Enhancement Of Natural Killer Activity Research Articles

Interleukin 2 enhances natural killer cell activity through induction of gamma interferon.

Highly purified interleukin 2 (IL 2), free of interferon activity, enhanced natural killer (NK) cell activity against tumor cells in mouse spleen cell cultures and in human peripheral lymphocyte cultures in a manner similar to that of interferon (IFN). We determined that IL 2 enhanced NK activity indirectly in a cascade manner by the induction of gamma IFN (IFN-gamma) in the cultures, which actually mediated the enhanced killing. Accordingly, lymphocyte cultures treated with IL 2 alone produced 10 to 100 U of IFN per ml in 6 to 24 h of culture. The IFN was typed as IFN-gamma by specific antibodies. Specific antibodies either to natural IFN-gamma or to a synthetic peptide corresponding to the human IFN-gamma N-terminal amino acids, when added to cultures treated with IL 2, completely blocked IL 2 enhancement of NK cell activity for both the mouse and human systems. IL 2-induced proliferation was not affected by the antibodies. Thus, the enhancement of NK cell activity by IL 2 is completely mediated by IL 2-induced IFN-gamma. The findings clearly indicate a cascade effect whereby one lymphokine (IL 2) induces the production of another. The latter lymphokine (IFN-gamma) then mediates an important biological effect (natural killing).

Enhancement of natural killer cell activity and 2-5A synthetase in mice treated with polyadenylic · polyuridylic acid

Previous studies have demonstrated that splenic natural killer (NK) cell activity of mice can be efficiently enhanced by polyadenylic · polyuridylic acid [poly(A) · poly(U)]. Moreover, inoculation of mice with the duplex leads to the production of interferon (IFN). The NK boosting effect in mice was analyzed in parallel with the assay of an enzyme marker for the production and action of IFN, pppA(2′p5′A)n synthetase (2-5A synthetase). Kinetic studies revealed that splenic mononuclear cells of C3H/He mice inoculated intravenously with 10 μg or more of poly(A) · poly(U) showed significantly enhanced cytotoxic activity in an in vitro 51Cr-release assay using NK sensitive YAC-1 target cells. Intravenous, intraperitoneal, and intramuscular administration of the duplex into mice were equally effective in obtaining such NK boosting effect. Furthermore, repeated weekly injections of poly (A) · poly(U) did not induce resistance against NK boosting in the organisms. The levels of 2-5A synthetase in the organs, particularly spleens, of mice inoculated similarly with poly(A) · poly(U) were greatly increased with a dose-dependent pattern. Repeated injections of mice with the duplex at 4-day intervals resulted also in significantly enhanced levels of splenic 2-5A synthetase after each injection. Thus, as a whole, enhanced NK activity accompanied increased levels of 2-5A synthetase in mice treated with poly(A) · poly(U).

Activity of Natural Killer Cells in Normal Pregnancy and Edema-Proteinuria-Hypertension Gestosis

Natural killer cytotoxicity of peripheral blood lymphocytes in normal pregnancy and edema-proteinuria-hypertension (EPH) gestosis was investigated and compared to natural killer cytotoxicity in lymphocytes of normal nonpregnant control donors. These lymphocytes were also compared for their ability to respond to interferon treatment in vitro. Natural killer activity was found to be only slightly decreased in normal pregnant women but was found to be increased in patients with EPH gestosis. Interferon treatment of peripheral lymphocytes caused strong enhancement of natural killer activity in lymphocytes of normal pregnant women but resulted in only weak activities in lymphocytes from patients with EPH gestosis. We consequently concluded that pre-natural killer lymphocyte subpopulations from patients with EPH gestosis have already been activated by a presently still unknown stimulator.

Enhancement of natural cytotoxicity by beta-endorphin.

