Modulation of the adherence of human lymphocytes to measles-infected cells by prostaglandin E1: A differential effect on lymphocyte subpopulations

Prostaglandins of the E series (PGE) may serve as important regulators of human immune responsiveness. The present study was designed to examine the possibility that PGE may effect human lymphocyte function by the modulation of surface receptors. The presence of surface binding sites on human lymphocytes for measles virus antigens was studied using a rosette adherence assay. We observed that the addition of PGE₁ increased the proportion of measles-infected cells (Hela-Kll) with adherent lymphocytes (75% increase at 3 × 10⁻⁶ M PGE₁). PGE was observed to enhance the adherence of purified normal peripheral T cells (87%) and T lymphoid cells (Molt 3) (27%). In contrast, no significant change in normal peripheral B cell or B lymphoid cell (Raji) adherence was observed with the addition of PGE. These results are consistent with a selective modulation of surface measles virus binding sites by PGE₁ on T and not B lymphoid cells.     

Modulation of the adherence of human lymphocytes to measles-infected cells by prostaglandin E1: a differential effect on lymphocyte subpopulations

Prostaglandins of the E series (PGE) may serve as important regulators of human immune responsiveness. The present study was designed to examine the possibility that PGE may effect human lymphocyte function by the modulation of surface receptors. The presence of surface binding sites on human lymphocytes for measles virus antigens was studied using a rosette adherence assay. We observed that the addition of PGE1 increased the proportion of measles-infected cells (Hela-Kll) with adherent lymphocytes (75% increase at 3 x 10(-6) M PGE1). PGE was observed to enhance the adherence of purified normal peripheral T cells (87%) and T lymphoid cells (Molt 3) (27%). In contrast, no significant change in normal peripheral B cell or B lymphoid cell (Raji) adherence was observed with the addition of PGE. These results are consistent with a selective modulation of surface measles virus binding sites by PGE1 on T and not B lymphoid cells.     

Regulation by prostaglandin E2 of interleukin release by T lymphocytes in mucosa

Regulation of immune cell activation in lymphocyte-bearing human tissues is a pivotal host function, and metabolites of arachidonic acid (prostaglandin E₂ in particular) have been reported to serve this function at non-mucosal sites. However, it is unknown whether prostaglandin E₂ is immunoregulatory for the large lymphocyte population in the lamina propria of intestine; whether low (nM) concentrations of prostaglandin E₂ modulate immune responses occurring there; and whether adjacent inflammation per se abrogates prostaglandin E₂'s regulatory effects. To address these issues, intestine-derived lymphocytes and T hybridoma cells were assessed, T cell activation was monitored by release of independently quantitated lymphokines, and dose-response studies were performed over an 8-log prostaglandin E₂concentration range. IL-3 release by normal intestinal lamina propria mononuclear cells was reduced (up to 78%) in a dose-dependent manner by prostaglandin E₂, when present in as low a concentration as 10⁻¹⁰M. PGE₂ also inhibited(by ≥ 60%) mucosal T lymphocytes' ability to destabilize the barrier function of human epithelial monolayers. Further, with an intestine-derived T lymphocyte hybridoma cell line, a prostaglandin E₂ dose-dependent reduction in IL-3 and IL-2 (90 and 95%, respectively) was found; this was true for both mitogen- and antigen-driven T cell lymphokine release. Concomitant [³H] thymidine uptake studies suggested this was not due to a prostaglandin E²-induced reduction in T cell proliferation or viability. In contrast, cells from chronically inflamed intestinal mucosa were substantially less sensitive to prostaglandin E², e.g., high concentrations (10⁻⁶ M) of prostaglandin E² inhibited IL-3 release by only 41%. We conclude that prostaglandin E² in nM concentrations is an important modulator of cytokine release from T lymphocytes derived from the gastrointestinal tract, and it may play a central role in regulation of lamina propria immunocyte populations residing there. © 1996 Wiley-Liss, Inc.     

