Natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities can be differentiated by their different sensitivities to interferon and prostaglandin E1

Alteration of NK- and ADCC-activities in rats genetically selected for low or high platelet serotonin level

By selective breeding we have recently obtained two discrete sublines of rats that differ in serotonin content in their platelets. As both serotonin and platelets may influence, or even take part, in immune reactions, we tested in this work the natural cytotoxicity in rats with constitutionally different platelet serotonin levels (PSL). Rats with low platelet serotonin level (mean +/- SD, 1.26 +/- 0.14 micrograms 5HT/mg protein; 81% vs. controls) had significantly higher (P less than 0.001) natural killer (NK) activity (mean +/- SD, 9.1 +/- 3.9%) than control rats with average PSL (1.57 +/- 0.18 micrograms 5HT/mg protein). On the contrary, rats with constitutionally high PSL (2.42 +/- 0.21 micrograms 5HT/mg protein, 154% vs. controls) had somewhat lower (P less than 0.02) NK activity (4.1 +/- 1.7%) than control animals (5.7 +/- 1.9%). Antibody-dependent cellular cytotoxicity (ADCC) against nucleated targets of the RCH line, detecting lymphoid effectors, as well as ADCC against chicken red blood cells (CRBC), detecting predominantly non-lymphoid effectors, were also significantly higher (P less than 0.001) in rats with low PSL (19.6 +/- 6.8% vs. 6.6 +/- 3.1% in controls for lymphoid effectors, and 71.8 +/- 6.1% vs. 48.7 +/- 8.8% in control rats for non-lymphoid effectors). However, no significant alteration of either ADCC was determined in rats with high PSL. The results suggest in vivo regulation of natural cytotoxicity by serotonin.

In vivo bidirectional regulation of mouse natural killer (NK) cell cytotoxic activities by Leu-enkephalin: reversibility by naloxone

Intraperitoneal injection of Leu-enkephalin (LENK, 10 or 7.5 mg/kg) induced bidirectional modulation of natural cytotoxic activities in spleens of CBA mice (suppression followed by enhancement). NK-cytotoxic activity was more affected than the ADCC. Early suppression of NK activity could be reversed by 4 x M excess of naloxone injected 20 min before LENK, suggesting that the suppression was mediated by opioid receptors. Subsequent increase of NK activity could not be abrogated by naloxone, at least not completely. Naloxone itself decreased NK activity 12 hours after treatment, but enhanced ADCC at 24 and 48 hours. This increase was abrogated by LENK. In addition to functional alterations, LENK also induced phenotypic changes of spleen cells, i.e. a decrease in the percentage of asialo-GM-1+ cells 24 hours posttreatment. There was no correlation between LENK-induced alterations of cytotoxic function and the percentage of cells with NK phenotype (GM-1+). Thus, LENK modulates cytolytic functions and the phenotype of NK cells in vivo in a complex way, which besides opioid mechanisms may also include non-opioid ones.

Augmentation of monocyte-mediated antibody-dependent cellular cytotoxicity by protein synthesis inhibitors: evidence for an endogenous regulatory mechanism

Protein synthesis inhibitors, cycloheximide and puromycin, were used in cytotoxic assays employing human peripheral blood monocytes as effectors and sheep erythrocytes as target cells. ADCC could be initiated and could also achieve its full lytic activity in the absence of new protein synthesis. Furthermore, an augmentation of ADCC was observed in the presence of protein synthesis inhibitors. This augmentation was due to an increase in the cytotoxic ability of effector cells rather than a change in the lytic susceptibility of the target. Enhanced cytotoxic potential could not be attributed to an increase in the expression of FcRI but could be due to increased availability of antibody for mediating ADCC as a result of reduced numbers of FcRII. Suppression of prostaglandin-E2 release by monocytes was noted in the presence of cycloheximide, possibly as a result of inhibition of synthesis of cyclooxygenase. However, prostaglandin-E2 and other arachidonic acid metabolites did not appear likely to play a role in negatively regulating human monocyte ADCC since neither cytotoxicity nor cycloheximide-induced augmentation was affected by the presence of exogenous prostaglandin-E2 or arachidonic acid. Cycloheximide was found to induce the secretion of superoxide anions by monocytes, but a role for reactive oxygen species in cycloheximide-induced augmentation of ADCC could not be established by experiments involving the use of catalase or superoxide dismutase. These results raise the possibility that a rapidly turning over protein which negatively regulates monocyte-mediated ADCC exists.

