Biomedical subjects

A D Bankhurst

Publications and source records attributed to A D Bankhurst.

At least 37 records · Page 2Linked to original sources

PubMed1989

Antibacterial activity of human natural killer cells.

The in vitro effects of human NK cells on viability of Gram-negative and Gram-positive bacteria was investigated. PBLs depleted of glass-adherent cells showed a significant antibacterial activity that was increased as the concentration of NK cells became higher. Leu-11-enriched cells exhibited the most efficient bactericidal activity. Stimulation of NK cells with staphylococcal enterotoxin B for 16 h produced a significant increase in the antibacterial activity of all NK cells tested. The antibacterial activity of monocyte-depleted cells and Leu-11-enriched cells was also enhanced after culturing in vitro for 16-24 h without exogenous cytokines. Dependence of the antibacterial activity on the presence of serum in the culture medium was not found. Ultrastructural studies revealed close contact between NK cell membranes and bacteria, no evidence of phagocytosis, and extracellular bacterial ghosts, after incubation at 37 degrees C. Supernatants from purified NK cells exhibited potent bactericidal activity with kinetics and target specificity similar to that of effector cells. These results document the potent antibacterial activity of purified NK cells and suggest an extracellular mechanism of killing.

Adult↗

PubMed1989

Role of mevalonic acid in the regulation of natural killer cell cytotoxicity.

Considerable evidence has accumulated for a role of a nonsteroidal mevalonate product in the regulation of DNA replication and cell division. We report here a similar requirement for mevalonate in a nonreplicative function, that of natural killer (NK) cell cytotoxicity. Treatment of NK cells with 10 microM compactin for 48 hr results in a significant inhibition of cytotoxicity which can be completely reversed by treatment with 1 mM mevalonate, but not cholesterol, dolichol, or isopentenyl adenine. Protein and RNA synthesis appear to be involved in this reversal. Treatment with compactin and reversal with mevalonate do not affect the phenotypic distribution of the effector cell population, and the cell type involved in the inhibition and reversal of cytotoxicity is a CD16 (Leu 11)-, Leu 19-positive, large granular lymphocyte. The conjugation of the target and effector cell early in the lytic pathway is inhibited by compactin treatment of the effector cell population, and this inhibition is reversed by mevalonate.

Cell Line↗

PubMed1989

The mechanisms involved in the activation of human natural killer cells by staphylococcal enterotoxin B.

The induction of enhanced natural cytotoxicity from human peripheral mononuclear cells by staphylococcal enterotoxin B (SEB) was examined. The activated killer cytotoxicity (AKC) was maximum at 16 hr with 1 mg/ml SEB. The precursor and effector cells of AKC were determined to be primarily CD5 negative, CD8 negative, CD16 positive cells. Monocytes and interleukin-1 played no role in the generation of AKC. However, a major role for interleukin-2 (IL-2) in AKC was shown by the inhibition of AKC when anti-IL-2 antibody or cyclosporin was added to the induction cultures. SEB rapidly induced the production of IL-2 from glass nonadherent cells by 6 hr and reached peak levels by 24 hr (162 U/ml). IL-2 induced by SEB in these induction cultures was preferentially produced by CD16 positive cells. Even though interferon-gamma (IFN-gamma) production was induced in these cultures, no role for IFN could be shown in SEB-induced AKC.

Antigens, Differentiation↗

PubMed1989

Suppression of lymphoid cell function in vitro by inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase by lovastatin.

A 3-hydroxy-3-methylglutaryl Coenzyme A (HMG CoA) reductase inhibitor, lovastatin, has recently been approved for the treatment of hypercholesterolemia. However, the product of HMG CoA reductase, mevalonate (MVA), is an early precursor not only for cholesterol but also for several other essential molecules. Since HMG CoA reductase is found in lymphoid cells, the potential alteration of lymphoid cell function by lovastatin was examined. At doses equivalent to pharmacological concentrations, exposure to lovastatin for 7 days inhibited phytohemagglutinin-stimulated proliferation by 25-54% and natural killer cell cytotoxicity by 25-57%. At higher concentrations (10 microM) for shorter periods of time (48 h), lovastatin inhibited phytohemagglutin and Concanavalin A-stimulated proliferation by 83% and 38% respectively, natural killer cell cytotoxicity by 93%, and interferon gamma production by 98%. The inhibition of these parameters could be largely reversed by the addition of MVA; however, MVA itself was not a stimulant. Overall, the in vitro inhibitions seen with lovastatin raise a concern about potential in vivo alteration of lymphoid cell function seen with long term administration of HMG CoA reductase inhibitors.