Augmentation of prostaglandin and thromboxane production in vitro by monocytes exposed to histamine-induced suppressor factor (HSF)

A possible mechanism to explain the suppression of mitogen-induced lymphocyte proliferation in vitro by histamine-stimulated mononuclear cells was investigated. In initial experiments, the inhibitory action of histamine-induced suppressor factor (HSF) on lymphocyte proliferation was documented to be reduced by the addition of indomethacin (1 μg/ml). Moreover, the addition of exogeneous PGE₂ (10^?7-10^?8 M) to mononuclear cell cultures reconstituted HSF activity in the presence of indomethacin. In order to ascertain the nature of the target cell responding to HSF, control and suppressor supernatants were incubated with human lymphocytes or monocytes (5 × 10⁶ cells/ml) for 24 hr. Following incubation, the supernatants were assayed for their content of prostaglandin E₂, F_2α, and thromboxane B₂. Monocytes (but not lymphocytes) incubated with supernatants containing HSF increased their production of prostaglandin E₂, F_2α, and thromboxane B₂ by 169, 53, and 49%, respectively. Suppressor supernatants were generated with histamine or an H-2 agonist (dimaprit) and chromatographed by gel filtration on Sephadex G-100. The elution profiles for the factor(s) inducing suppression of lymphocyte proliferation (25–40,000 daltons) and augmenting PGE₂ production (25,000 daltons) overlapped but were not identical. Collectively, these data suggest that HSF-mediated inhibition of lymphocyte proliferation may occur in part through the augmented production of prostaglandins and/or thromboxane B₂ by human monocytes.     

High-affinity binding sites for prostaglandin E on human lymphocytes.

Binding sites on human lymphocytes for prostaglandins were examined by incubating cells with [³H]prostaglandin (PG) A₁, E₁, E₂, F_1α, and F_2α. Specific reversible binding for [³H]PGE₁ and E₂ was found with a K_d of ~2 × 10^?9M and a B max of ~200 binding sites per cell, assuming uniform distribution. We detected no specific binding of [³H]PGA₁, F_1α, or F_2α to lymphocytes. Also, the addition of 10- to 1000-fold greater amounts of unlabeled PGA, F_1α, or F_2α did not inhibit the binding of [³H]PGE. The time course of [³H]PGE binding appeared to be bimodal with one component complete within 5 min at 37 °C and another component of binding increasing over a 40-min incubation. We feel that the rapid component of binding may represent cell surface receptors for PGE while the slower component may represent a specific uptake mechanism for PGE into the cell. Glass adherent cells had fewer binding sites than nonadherent cells. Preincubation of the cells overnight resulted in a loss of binding sites.     

A comparison of the 8-hydroxydeoxyguanosine,chromosome aberrations and micronucleus techniques for the assessment of the genotoxicity of mercury compounds in human blood lymphocytes

We compared the mechanism of action of micronuclei (MN), unstable chromosome aberrations, and 8-hydroxydeoxyguanosine (8-OHdG) levels to evaluate the genotoxicity of methyl mercuric chloride (CH₃HgCl) and mercuric chloride (HgCl₂) in human peripheral lymphocytes. The chromosome aberrations in human peripheral lymphocytes exposed to various concentrations of CH₃HgCl or HgCl₂ increased in a concentration-dependent manner and were significantly higher than the control when the cells were incubated with 1 × 10⁻⁵ M (HgCl₂) or 2 × 10⁻⁶ M (CH₃HgCl). The increase in the incidence of micronucleated lymphocytes was significant among the exposed groups, being 2 × 10⁻⁵ M (HgCl₂) and 5 × 10⁻⁶ M (CH₃HgCl) compared with the control. CH₃HgCl was about 4-fold more potent than HgCl₂. We determined the 8-OHdG levels in human peripheral blood mononuclear cells(PBMC) and found that they were significantly higher in the exposed groups at 1 × 10⁻⁵ M (HgCl₂) and 5 × 10⁻⁶ M (CH₃HgCl) compared with the control. A detectable (p < 0.05) increase in the level of 8-OHdG was induced by CH₃HgCl at a concentration that was about 50% of the amount of HgCl₂ required to produce a similar response. The data confirmed the value of the MN and/or chromosome aberration assays for assessing of HgCl₂- and/or CH₃HgCl-induced genotoxicity, and indicated that they are about the same concentration as the 8-OHdG assay. The presence of genotoxic effects in peripheral blood lymphocytes exposed to the mercuric compounds indicated by the chromosome aberrations and the MN assays could be partly due either to the disturbance of the spindle mechanism, or to the elevated level of 8-OHdG brought by the generation of reactive oxygen species.     

