lytic sequence of CTL and NK cells has been observed. In particular, MF seem to be related to the binding phase, because MF inhibitors suppress the binding of NK cells to the target, whereas microtubule inhibitors suppress only the killing phase. In this paper, the distribution of two cytoskeleton components, actin and alpha- and beta-tubulin, has been studied in PBL from AIDS patients, who maintain the capacity to bind to the target cell line K562 but are not able to kill it. PBL were labeled with mAb to these two cytoskeleton components, and then indirect immunofluorescence was used to visualize their distribution in the conjugates. A normal polarization of actin in the effector PBL was found, whereas no tubulin rearrangement was evident in the effector and target cells. On the contrary, in conjugates of PBL or large granular lymphocytes from normal donors and K562, a polarization of actin in the effector cell and a polarization of tubulin both in the effector and in the target cells, at the site of the attachment, was evident. These data suggest that a deficiency of tubulin rearrangement may underlie the inability of the NK cells from AIDS patients to kill their target.

Decreased Blood Natural Killer Cell Activity and Immunoglobulin Synthesis in vitro in Aplastic Anemia

Natural killer (NK) cell numbers and T lymphocyte subpopulations in peripheral blood were evaluated in six patients with aplastic anemia (AA). The immunophenotyping results were correlated to in vitro tests of NK cell cytotoxicity against K562 cells and of immunoglobulin (Ig) production after pokeweed mitogen (PWM) stimulation. A significant decrease was found both in the percentage of Leu 11 positive cells and in NK cell activity as compared to age- and sex-matched healthy controls. The decrease in NK cell activity could not be entirely compensated by an increase in effector/target cell ratios, thus suggesting not only a quantitative but also a functional defect in NK cells of the AA patients. Three of four AA patients tested showed no major increase of Ig production after PWM stimulation. All these three patients also had fewer "functional T helper" cells (Leu3+/Leu8-) and increased numbers of T suppressor/cytotoxic cells (Leu2+) when compared to controls. No significant differences in numbers of B lymphocytes (B1+) could be found. Our findings suggest a possible linkage between quantitative and qualitative abnormalities in lymphocyte subsets in aplastic anemia. However, no evidence was found to support the hypothesis of increased NK cell activation behind the hemopoietic depression in this disease.

Depressed natural killer cell activity in uremia. Evidence for immunosuppressive factor in uremic sera.

We investigated the natural killer (NK) cell activity of peripheral blood mononuclear cells (PBMC) and the suppressive factor of NK cell activity in patients on maintenance hemodialysis (HD). NK cell activity was significantly lower in patients on HD than in healthy controls (20.2 +/- 16.5 vs. 31.0 +/- 13.2%, p less than 0.01). There was no difference in NK cell activity between patients treated with cuprophane and high-permeability membrane. NK cells from patients on HD showed a poor response to interleukin-2, and uremic sera significantly suppressed NK cell activity of normal PBMC. Although urea, creatinine, methylguanidine or guanidinosuccinic acid alone did not suppress the NK cell activity of normal PBMC, the guanidino compound did so significantly. It is suggested that defective NK cell activity in uremic patients explains in part their susceptibility to malignancy and infection. The immunosuppressive effect may be exhibited by synergism or mosaic of uremic toxins.

Natural killer cells in chronic leukemia. Function and markers.

Twenty-two patients with chronic lymphocytic leukemia (CLL) and 14 patients with chronic myelogenous leukemia (CML) were studied with respect to natural killer (NK) cell activity and related cell markers (Leu 7 and Leu 11b). Significantly reduced NK cell activity was detected in peripheral blood from the patients with CLL. Similarly, a reduced number of cells with the markers Leu 7 and Leu 11b (CD 16) were detected in the same patients. Removal of the leukemic cells by centrifugation of cells forming rosettes with mouse erythrocytes led to an augmented, but not fully normalized, NK activity. This indicates that the low NK activity in CLL partly may be due to overgrowth of leukemic cells. However, in spite of the lymphocytic infiltration, the NK cell activity in the bone marrow of CLL patients did not differ significantly from that of normal controls. The patients with CML in the chronic phase as well as patients in the accelerated or blast phase also had a reduced NK activity. The finding that patients in the chronic phase had a reduced NK activity and normal numbers of Leu 11b (CD 16) positive cells, together with no detectable blasts in the peripheral blood, indicates that patients with CML may have an inherent NK cell defect. The highly reduced activity found in patients with the accelerated/blast form may in addition partly be due to overgrowth of leukemic cells. This low NK activity may be of importance in the development of chronic leukemia.

Mechanism of defective NK cell activity in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex. II. Normal antibody-dependent cellular cytotoxicity (ADCC) mediated by effector cells defective in natural killer (NK) cytotoxicity.