Splenic natural cytotoxic activity is enhanced during growth of a murine fibrosarcoma

We have shown previously that the natural killer (NK) cell activity of DBA/2J mice bearing M-1 fibrosarcomas is consistently depressed at the later stages of tumor growth. The apparent mechanisms of inhibition are suppressor cell activation and prostaglandin E (PGE) production by tumor and lymphoid cells. In contrast, we show here that the natural cytotoxic (NC) activity of cells from the spleen, blood, and lymph nodes of mice bearing M-1 tumors is enhanced when compared to that of age- and sex-matched control mice. This enhanced NC activity does not appear to be due to increased cytolytic activity of macrophages but, rather, to enhanced cytolytic activity of multiple populations of non-adherent cells including B and T cells. Correlated with this is the finding that the NC activity of normal spleen cells is not inhibited in vitro by either PGE1 or PGE2 at levels which are inhibitory to NK cells. NC activity, although independent of PGE, is in fact enhanced by PGE1 in a dose-related fashion. These data indicate that NK and NC cells are regulated differently by PGE and during tumor growth. Utilizing a Winn assay, we also demonstrate that a cloned cell line with NC activity is capable of slowing tumor growth in vivo and that this action is improved if mice are treated with indomethacin concomitantly.

Pathogenesis of Treponema hyodysenteriae: induction of interleukin-1 and tumor necrosis factor by a treponemal butanol/water extract (endotoxin)

Biological activities of lipopolysaccharide-like (LPS-like, phenol/water extract) and endotoxin-like (butanol/water extract) preparations from Trepomena hyodysenteriae were examined. The treponemal phenol/water and butanol/water extracts were less toxic than E. coli LPS for murine peritoneal exudate cells (PECs). The treponemal phenol/water extract did not stimulate the production of interleukin-1 (IL-1) or tumor necrosis factor (TNF) from murine PECs. The treponemal butanol/water extract did induce production of IL-1 and TNF but at doses 5- to 50-fold higher than E. coli LPS. Natural killer cell activity was augmented by the treponemal butanol/water extract but not by the phenol/water extract. Suppression of a splenic anti-SRBC plaque forming cell response was observed when the LPS-like and endotoxin-like preparations from T. hyodysenteriae were administered 24 h prior to injection of the SRBC. These findings indicate that the butanol/water extracted material from T. hyodysenteriae is more biologically active than the phenol/water extracted material and that the treponemal endotoxin may contribute to the inflammatory response of swine dysentery by inducing IL-1 and TNF production.

In vivo and in vitro modulation of NK and ADCC activities of mouse spleen cells by peptidoglycan monomer (PGM)

The ability of peptidoglycan monomer (PGM), an immunomodulator obtained from Brevibacterium divaricatum, to modulate NK and ADCC activities of spleen cells was tested in mice with constitutively weak (C57B1) or strong NK activity (CBA, C3H). In weak reactors, i.v. injection of PGM enhanced the NK and ADCC activity as effectively as a known stimulator, poly I.C, and the dynamics of the response was comparable. In strong reactors, PGM caused two peaks of the ADCC response, and one peak of NK stimulation (after an initial decline), whereas poly I.C caused more or less persistent stimulation of both activities. Incubation of spleen cells with PGM was generally less effective than the treatment in vivo. No alteration of NK activity was recorded at high effector-to-target ratio (E:T), and at low ones, PGM caused suppression. This was true both for weakly and strongly reactive cells. ADCC was either unchanged (CBA spleen cells), stimulated (C3H), or suppressed at high E:T and enhanced at low E:T (C57B1). PGM apparently activates an interlocked regulatory mechanism, and the final outcome probably depends on relative concentrations of regulatory and effector cells and on their per cell activities. Hence the effect varied with the time interval between treatment and assay, with strain-related constitutive reactivity, and with the E:T ratio.

The mechanism of the inhibitory effect of progesterone on lymphocyte cytotoxicity: II. Relationship between cytotoxicity and the cyclooxygenase pathway of arachidonic acid metabolism

In the previous paper we have demonstrated that progesterone-treated lymphocytes of healthy pregnant women produce a 34,000 MW protein that inhibits cytotoxic activity and prostaglandin F2 alpha synthesis. Since recently it has been shown that certain leukotrienes have a stimulatory effect on natural killer activity, in this study an attempt was made to determine whether there is a relationship between cytotoxicity and PGF2 alpha synthesis or if alterations in the values of these parameters are independent. Arachidonic acid increased cytotoxic activity of healthy pregnant women's peripheral blood mononuclear cells (PBMC) in a concentration-dependent manner. Exogenous arachidonic acid was able to counteract the blocking effect of the above-mentioned protein produced by progesterone-treated lymphocytes. To determine whether the products of the cyclooxygenase or the lipoxygenase pathway of arachidonic acid metabolism are responsible for increased cytotoxicity, both enzyme systems were blocked separately. Both indomethacin and the lipoxygenase inhibitor BW 755C reduced cytotoxicity in a dose-dependent fashion. However, the lipoxygenase inhibitor prevented prostaglandin synthesis to the same extent, or even more than indomethacin, in all concentrations used; so, its blocking effect cannot be considered as supportive evidence for the role of leukotrienes in cytotoxicity. On the other hand, lipopolysaccharide, with a selective stimulatory effect on prostaglandin synthesis, increased cytotoxicity. Lipopolysaccharide had no effect on progesterone-pretreated PBMC. The above data allow the assumption that besides leukotrienes, cyclooxygenase products may also increase cytotoxicity.