Cytotoxicity, Immunologic↗

PubMed1989

Selective proliferation of natural killer cells among monocyte-depleted peripheral blood mononuclear cells as a result of stimulation with staphylococcal enterotoxin B.

In vitro stimulation of monocyte-depleted peripheral blood mononuclear cells with staphylococcal enterotoxin B (SEB) resulted in selective proliferation of cells which express the phenotypic and functional characteristics of natural killer (NK) cells. This culture system provides an easy method for obtaining highly purified NK cells, by sequential incubation of monocyte-depleted cells with SEB and then with interleukin-2 (IL-2). After culture for 4 to 5 days in the presence of SEB, 98 to 100% of the cells expressed the CD16 (Leu11) and HNK-1 (Leu19) antigens. This purification occurred through the death of lymphocytes lacking NK cell markers and marked proliferation of NK cells themselves, which leads to an enrichment of the NK cell population. Activation of NK cells was detected by the appearance of the gamma interferon receptor and IL-2 receptor antigens. This homogeneous population showed the morphology of large granular lymphocytes, were potent effectors of cell-mediated cytotoxicity against K562 and Daudi tumor cell lines, and were able to kill gram-positive and gram-negative bacteria. IL-2 was necessary to maintain the activation and proliferation after SEB stimulation for 4 days. Moreover, the maximum frequency of binding to K562 cells (60.6%) was similar to that recently found (58 +/- 3%) (P. Garcia-Peñarrubia, F. T. Koster, and A. D. Bankhurst, J. Immunol. Methods 118:199-208, 1989) with fresh and highly purified NK cells. This method can be used as a source of highly purified NK cells to study their functional properties and applications to the treatment of cancer.

Adult↗

PubMed1989

Magnetic resonance and computed tomographic imaging in the evaluation of acute neuropsychiatric disease in systemic lupus erythematosus.

Magnetic resonance (MR) imaging and computed tomography (CT) are useful for the evaluation of central nervous system (CNS) lupus. This report describes the use of cranial MR and CT in 21 patients with systemic lupus erythematosus (SLE) with acute neuropsychiatric symptoms manifested by headache, seizures, focal neurological deficits, psychosis, or organic brain syndrome. Computed tomography was found to be insensitive and detected only diffuse atrophy (two cases), cerebral infarct (one case), and intracerebral haemorrhage (one case) in the 21 patients. Cranial MR images obtained with a General Electric 1.5 tesla Signa unit detected labile and fixed areas of increased proton intensity interpreted as focal oedema (eight cases), infarct (10 cases), haemorrhage (one), atrophy (seven), and acute sinusitis (two). Focal oedema was characterised by labile, high intensity lesions in the gray or white matter of the cerebellum, cerebrum, or brain stem, which completely resolved after aggressive corticosteroid treatment. Most high intensity reversible or fixed lesions evident on MR were not apparent on cranial CT images. In several patients sequential MR images were valuable in monitoring the efforts of treatment. Although histological confirmation of the high intensity brain lesions apparent on MR is desirable, prior necropsy studies suggest that pathological confirmation may be difficult owing to the paucity of recognisable brain lesions in patients with CNS lupus. It is concluded that for the evaluation of acute neuropsychiatric SLE MR is useful and provides more information than cranial CT.

Adolescent↗

PubMed1989

Population distributions of natural killer and K562 target cell conjugates.

We studied the types of conjugates formed at different effector-to-target ratios (R) in the NK-K562 target system. Using purified natural killer (NK) effector cells prepared by a panning technique (greater than 98% CD16), distributions of conjugates are formed such that LTn (one NK cell bound to one or more target cells) are more common at R values less than 1, and LmT (one or more NK cells bound to one target cell) are observed at R greater than 1. Population distributions of these types of conjugates are in agreement with the predictions of the model previously reported for CTL target cell conjugates. In contrast, monocyte-depleted peripheral blood lymphocytes form conjugates in which the LT type is the predominant subpopulation for all values of R. The impact of cell purity on the kinetics and dynamics of cell-mediated cytotoxicity at the population level is discussed.