Our studies and other investigations have shown that NK effector cells can also mediate antibody-dependent cellular cytotoxicity (ADCC) through the use of the Fc gamma receptor on the NK cell membrane. Peripheral blood lymphocytes (PBL) derived from patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex exhibit a poor NK activity due to a defective "trigger" required for activation in the lethal hit stage of the NK lytic pathway. Consequently, it was important to delineate whether the defect in AIDS NK cells affected the ADCC function. By using the 51Cr-release assay, the ADCC cytotoxic activity of AIDS PBL was found to be within the normal range, despite the absence of significant NK activity. Several experiments corroborated that the same effector cells mediate both NK CMC and ADCC. Depletion of Fc gamma R-bearing cells resulted in elimination of both the ADCC and NK cytotoxic functions. Single cell analyses, using one- and two-target cell conjugates, revealed that the frequency of ADCC effector:target conjugates and the frequency of killer cells from AIDS PBL were comparable to the frequencies seen in the normal controls. However, when mixtures of NK and ADCC targets were used to form mixed two-target conjugates, the AIDS effector cells lysed only the bound ADCC target, whereas the normal effector cells lysed both the bound NK and ADCC targets. These results demonstrate clearly that the same NK/K effector cells from AIDS PBL, defective in NK activity, are not impaired in mediating ADCC activity. These findings were supported by the demonstration that AIDS PBL stimulated with ADCC targets, but not with NK targets, released NK cytotoxic factors, postulated mediators of the NK CMC reaction. These findings indicate that the NK/K cells in AIDS are triggered normally for ADCC activity but are not triggered for NK activity. Furthermore, the results indicate that the lytic machinery is not impaired in the AIDS NK/K cells.

A killing defect of natural killer cells with the absence of natural killer cytotoxic factors in a child with Hodgkin's disease

A killing defect of natural killer (NK) cells in the absence of NK cytotoxic factors (NKCF) was first demonstrated in a child with Hodgkin's disease. The patient lacked detectable NK cell activity in every phase of the disease as measured by a four-hour 51Cr-release assay using K562 cells as a target. The percent lysis at a 40:1 effector:target ratio by the patient's lymphocytes was persistently below 0.3% as compared with the normal lymphocyte value of 46.2% +/- 5.8% (mean +/- SD). NK cell activity was not detectable at effector:target ratios of 10:1 to 80:1 and by prolongation of the incubation time, and the NK cell defect was not restored or improved by lymphocyte stimulation with polyinosinic-polycytidilic acid, interferon (IFN)-alpha, or interleukin 2 (IL 2). The numbers of Leu-7+ cells and Leu-11+ cells were normal as counted by flow cytometry. A single cell- in-agarose assay demonstrated normal numbers of target binding cells (TBCs), and they showed the morphology of “large granular lymphocytes.” However, there were no TBCs with dead targets. These results indicated that the patient's lymphocytes contained normal numbers of NK cells that were capable of recognizing and binding to a target but were incapable of killing the bound target cell. The patient's lymphocytes were then studied for their release of NKCF upon interaction with K562 cells. The patient's cells did not release NKCF, and the NK cell defect was not restored or improved by stimulation of the cells with IFN or IL 2. It is suggested that the deficient release of NKCF may have been related to the killing defect of the NK cells in this patient.

A Killing Defect of Natural Killer Cells With the Absence of Natural Killer Cytotoxic Factors in a Child With Hodgkin’s Disease

A killing defect of natural killer (NK) cells in the absence of NK cytotoxic factors (NKCF) was first demonstrated in a child with Hodgkin's disease. The patient lacked detectable NK cell activity in every phase of the disease as measured by a four-hour 51Cr-release assay using K562 cells as a target. The percent lysis at a 40:1 effector:target ratio by the patient's lymphocytes was persistently below 0.3% as compared with the normal lymphocyte value of 46.2% +/- 5.8% (mean +/- SD). NK cell activity was not detectable at effector:target ratios of 10:1 to 80:1 and by prolongation of the incubation time, and the NK cell defect was not restored or improved by lymphocyte stimulation with polyinosinic-polycytidilic acid, interferon (IFN)-alpha, or interleukin 2 (IL 2). The numbers of Leu-7+ cells and Leu-11+ cells were normal as counted by flow cytometry. A single cell-in-agarose assay demonstrated normal numbers of target binding cells (TBCs), and they showed the morphology of "large granular lymphocytes." However, there were no TBCs with dead targets. These results indicated that the patient's lymphocytes contained normal numbers of NK cells that were capable of recognizing and binding to a target but were incapable of killing the bound target cell. The patient's lymphocytes were then studied for their release of NKCF upon interaction with K562 cells. The patient's cells did not release NKCF, and the NK cell defect was not restored or improved by stimulation of the cells with IFN or IL 2. It is suggested that the deficient release of NKCF may have been related to the killing defect of the NK cells in this patient.

Natural killer (NK) cell immunodeficiency in patients with chronic myelogenous leukemia. II. Successful cloning and amplification of natural killer cells.