Ameliorating effect of IFN-beta and anti-IFN-beta on coxsackievirus B3-induced myocarditis in mice

A significant reduction in the number of virus-induced myocardial lesions was effected by administration of murine interferon beta (IFN-beta) or polyriboinosinic: polyribocytidylic acid copolymer (pI:pC) at -24, 0, or 24 h but not 72 h postinoculation (p.i.) of coxsackie-virus B3 (CVB3) to adolescent CD-1 mice. Inoculation of interferon at any of the four times did not reduce virus titers in heart tissues at three or seven days p.i., but inoculation of pI:pC at -24, 0, or 24 h p.i. significantly reduced virus titers. Administration of anti-murine IFN-beta at 72 h p.i. significantly reduced myocarditic lesion numbers. The results suggest that there are two identifiable times after CVB3 inoculation in which interferon may play a role in CVB3-induced myocarditis: a very early time (+/- 24 h of virus entry) in which the presence of interferon is beneficial to the animal and a later time (72 h p.i. of virus) in which absence of interferon is beneficial to the animal. In vitro studies on the effects of IFN-beta or anti-IFN-beta antiserum on replication of CVB3 in permissive primary cultures of murine neonatal skin fibroblasts show that this virus is sensitive to the antiviral action of interferon which is produced in infected cultures.

Mechanisms of depression of splenic natural killer cell function in C57BL/6 mice infected with Leishmania donovani

C57BL/6 mice chronically infected with the protozoan parasite Leishmania donovani exhibit profoundly depressed splenic natural killer (NK) cell activity as measured by in vitro cytolysis of lymphoma target cells. Injection of infected mice with an interferon (IFN) inducer or in vitro treatment of infected splenocytes with IFN, a phorbol ester, or indomethacin failed to restore their NK activity to the degree shown by age-matched, uninfected mice. Fractionation of infected splenocytes by nylon wool, Sephadex G-10, or carbonyl iron and magnetism treatments was also unable to effect an increase in NK activity. Addition of infected splenocytes to uninfected ones in in vitro NK assays suppressed the NK activity of the latter, and the suppression could be partially or wholly abrogated by prior fractionation of infected splenocytes by the methods noted above. In vitro treatment of infected splenocytes with concanavalin A revealed the presence of NK activity in these cell populations. The results indicate that splenocytes in L. donovani-infected mice become insensitive to IFN stimulation; and the impairment of another, possibly IFN-independent pathway of NK-cell activation may also contribute to the observed L. donovani-induced depression in splenic NK activity in C57BL/6 mice.

Cytotoxic activity of peripheral blood and cerebrospinal fluid lymphocytes from patients with multiple sclerosis and other neurological diseases: analysis at the single cell level of the relationship of cytotoxic effectors and interferon-producing cells

The production of interferon (IFN alpha) in relationship to NK and ADCC activity of peripheral blood and cerebrospinal lymphocytes was examined at the single cell level in patients with multiple sclerosis (MS) and other neurological diseases (OND) compared with age- and sex-matched controls. IFN-producing cells were assessed by indirect immunofluorescent scoring of cytoplasmic IFN+ cells. Peak production of cytoplasmic IFN alpha in nylon wool-passed ( NWP ) cells occurred between 5 and 17 hr in vitro under the inductive stimulus of MOLT 4, K562, or antibody-coated Chang liver cells. The proportion of K562- and MOLT 4-induced IFN alpha-positive cells in the total lymphocyte and target-binding cell (TBC) population was significantly lower in MS NWP -peripheral blood lymphocytes (PBL) than in OND and normal controls; this was in direct relationship to a decreased percentage of NK cells in MS PBL. In contrast MS cells responded the same as controls (total IFN+ cells) or higher than controls (IFN+-TBC) after IFN alpha induction by antibody-coated Chang, the ADCC target, in parallel with elevated ADCC activity by MS PBL. MS CSF contained a higher proportion of total IFN+ cells but a similar proportion of IFN+-TBC as their homologous NWP PBL population. In OND CSF, both the percentage of total IFN+ and the percentage of IFN+-TBC were higher than in OND blood and higher than their respective MS CSF populations. The relationship of IFN-producing cells in the central nervous system (CNS) to putative cytotoxic cells is discussed.

Enhanced K-cell activity in the peripheral blood of patients with malignant disease

We have analysed the influence of human malignant, inflammatory and infectious disease on the capacity of peripheral lymphocytes to mediate antibody-dependent haemolysis. The application of an enzyme-like kinetic model for measurement of maximal cytotoxic function has permitted reproducible and sensitive determinations of the K-cell function. The results show that malignant disease is associated with enhancement of ADCC capacity.