Adult↗

PubMed1989

The prevalence of anticardiolipin antibodies in a healthy elderly population and its association with antinuclear antibodies.

The presence of anticardiolipin antibodies (aCL) has been associated with arterial and venous thrombotic events in connective tissue diseases. Previous investigations have suggested an increased incidence of aCL in the elderly population. We have studied the prevalence of aCL in large groups of 300 healthy elderly (mean age 70) and 543 younger subjects. aCL were determined by ELISA for the presence of IgG and IgM antibodies and was detected in 37 individuals (12%). This compared with an overall prevalence in a younger population of 2%. In addition, aCL was detected in 23% of elderly individuals who were also positive test for antinuclear antibodies (ANA). There was, however, no correlation with the presence of rheumatoid factor or lymphocytotoxic antibodies in this elderly group. Therefore, aCL have increased prevalence in an elderly population, and were associated with a positive test for ANA.

Adult↗

PubMed1988

Measles virus-induced suppression of lymphocyte proliferation.

The mechanism by which measles virus induces immunosuppression was investigated using an in vitro system employing phytohemagglutinin (PHA)-induced human peripheral mononuclear cell (PBMC) proliferation. At a multiplicity of infection of 1.0 or greater measles virus significantly inhibited (45%) the proliferation of PBMC. This inhibition was not due to an alteration in the kinetics of proliferation. PHA-stimulated PBMC were then infected with measles virus for 72 hr and irradiated (3200 rad) to prevent further proliferation. These infected, irradiated PBMC when added to fresh autologous PBMC caused significant inhibition of lymphoproliferation over a wide range of infected:fresh cell ratios (maximum inhibition seen at a 1:1 ratio, 85% inhibition). Virus recovered from the irradiated, infected cells was 100-fold lower than the virus titer needed to cause inhibition by direct addition of measles virus. However, antibody to measles virus reversed the inhibition. Virus-free supernatant fluids from the infected irradiated cells caused immunosuppression of the PHA response. This immunosuppressive material induced by the measles virus was maximally produced after 72 hr and did not appear to require viral replication. This factor was not prostaglandin E or interferon-alpha or -gamma. The production of such suppressive factors during viral infection may explain some of the profound immunosuppression seen in situations in which little or no infectious virus can be detected.

Animals↗

PubMed1987

Long-term treatment of rheumatoid arthritis comparing nabumetone with aspirin.

This report summarizes the results of a 17-investigator multicenter six-month randomized double-blind parallel group study. The safety and efficacy of nabumetone 1,000 mg taken at bedtime was compared with that of aspirin 900 mg four times daily in the treatment of adult patients with active class II or III classical or definite rheumatoid arthritis. Two hundred sixty-four patients were entered into the study. Two hundred fifty-seven (126 nabumetone and 131 aspirin) patients were evaluable for safety. Two hundred thirty-four (113 nabumetone and 121 aspirin) patients were evaluable for efficacy. There was significant improvement in each of six clinical measurements of efficacy in both treatment groups and little difference between groups. The somewhat greater improvement in articular index and duration of morning stiffness in the nabumetone-treated group did not reach statistical significance. There was an equal percentage of patient withdrawal for lack of efficacy in each group. Overall, the rate of patient withdrawal due to adverse experiences was greater (p = 0.01) for aspirin-treated patients. These experiences were usually dispepsia, abdominal pain, and tinnitus. It was concluded that nabumetone was an effective anti-inflammatory drug in the treatment of rheumatoid arthritis with less toxicity than aspirin.

Adolescent↗

PubMed1987

Interferons and systemic lupus erythematosus.

An array of data exists in patients with systemic lupus erythematosus which strong supports a role for interferon (IFN) in the disease process. The mechanism(s) which lead to an elevation of serum IFN in patients with SLE is unclear. IFN abnormalities may also contribute to a defect in natural killer function.

Antibody Formation↗

PubMed1987

[Inhibition of natural killer and interleukin 2-activated natural killer cell cytotoxicity by monosaccharides and lectins].

NK cell receptors may be saturated and inhibited by a serial monosaccharides and lectins. Subsequently, NK cytotoxicity diminished in different ratios. Phosphorylated mannose and galactose were the major inhibitors. Also, the most of the lectins have NK cell inhibitory capacity. Normal lymphocyte may be activated by IL-2 within 72 hours culture. Those activated lymphocytes exerts high cytotoxicity and wide recognition capacity for the tumor targets. Besides, their receptors are less sensitive for the sugar inhibition. Lectins, have strong inhibition capacity even the lymphocytes are activated by IL-2.