Myocardial actions of prostaglandins in isolated cat cardiac tissue.

The inotropic responses to prostaglandins (PG) A₁, E₁, E₂ and F_2α were studied in isolated cat myocardial tissue. PGA₁ and F_2α exhibited no significant inotropic effects, whereas, PGE₂ and PGE₁ produced negative inotropic effects at concentrations of 2.8 × 10⁻⁷ and 2.8 × 10⁻⁶ M in isolated cat papillary muscles.In isolated perfused cat hearts, PGE₁ (2.8 × 10⁻⁶M) produced a negative inotropic effect along with a significant increase in coronary flow. As flow declined, the negative inotropic effect became more severe. PGE₁ at 2.8 × 10⁻⁹ M produced a sustained increase in coronary flow and oxygen consumption with no inotropic effect. PGE₂ and F_2α did not exert significant changes in coronary flow or contractile force.Thus prostaglandins do not appear to exert significant positive inotropic effects at physiologic or at generally accepted pharmacologic concentrations in isolated cat heart preparations. At extremely high concentrations, prostaglandins E₁ and E₂ exert a negative inotropic effect; however, this would not explain the protective effect of these prostaglandins in circulatory shock.     

Contractile responses of longitudinal and circular smooth muscle of the canine stomach to prostaglandins E and F2α

Muscle strips were excised from the circular and longitudinal layers of the fundus, corpus and antrum, and from the inner portion of the pyloric ring. In general prostaglandin(PG)F₂α as well as PGE₁ and PGE₂ stimulated the longitudinal muscle. However, there were remarkable regional differences. The sensitivity to PGs was greatest in the fundus and corpus (threshold near 10⁻¹⁰ mol/1) and only weak in antrum (threshold 5·10⁻⁸ to 10⁻⁷ mol/1). In longitudinal antrum strips acetylcholine induced a combined phasic-tonic response, whereas PGs produced purely phasic responses. The effects of PGF_2α and PGE on the circular layer were complex. PGF_2α produced excitatory responses in circular fundus and corpus similar to those in the longitudinal layer of the same regions. PGE produced dual responses in circular fundus (excitation at low concentration and strong inhibition at concentration of 10⁻⁷ mol/1). In circular corpus PGE induced pure inhibition (threshold near 10⁻⁹ mol/1). In circular antrum and inner pylorus both PGE and PGF_2α produced inhibition of the phasic activity (threshold 10⁻⁸ to 10⁻⁷ for antrum and 10⁻⁹ mol/1 for inner pylorus). These effects of PGs appeared in the presence of adrenergic and cholinergic blocking agents as well as of tetrodotoxin and were therefore, direct effects on smooth muscle. Indomethacin (10⁻⁷–10⁻⁶ mol/1) suppressed spontaneous tone of the fundus and corpus and increased phasic activity of inner pylorus. This indicates that endogenous PG synthesis may be involved in the control of spontaneous activity in gastric muscle.     

