Effect of Fc-Receptor Modulation on Mumps-Virus-dependent Lymphocyte-mediated Cytotoxicity in Vitro

The natural cytotoxicity of peripheral blood lymphocytes (PBL) from normal human donors to a variety of tissue culture target cells increases upon brief exposure of lymphocytes to mumps virus. The effector cells operative in this system have Fc receptors for IgG (FcR), since cytotoxicity was abolished when FcR ⁺ cells were removed by passage of the lymphocytes over immune-complex columns. When PBL were treated with immune complexes for 16 h at 37°C, their FcR activity was sharply decreased (modulation), as indicated by a significantly reduced capacity of the treated cells to display antibody-dependent cytotoxicity (ADCC). Modulation had variable effects on natural cytotoxicity. In contrast, the virus-dependent cytotoxicity above the natural cytotoxicity remained essentially unchanged, indicating that a functionally intact FcR is not required in this system for carrying out cytolysis.     

The Role of Viral Glycoproteins in Mumps-Virus-dependent Lymphocyte-mediated Cytotoxicity in Vitro

Human peripheral blood lymphocytes (PBL) from healthy donors express enhanced natural cytotoxicity to target cells after a brief exposure 10 mumps virus in vitro, We describe here experiments aiming at elucidating the mechanism of this virus-dependant cytotoxicity. Treatment with proteolytic enzymes resulted in virus particles depleted of one or both kinds of their glycoprotein spikes. Removal of both of these components from the virion abrogated their ability to enhance cytotoxicity. This virus-dependent cytotoxicity was significantly but not completed reduced when one of the spike glycoproteins (gp 75, HANA) was removed selectively. Similarly, nucleic-acid-free preparations of the spikes, obtained by detergent treatment of mumps virions, also dialed enhanced cytotoxicity. However, the activity of these preparations was lower than that of untreated virions Further evidence for the importance of II AN A was provided by the use of F(ab')₂ fragments of anti-HANA-specific rabbit antibodies. When these fragments were allowed to react with virus before addition of the virus to PBL. no augmentation of cytolysis was observed. Antibody fragments specific for the other spike protein (gp 61, F) failed to inhibit the virus-dependent enhancement of PBL-mediated cytotoxicity. However, anti-HANA and anti-F blocked this reaction when added directly to the mixture of virus-treated PBL and target cells. The results are compatible with the hypothesis that virus-dependent cytotoxicity requires HANA for anchoring the virus to PBL receptors (and perhaps to bring effector and target cells into closer contact), whereas F may be involved in subsequent events increasing effector cell function.     

The Role of Viral Glycoproteins in Mumps Virus-Mediated Antibody-Dependent Cellular Cytotoxity in Vitro

Treatment of human peripheral blood lymphocytes with live or UV-inactivated mumps virions enhances antibody-mediated cellular cytotoxicity (ADCC), reflected by increased target cell lysis in a 51Cr-release assay or an increased number of plaque-forming cells on monolayers of bovine erythrocytes (Eb) in the presence of anti-Eb antibodies. Virus treatment of the Eb targets causes a similar enhancement. The role of viral glycoproteins in ADCC enhancement was investigated by using a panel of monoclonal antibodies raised in mice against mumps virions. Most of the lymphocytes bound mumps virions, as ascertained by indirect immunofluorescence. A high proportion of virus-treated lymphocytes also formed rosettes with Eb. Anti-HN antibodies inhibited rosetting to various degrees. Although antibodies with high haemagglutination inhibition titres were most efficient inhibitors, antibodies without this serological activity were also inhibitory. Anti-F antibodies were only weakly inhibitory, and anti-NP antibodies had no effect. Anti-HN antibodies also abrogated target cell lysis in the 51Cr-release assay and effector cell recruitment in the ADCC plaque assay by inhibiting virus-mediated Eb-lymphocyte interactions both at the target cell and at the effector cell level. Anti-F or anti-NP antibodies were only weakly or not at all inhibitory. The results suggest that virus-mediated enhancement of ADCC is caused by the HN glycoprotein, primarily (although perhaps not exclusively) by its improvement of the effector cell-target cell contacts necessary for the efficient execution of target cell lysis.     

Postjunctional α1- and α2-adrenoceptors mediating contraction in isolated human groin arteries and veins

By means of selective agonists and antagonists for α₁- and α₂-receptors, the α-receptor subtypes in human groin arteries and veins were characterized and compared. In the arteries the α₁-receptor blocker prazosin caused a concentration-dependent parallel displacement of the noradrenaline (NA) concentration-response (cr) curve without reduction of maximum (pA₂=9.86); the selective α₂-receptor antagonist rauwolscine in the concentration 10^-8 M caused a right-ward shift of the NA cr-curve without reduction of E_max, but 10^-7 M and 10^-6 M caused little or no further shift. In the veins, the two antagonists had the opposite effects. Rauwolscine caused a concentration-dependent right-ward shift of the NA cr-curve without depression of maximum (pA₂=9.03); prazosin 10^-9 M significantly displaced the NA cr-curve, whereas 10^-8 M and 10^-7 M caused little or no further shift. The responses to the α₂-receptor agonist clonidine in the arteries were too small to allow calculations of pEC50 values; in the veins contractions were elicited in all vessel segments investigated (pEC₅₀=6.24). Phenylephrine, selective for α₁-receptors, was significantly more potent in arteries than in veins. NA was significantly more potent in veins than in arteries. It is concluded that in human groin vessels, there is a functional predominance of arreceptors in the arteries and of a2-receptors in the veins.     