The role of enkephalins, beta-endorphin, or other neuropeptides produced by the nervous system in the alteration of immune responsiveness is generally unknown. The present studies were undertaken to investigate the role of these neuropeptides in the modulation of human spontaneous cytotoxicity induced by natural killer (NK) cells. Natural cytotoxicity was measured by using a standard 51Cr release assay with radiolabeled K562 cells. NK activity was significantly enhanced by both beta-endorphin (30.5 +/- 11.5%, M +/- SE, relative enhancement at 50:1, effector:target (E:T) ratio, 10(-14)M beta-endorphin) and methionine-enkephalin (met-enkephalin) (27.4 +/- 9.7% relative enhancement at 10(-9)M). The magnitude of relative enhancement significantly correlated with increasing concentrations of beta-endorphin. Leucine-enkephalin, alpha-endorphin, and morphine did not augment NK activity. The enhancement of NK activity with beta-endorphin increased at all E:T ratios tested. Naloxone inhibited the augmentation of NK activity produced by beta-endorphin and met-enkephalin. By using a combination of a standard 51Cr release and soft agarose single cell analysis assays, beta-endorphin increased both the number of E:T cell conjugates and the number of active killer cells among target-binding cells. The maximal effector cell recycling capacity was increased by 170%. These studies provide new insight into the mechanisms by which neuropeptides produced by the nervous system can alter immune responsiveness.

Activity of natural killer cells in normal pregnancy and edema-proteinuria-hypertension gestosis

Natural killer cytotoxicity of peripheral blood lymphocytes in normal pregnancy and edema-proteinuria-hypertension (EPH) gestosis was investigated and compared to natural killer cytotoxicity in lymphocytes of normal nonpregnant control donors. These lymphocytes were also compared for their ability to respond to interferon treatment in vitro. Natural killer activity was found to be only slightly decreased in normal pregnant women but was found to be increased in patients with EPH gestosis. Interferon treatment of peripheral lymphocytes caused strong enhancement of natural killer activity in lymphocytes of normal pregnant women but resulted in only weak activities in lymphocytes from patients with EPH gestosis. We consequently concluded that pre-natural killer lymphocyte subpopulations from patients with EPH gestosis have already been activated by a presently still unknown stimulator.

Interferon and natural killer activity in multiple myeloma. Lack of correlation between interferon-induced enhancement of natural killer activity and clinical response to human interferon-alpha.

Natural killer (NK) activity of peripheral lymphocytes was measured in 39 patients with multiple myeloma prior to and during interferon (IFN) therapy. NK activity increased in a majority of patients following the first injection of IFN and remained at an increased level during 1 year of therapy. Lower doses of IFN seemed to induce a greater increase in NK activity than higher doses. No correlations could be observed between the response of the tumors to IFN therapy and pretreatment levels of NK activity, IFN-induced enhancement of NK activity in vitro or IFN-induced enhancement of NK activity in vivo.

Natural killer cells induced by acute and chronic toxoplasma infection

The recent interest in natural killer (NK) cells in immunosurveillance and the ability of infection with certain organisms to modulate NK activity led us to examine the influence of Toxoplasma gondii infection on mouse NK cells. Infection of BALB/c mice with 5 × 10 3 virulent Toxoplasma intraperitoneally (ip) resulted in significantly enhanced NK activity in peritoneal exudate cells (PC) and in spleen cells (SC). Intravenous (iv) and subcutaneous (sc) challenge of BALB/c mice with Toxoplasma also resulted in enhanced natural killer (NK) activity in PC and SC. In BALB/c mice, as well as in other strains (A/J, C57BL/6, C3H/HeJ, CeH/HeN, [A/J × C3H]F 1), peak augmentation of PC and SC NK activity was observed 3 days following ip Toxoplasma challenge. Administration of silica to mice abolished Toxoplasma-induced NK cytotoxicity. BALB/c mice chronically infected with Toxoplasma had significantly higher endogenous NK activity than did controls in PC but not in SC. Chronically infected BALB/c mice boosted with virulent Toxoplasma ip exhibited significantly enhanced NK activity in PC but not in SC. Thus, acute and chronic infection with Toxoplasma modulates NK activity in addition to macrophage activation and thereby provides a system that should facilitate study of the relative contribution of NK cells and activated macrophages in resistance to tumor growth and spread.