Periodate-induced lymphocyte transformation : II. Character of response and comparison with phytohemagglutinin and pokeweed mitogen stimulation

Sodium metaperiodate is mitogenic for human peripheral lymphocytes. Evidence of stimulation can be detected as increased thymidine incorporation at 72 h after only 10 sec of exposure to the IO₄⁻. The degree of response varies with lymphocytes from different donors, but maximum stimulation for the healthy donors studied was obtained at concentrations of IO₄⁻ between 10⁻³ M and 4 × 10⁻³ M. Concentrations of 8 × 10⁻³ M and above are non-stimulatory and toxic. Exposures to optimum concentrations for 1 h or longer result in essentially no stimulation and inincreased cell death. However, a significant response to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) remains. The kinetics of response over a 4 day culture period are similar for IO₄⁻, PHA and PWM. The morphology of the blast cells and the degree of response suggest that the IO₄⁻ responsive lymphocyte population may be more closely related to the PWM stimulated cells than the PHA responsive lymphocytes.     

Different mechanisms are responsible for the contractile effects of histaminergic compounds on isolated intestinal smooth muscle cells

The effects of histamine and dimaprit on intestinal smooth muscle contractility were investigated on isolated cells from longitudinal muscle of the guinea pig ileum. Both histamine (10⁻¹⁴–10⁻¹⁰ M) and dimaprit (10⁻¹³–10⁻¹⁰ M) exerted a concentration-dependent contraction of intestinal cells, causing a maximum decrease in cell length of about 20%. This effect was not significantly different from that induced by cholecystokinin-octapeptide (CCK-8) 10⁻⁹ M. The concentration-response curves to histamine and dimaprit were shifted to the left in the presence of the histamine H₂-receptor antagonist famotidine (10⁻⁷ M) indicating the occurrence in the smooth muscle of H₂ receptors mediating relaxation. Whereas the contraction produced by histamine was competitively antagonized by the H₁ receptor antagonist mepyramine (10⁻⁸ M), neither mepyramine (10⁻⁷ M) nor temelastine (10⁻⁷ M) did modify the contractile effect of dimaprit. In contrast, atropine (10⁻⁸ M) significantly depressed the maximum response to dimaprit without affecting that exerted by histamine. These data indicate that histamine and dimaprit can modify intestinal contractility, by acting via different mechanisms; while the contractile action of histamine is related to H₁ receptor activation, that produced by dimaprit involves cholinergic pathways.     

17β-Estradiol regulation of protein kinase C activity in chondrocytes is sex-dependent and involves nongenomic mechanisms

17β-Estradiol (E₂) regulates growth plate chondrocyte differentiation in both a sex- and cell maturation–dependent manner, and the sex-specific effects of E₂ appear to be mediated in part by membrane events. In this study, we examined whether E₂ regulates protein kinase C (PKC) in a cell-maturation and sex-specific manner and whether E₂ uses a nongenomic mechanism in regulating this enzyme. In addition, we determined if PKC mediates the E₂-dependent stimulation of alkaline phosphatase activity seen in chondrocytes. Confluent, fourth passage resting zone (RC) and growth zone (GC) chondrocytes from male and female rat costochondral cartilage were treated with 10⁻¹⁰ to 10⁻⁷ M E₂. E₂ caused a dose-dependent increase in PKC in RC and GC cells from female rats. Peak stimulation was at 90 min. Increased PKC was evident by 3 min in both RC and GC and was still evident in RC cells at 720 min, but in GC cells activity returned to baseline by 270 min. Actinomycin D had no effect at 9, 90, 270, or 720 min, but there was a small decrease in E₂-stimulated PKC in RC treated with cycloheximide at 90 and 270 min and in GC treated for 90 min. E₂ increased cytosolic and membrane PKC at 9 min and by 90 min promoted translocation of PKC activity from the cytosol to the membranous compartment of female RC cells. Antibodies specific for the α, β, δ, ε, and ζ isoforms of PKC revealed that PKCα in female GC and RC cells is activated by E₂. There was a small, but statistically significant, increase in PKC in male RC cells in response to E₂, but it was not dose-dependent, and no effect of E₂ was noted in male GC cells. 17α-estradiol, an inactive isomer of E₂, did not affect PKC specific activity in RC or GC cells from either female or male rats. Chelerythrine, a specific inhibitor of PKC, inhibited E₂-dependent alkaline phosphatase activity, indicating that E₂ mediates its rapid effects on alkaline phosphatase via PKC. J. Cell. Physiol. 176:435–444, 1998. © 1998 Wiley-Liss, Inc.     