Effects of nimodipine,Bay K 8644 and pinacidil on α1- and α2-adrenoceptor-mediated vasoconstriction in human hand veins

The effects of nimodipine, Bay K 8644 and pinacidil, three drugs interfering with transmembrane Ca²⁺ fluxes in different ways, were investigated in isolated human hand veins. Their ability to influence the concentration-response relationship for noradrenaline (NA) was assessed in the absence and presence of prazosin or rauwolscine. The contractile response to NA was almost abolished in Ca²⁺-free medium. Nimodipine and pinacidil depressed the NA concentration-response curve both in the absence and presence of α-adrenoceptor blockers. The NA response was only partially inhibited by nimodipine, indicating that NA may activate nimodipine-insensitive influx pathways, presumably receptor-operated calcium channels. Pinacidil inhibited the contractile response to 124 mM K⁺ and reduced the NA-induced contraction in the presence of nimodipine, suggesting that pinacidil has actions other than the opening of potassium channels and subsequent membrane hyperpolarization. Bay K 8644 increased the NA potency fourfold in the presence of rauwolscine, whereas it had no effect on the NA response in the presence of prazosin and in the absence of α-adrenoceptor blockade. Such an action of Bay K 8644 can be reconciled with α-adrenoceptor activation causing membrane depolarization and opening of potential-operated calcium channels. It may be concluded that both α₁- and α₂-adrenoceptor-mediated contractions in human hand veins are highly dependent on Ca²⁺ influx, although the mechanisms utilized to bring about this influx partly differ between the two receptor subtypes.     

Regulation of Growth and Differentiating of Pre-Activated B Lymphocytes

The differential effects of H-2 IAk-specific T helper cells, their soluble factors and Sepharose-coupled anti-mu antibodies on the growth and differentiation of pre-activated B cells were studied. It was found that the prolonged growth of pre-activated B cells required activation signals from major histocompatibility complex (MHC)-restricted T helper cells or Sepharose-coupled anti-mu antibodies. The MHC-restricted T helper cells induced both prolonged growth and differentiation of activated B cells. Anti-mu antibodies together with T helper cell-derived soluble factors induced prolonged growth of activated B cells, but no differentiation into Ig secretion was detected. The inhibition of Ig secretion in anti-mu cultures could be overcome to some extent by either MHC-restricted T helper cells or lipopolysaccharide together with soluble factors. It was also observed that T helper cell interactions were needed for long-term in vitro culture of pre-activated B lymphocytes.     

Endothelin-induced contractions in placental arteries is mediated by both ETA- and ETB-receptors

We have examined the contractile response to the vasoconstrictor endothelin-1 (ET-1) in uteroplacental arteries from normal pregnant women in the presence and absence of specific ET-receptor antagonists and agonists, and the vasodilator nitric oxide. Segments of placental arteries (n = 97) obtained from 37 placentas immediately after delivery were mounted in organ baths superfused with Krebs-Ringer solution at 37 °C. The tension was recorded isometrically and registered on a polygraph. We found that the placental artery segments responded to ET with a dose-dependent vasoconstriction. Half-maximal response was obtained at 2.6 × 10^?8 M . At 10^?7 M , the contractile response was 52% of the maximum KCl-response. The ET-1 induced contraction at 10^?7 M was inhibited by 74% after addition of the ET_A -antagonist BQ-123 (10^?6 M ), and by 58% by the ET_B -antagonist BQ-788 (10^?6 M ). Both BQ-123 and BQ-788 almost completely abolished the response to ET (10^?7 M ). The selective ET_B -agonist IRL-1620 also elicited vasoconstriction in the placental artery with a half maximal response at 8 × 10^?7 M . On a molar basis at 10^?7 M , the contraction by IRL-1620 as compared to ET was 30-fold lower. The contractile response of IRL-1620 (10^?6 M ) was inhibited by 99% by BQ-788 (10^?6 M ). After pre-contraction of the placental arteries with ET-1 (10^?7 M ), the vessels relaxed in response to the nitric oxide donor, nitroglycerin (10^?6 M ). The present results show that ET-1 contracts placental arteries through both ET_A- and ET_B-receptor activation. Nitric oxide (10^?6 M ) was able to relax more than half of the initial ET-1 contraction, indicating that nitric oxide may be an important vasodilator in the placenta.     

Nicotine-induced increases of noradrenaline turnover in discrete noradrenaline nerve terminal systems of the hypothalamus and the median eminence of the rat and their relationship to changes in the secretion of adenohypophyseal hormones

The effects of acute single doses (0.3 and 1 mg/kg) of nicotine on various hypothalamic catecholamine nerve terminal systems and on the secretion of adenohypophyseal hormones in the rat were studied. Nicotine, in a dose of 1.0 mg/kg, increased noradrenaline turnover in the median eminence and in the peri- and paraventricular hypothalamic regions. The dopamine and noradrenaline nerve terminal systems in the median eminence and the dorsomedial hypothalamic nucleus respectively were unaffected. Serum GH levels were decreased and serum prolactin levels increased after a dose of 1 mg/kg. In the presence of tyrosine hydroxylase inhibition, nicotine in a dose of 1 mg/kg, instead increased GH and also LH secretion. It is suggested that the preferential increases of noradrenaline turnover in various hypothalamic noradrenaline nerve terminal systems by nicotine may be partly responsible for the nicotine induced increases of serum prolactin, GH and LH levels observed.