Cells, Cultured↗

PubMed1986

Reversible inhibition of lymphokine-activated killer cell activity by lipoxygenase-pathway inhibitors.

Natural killer (NK) cells and lymphokine-activated killer (LAK) cells are anomalous cytotoxic cells which are potentially important in host defense against cancer. Several studies have demonstrated that natural killer (NK) cell activity can be suppressed by chemical inhibitors of the lipoxygenase pathway through inhibition of the production of leukotriene B4 (LTB4). The present study investigated the effects of the lipoxygenase inhibitors BW755C and nordihydroguaiaretic acid (NDGA) on NK and LAK cell activity. NK cell function of fresh peripheral blood mononuclear cells (PBMC) was determined via a standard chromium release assay employing K562 as the tumor target. The LAK cell activity of PBMC which had been stimulated with 10 IU of interleukin-2 for 72 hr was determined against the NK-resistant cell line Daudi. Both BW755C and NDGA inhibited NK and LAK cell function at a variety of concentrations. Indomethacin, a prostaglandin synthesis inhibitor, did not bring about an appreciable diminution in NK or LAK cell activity. Inhibition of NK and LAK cell activities by BW755C and NDGA could be reversed by washing the effector cell suspensions prior to the cytotoxic assay or by adding LTB4 (10(-11)-10(-8) M) directly to the effector:target suspensions. These data indicate that certain arachidonic acid oxidation products of the lipoxygenase pathway are essential for the function of LAK cells.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗

PubMed1986

Inert particles inhibit natural killer cell function in vitro.

Aqueous suspensions of inert particles were found to inhibit the baseline and interferon-enhanced natural killer (NK) cell activity of peripheral blood mononuclear cells (PBMC) and large granular lymphocytes (LGLs). This inhibition was induced with latex, silica, and Sephadex particles. The suppression of NK activity was not related to effector cell death as determined by trypan blue exclusion. The inhibition of NK cell function was more pronounced with prolonged incubation and could be partially reversed with monocyte depletion or the addition of indomethacin, a prostaglandin synthesis inhibitor, but not with the addition of the lipoxygenase inhibitors nordihydroguaiaretic acid and BW755C. Similarly, particle exposure inhibited the NK cell function of monocyte-depleted large granular lymphocytes with and without the add-back of glass adherent cells, implying that monocyte-independent NK suppressive mechanisms were also present. These data demonstrate that inert particles are immunosuppressive in vitro and can inhibit baseline and interferon-stimulated NK cell function of LGLs and PBMC through monocyte-dependent and independent pathways.

Humans↗

PubMed1986

Cytotoxic mechanisms in vitro against Epstein-Barr virus infected lymphoblastoid cell lines in rheumatoid arthritis.

Impaired regulation of latent infection with Epstein-Barr virus (EBV) may contribute to the pathogenesis of rheumatoid arthritis (RA) by allowing uncontrolled polyclonal B cell activation. The control of EBV infection in vitro is dependent on several cytotoxic lymphoid cell populations. The present report examines the suppression of early lymphoblastoid outgrowth by natural killer (NK) like cells and the ability to form cytotoxic T lymphocytes (CTLs) specific for EBV in vitro. The latter was measured by a regression assay of EBV induced lymphoblastoid transformation. In this assay the regression of B cell outgrowth at four and six weeks is due to the generation of CTLs specific for EBV. Patients with RA were defective in this ability to generate CTLs. Eight out of nine patients with RA had a geometric mean at the 50% regression end point equal to or greater than 20 X 10(5) cells/ml. In contrast, the geometric mean for all control donors was less than 4 X 10(5) cell/ml. NK activity was measured by a conventional 51Cr release assay with K562 targets. Patients with RA did not have significantly different activity from that of controls (RA patients, n = 4, 45.6 +/- 19.7% (means +/- SD) at 50:1, effector:target; normals, n = 5, 56.6 +/- 5.7%). No spontaneous NK activity was detected against allogeneic or autologous EBV infected B cell targets. When peripheral mononuclear cells from patients were incubated for six days with interleukin-2, lysis of EBV infected targets was seen. No difference in this activity was seen between RA and control studies. Overall, these studies show that patients with RA are defective in their ability to generate CTLs specific for EBV in vitro.