Defective natural killer (NK) cell populations from patients with chronic myelogenous leukemia (CML), that reacted with both HNK-1+ and B73.1+ antibodies, were obtained by a fluorescence-activated cell sorter (FACS). These fractions, along with NK fractions from normal donors which reacted with both antibodies, were expanded as bulk cultures or clones by limiting dilution, for 4 weeks in the presence of 10% interleukin 2 (IL 2), human type AB plasma, and irradiated human allogeneic mononuclear cells. Successfully established clones from patients with CML, with lytic activity against autologous and more differentiated neoplastic granulocytes, were generated more efficiently from B73.1+ than from HNK-1+ subsets. However, there were no significant differences among the generations of B73.1+ and HNK-1+ clones for both patients and normal donors with lytic activity against NK susceptible K-562 targets. Fresh myeloblast preparations from a blast crisis were found to be more susceptible to lysis by IL 2-proliferative B73.1+ and HNK-1+ clones than were fresh myelocyte preparations from a chronic phase CML patient, which were lytically susceptible to only B73.1+ clones. B73.1+ and HNK-1+ subsets from CML patients demonstrated major histocompatibility complex nonrestricted killing, and showed the following predominant phenotypes: B73.1+T3+T8+ or B73.1+T3+T8- from B73.1+ subsets; and HNK-1-T3+T8+ (initially HNK-1+) from HNK-1+ subsets. In contrast, B73.1+ and HNK-1+ clones from normal donors showed the following predominant phenotypes: B73.1+T3-T8-; and HNK-1-T3-T8- or HNK-1-T3-T8+ (initially all HNK-1+). Short-term in vitro IL 2 or interferon treatment of fresh NK defective subsets from CML patients resulted in minimal cytotoxic augmentation. In contrast, defective NK cells from CML patients, whether HNK-1+ or B73.1+ subsets, proliferated with complete regeneration of cytolytic activity after a 3-4 week exposure to IL 2, but differed in phenotypic profiles as compared to those of normal donors. These observations imply that not only fresh defective NK cells but also the cytotoxically restored clones from CML patients are derived from different NK subsets and may represent undifferentiated forms of NK cells that may be arrested at an early stage of development by yet unknown mechanism(s). In vitro substantiation of autologous leukemia cell killing by IL 2-proliferative NK cell clones is encouraging and may allow for new in vivo immunotherapeutic modalities in CML patients.

Human Schistosomiasis: Deficiency of Large Granular Lymphocytes and Indomethacin‐Sensitive Suppression of Natural Killing

Twenty-eight children infected with Schistosoma haematobium and S. mansoni were tested for natural killer (NK) cell activity in vitro using the myeloid/erythroid cell line K562 as target. In addition, the frequency of large granular lymphocytes (LGL) and the number of HNK-1+ lymphocytes were examined in peripheral blood. NK cell activity was found to be markedly reduced in most patients when compared with a group of healthy Caucasian individuals (P less than 0.005). Moreover, the impairment of NK activity clearly correlated with the intensity of infection, which was quantified by parasite ova excretion in stool and urine. Within the lymphocyte compartment the percentages of cells with the NK phenotype (HNK-1+) were found to be normal, although the majority of patients exhibited decreased numbers of LGL (P less than 0.005). The absolute and relative frequencies of LGL and HNK-1+ lymphocytes by no means correlated with the parasite load. In vitro results suggest an at least partly prostaglandin-mediated and interferon-resistant functional defect of NK cells.

Impaired natural killer cell recycling in childhood chronic neutropenia with morphological abnormalities and defective chemotaxis of neutrophils

Natural killer (NK) cell activity was measured by a 51Cr-release assay using K562 target cells in 12 neutropenic children. NK cell activity was depressed in four patients who had childhood chronic neutropenia with abnormal neutrophil morphology and chemotaxis. The percentage of lysis at a 40:1 effector-target ratio was 28.4% to 42.1% (P less than .001) of the normal lymphocyte value during the study period (32 to 40 months). NK cell activity was normal in the other eight children with chronic neutropenia without any of these neutrophil abnormalities: lazy leukocyte syndrome, Shwachman syndrome, or dysgammaglobulinemia type I with neutrophil defects. NK cell activity of the four patients was depressed at 5:1 to 40:1 effector-target ratios. The NK cells responded to in vitro interferon (IFN)-alpha and interleukin 2, as did normal lymphocytes, but the activated levels were still lower than those of normal lymphocytes (P less than .01). Because NK cells kill a target through recognition, binding, killing, and detaching, and they repeat this lytic sequence (ie, recycling), the localization of the NK cell defect was further analyzed in the four patients using both 51Cr-release and single cell-in-agarose assays. The patients' NK cells were normal in recognizing, binding, and killing a target but were defective in recycling; the estimated maximum recycling capacity (MRC) values in a four-hour assay were 1.8 to 2.4 (P less than .01), as compared with the normal lymphocyte value of 5.5 +/- 0.6 (mean +/- SD). The stimulation of the effector cells with 1,000 U/mL IFN-alpha did not significantly increase the estimated MRC. These results demonstrate that NK cells are defective in recycling in some type of childhood chronic neutropenia with abnormal neutrophil morphology and chemotaxis. The NK cell deficiency is of clinical interest in terms of its relationship to the recurrent infections, development of malignancy, and dysgranulopoiesis in the disorder.