Prostaglandin synthesis by rat uterine homogenates in the presence of copper ions,and the effects of indomethacin and salicylic acid

While no significant effects on the in vitro production of PGF₂α by homogenates of rat estrous uteri were observed in the presence of 10⁻³ and 10⁻⁶M Cu²⁺, the presence of Cu²⁺ at 10⁻⁴ and 10⁻⁵M was found to stimulate production with maximal synthesis of PGF₂α occurring with 10⁻⁴M Cu²⁺. By contrast, the synthesis of PGE₂ and PGI₂ (determined as 6-keto PGF₁α) were unaffected at all of the different Cu²⁺ concentrations used. When indomethacin and salicylic acid were tested for their effects on the Cu²⁺-mediated levels of PG synthesis by the homogenates, indomethacin (at 20μM) was found to cause similar pronounced decreases in PGF₂α, PGE₂ and 6-keto PGF₁α whereas salicylic acid (400μM) showed preference towards suppressing PGE2 and 6-keto PGF₁α production.     

Effects of some 1,4‐dihydropyridine Ca antagonists on the blast transformation of rat spleen lymphocytes

Ca antagonists of different classes (verapamil, nifedipine, nicardipine, diltiazem) in a concentration of 10⁻⁵ m and higher are known to suppress Ca²⁺ transport into the lymphocyte cytosol, changing a normal response of lymphocytes to mitogens and antigens and so inhibiting their proliferation, as well as IL‐2‐induced cell proliferation, and their receptor expression on the surface of lymphocytes without cell cytotoxicity. In the present work we studied the effect of some 1,4‐dihydropyridines (DHP) such as nimodipine, nicardipine, nifedipine, niludipine, cerebrocrast, etaftoron, as well as metabolites of cerebrocrast: compounds 7 and 8, (four of the last were synthesized in the Latvian Institute of Organic Synthesis) on rat spleen isolated lymphocyte activation and proliferation in vitro following stimulation with the mitogens concanavalin A (Con A) and recombinant interleukin‐2 (IL‐2), insulin and insulin antibodies. Based on the experimental results we conclude that in low concentrations (10⁻⁷ to 10⁻⁹ M ) the tested 1,4‐DHP Ca antagonists stimulated the process of rat spleen lymphocyte proliferation and DNA synthesis, especially cerebrocrast. It is proposed that these Ca antagonists, as well as causing a concentration decrease of Ca²⁺, also activated phosphodiesterase, which in its turn, suppressed cAMP accumulation in the lymphocytes and eventually increased Ca²⁺ ion transport in the cells. Cerebrocrast among all the studied DHP Ca antagonists was the most potent in studies of activation of the lymphocytes in the presence of Con A, IL‐2 and insulin, which indicates the number of suppressor and helper lymphocytes and formation of insulin and interleukin receptors on their membrane surface. The increase in the lymphocyte suppressive activity produced by this compound effect can prevent diabetes mellitus types I and II at the stages of pre‐diabetes, early and distant diabetes, from hyperexpression of insulin and its receptor antibodies. Copyright © 1999 John Wiley & Sons, Ltd.     