Spleen cells release thiols extracellularly as an antioxidant defense mechanism

The biological response modifier OK-432 (Picibanil) (manufactured in Japan) is produced by lyophilization of cultures of the low virulent Su strain of group A Streptococcus pyogenes of human origin. This preparation has been shown to have multiple effects on the immune system and has been used as an anti-cancer therapeutic agent in man. It has been shown that OK-432 augments the cytotoxic activity of human natural killer (NK) cells. We have proposed that natural killer cytotoxic factors (NKCF) derived from NK cells play a role in the mechanism of NK cell-mediated cytotoxicity (CMC). The present study investigates the underlying mechanism of the OK-432-mediated enhancement of NK activity by determining whether OK-432 has an effect on the induction and activity of NKCF produced by NK cells. Treatment of peripheral blood lymphocytes (PBL) with OK-432 for 20 hr and wash resulted in significant augmentation of NK CMC and this enhancement was dependent on the concentration of OK-432 used. Coculture of the OK-432-treated PBL with U937 resulted in a several-fold enhanced production of NKCF in the supernatant. The NKCF produced were similar to those produced by untreated effector cells in that they had the same NK target specificity for lysis. The time kinetics of stimulation of PBL with OK-432 for optimal production of NKCF was found to be 8–12 hr. It was also observed that culture of OK-432-treated PBL in the absence of stimulator cells spontaneously release significant amounts of NKCF into the supernatant. The supernatant containing NKCF was tested for interleukin 2 (IL-2) activity using an IL-2-dependent HT-2 line. It was found that there was no direct correlation between the levels of NKCF and IL-2 activity. The results of this study demonstrate that OK-432 stimulates NK cells to produce NKCF in the presence or absence of stimulator cells. The optimum concentration of OK-432-induced augmentation of NK CMC paralleled that seen for optimum NKCF production, suggesting that one mode of action of OK432 is to enhance NKCF production in a manner reminiscent of IFN and IL-2. The results also point out that OK-432 acts by a mechanism independent of the action of IL-2.

Interferon induction and augmentation of natural-killer activity by Staphylococcus protein A

Protein A from Staphylococcus aureus (SpA)-induced interferon (IF) production and augmented natural-killer (NK) activity in human peripheral blood mononuclear cells (PBL). IF production was apparent 8 hr and peaked 24 hr after exposure to SpA. Augmentation of NK activity occurred within 10 hr of IF production with peak NK activity occurring 48 hr after exposure to SpA. SpA-induced augmentation of NK activity correlated directly with IF production ( r = 0.997; P < 0.005). Supernatants from SpA-induced PBL cultures also enhanced NK activity. Pretreatment of these supernatants with antileukocyte (Type I) IF serum had no effect on either their ability to augment NK activity or their antiviral (IF) activity. Both the NK-augmenting and antiviral activity of such supernatants were abrogated by trypsin digestion, heat inactivation (56 °C for 1 hr) and treatment at pH 2 for 48 hr, suggesting that Type II IF was induced by SpA. Furthermore, the kinetics of development of antiviral activity in human fibroblast cultures by SpA-induced IF followed the pattern characteristic of Type II IF. Cell-fractionation studies showed that SpA-induced IF production was depressed in macrophage-enriched PBL and increased in nonadherent PBL. Moreover, depletion of Fcreceptor-positive (FcR+) lymphocytes with IgG-coated bovine erythrocytes before SpA treatment abrogated IF production and augmentation of NK activity. Taken together, these data suggest that SpA induces human nonadherent, FcR+ PBL to produce Type II IF, which augments NK activity against several cultured target cell lines.

Augmentation of cytotoxicity by splenic cells of pregnant or human chorionic gonadotropin-treated normal mice.

The natural killer (NK) activity, of an allogeneic tumor system, was found to be enhanced by the total splenic population of either pregnant or normal female BALB/c mice treated with human chorionic gonadotropin (HCG). The splenic population of the early pregnant (9-10 days) mice resulted in a statistically significant increase in NK activity over nonpregnant controls at all effector/target ratios tested. The mid (12-13 days) and the late (15-16 days) pregnant groups also significantly enhanced NK activity above control values at effector/target ratios of 100:1, 50:1 and 25:1. The i.v. administration of carrageenan into pregnant mice abolished the increased NK activity suggesting a putative role for the macrophage in this system. HCG administered to normal female BALB/c mice resulted in enhanced NK activity similar to that seen for the pregnant mice. This augmented NK activity does not appear to be effected by either the number or the timing of HCG administration. The augmentation of NK activity of HCG treated mice was also detected in a syngeneic system utilizing 51Cr labeled M109 tumor target cells and BALB/c effector cells.