Adult↗

PubMed1986

Serum factors which suppress natural cytotoxicity in cancer patients.

Spontaneous cytotoxicity mediated by natural killer (NK) cells is potentially an important mechanism of immunosurveillance against tumor or virus-infected cells. NK activity is impaired in many cancer patients. This study investigated the possibility that humoral factors are responsible for depressed NK activity in cancer patients and examined whether these factors were anti-lymphocyte antibodies (ALA) or immune complexes. The degree of NK suppression induced by 20 cancer patients' sera was determined by preincubating normal peripheral blood mononuclear cells with cancer sera. Eight of the 20 serum samples from cancer patients had NK-suppressive humoral factors. Elimination of immune aggregates by ultracentrifugation did not remove the inhibitory factors. The degree of NK suppression induced by cancer sera correlated with the extent of NK impairment in the serum donors (p less than 0.05). The cancer sera was examined for the presence of ALAs using flow cytometry. All cancer sera tested contained only low ALA reactivity to NK cell-enriched suspensions (less than 15%). This is in marked contrast to previous reports regarding NK-inhibitory systemic lupus erythematosus sera which contained large amounts of large granular lymphocyte (LGL) reactive ALAs. This study demonstrates that certain cancer sera suppress NK cell function. These inhibitory serum factors do not appear to be LGL-reactive ALAs or immune aggregates.

Adult↗

PubMed1985

Relationship between circulating interferon and anti-interferon antibodies and impaired natural killer cell activity in systemic lupus erythematosus.

Interferon (IFN) production and response are impaired in a high percentage of systemic lupus erythematosus (SLE) patients. In addition, elevated serum levels of alpha-IFN or anti-alpha-IFN antibodies are present in some SLE patients. This study examined the relationship of circulating IFN and anti-IFN antibodies to the impairment of natural killer (NK) cell function in SLE. All 15 SLE patients studied had measurable circulating alpha-IFN, while the normal controls had minimal serum IFN. Neither patient nor control sera contained any detectable anti-alpha-IFN activity. However, most of the SLE patients demonstrated defects in NK cell function. Because these defects in NK cell function appeared to be associated with circulating IFN, but not anti-IFN, antibodies, the effect of prolonged in vitro IFN exposure on NK cell function of peripheral blood mononuclear cells was determined. It was found that prolonged exposure to IFN induced both an apparent defect in IFN response and a definite impairment of baseline NK cell function. These results suggest that prolonged elevation of circulating alpha-IFN levels could be responsible, in part, for the defects in natural cytotoxicity present in SLE.

Autoantibodies↗

PubMed1985

Generation of natural killer cells and lymphokine-activated killer cells in human AB serum or fetal bovine serum.

Interleukin 2 (IL-2) can induce or enhance the cytotoxic activity of natural killer (NK) cells and lymphokine-activated killer (LAK) cells. The effects of fetal bovine serum (FBS) and human AB serum (HABS) on the IL-2-induced NK cell and LAK cell activities of large granular lymphocytes (LGL) were measured, respectively, against the NK-sensitive cell line K562 and the LAK-sensitive cell line Daudi. FBS and HABS were essentially equivalent in their effects on IL-2-dependent NK activity with prolonged culture. However, with prolonged incubation from 1 to 5 days of PBMC in the presence of IL-2, there was considerably less generation of LAK cell activity in FBS (Day 3: 5.3 +/- 3.4 LU/10(7) cells) compared to HABS (Day 3: 44.6 +/- 4.2 LU/10(7) cells) (P less than 0.05). These differences in IL-2-dependent LAK cell generation did not appear to be due to the lot of the FBS or to activating factors present in individual samples of HABS. Similarly, the suppressive effects of FBS could not be reversed with increasing concentrations of IL-2 ranging from 10 to 100 U/ml. Importantly, the presence of FBS in the cultures resulted in more cell death (15.9 +/- 5.6%) at 4 days of culture compared to HABS (1.8 +/- 1.0%) (P less than 0.05). These results suggest that FBS may inhibit generation of LAK effector cells, but not NK cells in cultures containing IL-2 and that the use of HABS as a culture supplement is preferable to FBS in studies of human LAK cell function.

Animals↗