The effect of catecholamines and prostaglandins upon human and rat erythrocytes

Both human and rat erythrocytes respond to low doses (10⁻¹¹-10⁻⁹ M) of L-isoproterenol and Lepinephrin with an increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters. The receptors in both cell types have many of the characteristics of β-receptors for catecholamines. However, hormone-receptor interaction in the human cell does not lead to an increase in intracellular cyclic AMP concentration, but in the rat cell, hormone-receptor interaction does lead to a significant increase in cylic AMP content. Thus, catecholamine-β-receptor interaction, at least in the human red cell, leads to a change in red cell properties which are not mediated by adenylate cyclase activation. Likewise, prostaglandin E₂, at 10⁻¹²-10⁻¹⁰ M, causes an increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters, but it also does not increase the cyclic AMP content of the human erythrocyte but does increase that of the rat erythrocyte. Nevertheless, exogenous cyclic AMP, when added at a concentration of 10⁻⁸ M to washed human erythrocytes, increases the degree of hypotonic hemolysis. Conversely, prostaglandin E₁, at 10⁻¹²-10⁻¹⁰ M, causes a decreased degree of hypotonic hemolysis and an increased rate of filtration through a standard filter. Both prostaglandin E₂ and the catecholamines decrease the size of a rapidly exchangeable calcium pool, and prostaglandin E₁ increases it.     

Prostaglandins and the rat seminal vesicle: Effects of mating and adrenergic stimulation

The concentrations of PGE, PGF, and 6-keto-PGF_1α were increased in rat seminal vesicle tissue following mating activity. Likewise, synthesis of PGE and PGF was stimulated by epinephrine (3 × 10⁻⁷to 3 × 10⁻⁶ M) in tissues and media from incubations of intact rat seminal vesicles. The stimulation was inhibited by phentolamine, an α-adrenoreceptor blocking agent. Carbamylcholine (2 × 10⁻⁶ M) and bradykinin (1 × 10⁻⁶ M) had no effect on PGE or PGF synthesis, even though both compounds stimulated contractility of the rat seminal vesicle at these concentrations. These data suggest that mating and adrenergic stimulation increase prostaglandin synthesis in] the rat seminal vesicle, probably through an α-adrenergically mediated mechanism.     

Lymphocyte adherence in multiple sclerosis: Lack of virus specificity

The virus specificity of adherence of peripheral blood mononuclear leukocytes from patients with multiple sclerosis and from age- and sex-matched healthy volunteers to tissue culture cells infected with measles virus, Newcastle disease virus, and vesicular stomatitis virus was studied. Lymphocyte adherence to uninfected cells is uniformly low (5–15% tissue culture cells with > 3 lymphocytes adhered). Adherence to cells infected with virus is enhanced 2- to 4-fold in controls and 2- to 10-fold in patients with multiple sclerosis. Virus-specific antigen, antiserum, and receptor, at least in part, inhibited adherence to all cells tested. It is concluded from these studies that increased lymphocyte adherence in multiple sclerosis is not measles virus specific.     

Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates release of somatolactin (SL)-α and SL-β from cultured goldfish pituitary cells via the PAC1 receptor-signaling pathway,and affects the expression of SL-α and SL-β mRNAs

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide that stimulates the release of adenohypophyseal hormone from the pituitary in fish. In the goldfish, PACAP induces the release of somatolactin (SL), in particular, from cultured pituitary cells. SL belongs to the growth hormone and prolactin family, and comprises two molecular variants termed SL-α and SL-β in goldfish. However, there is no information about the involvement of PACAP in the regulation of SL-α and SL-β release and the expression of their mRNAs. Therefore, we examined the effect of PACAP on SL-α and SL-β release from cultured goldfish pituitary cells. Treatment with PACAP (10⁻¹⁰–10⁻⁷ M) increased the release of both SL-α and SL-β. The stimulatory action of PACAP (10⁻⁹ M) on SL-α and SL-β release was blocked by treatment with a PACAP-selective receptor (PAC₁R) antagonist, PACAP_(6–38) (10⁻⁶ M). We also examined whether PACAP affects the expression of SL-α and SL-β mRNAs in cultured pituitary cells. Treatment with PACAP (10⁻⁹ and 10⁻⁸ M) for 6 h decreased the expression level of SL-α mRNA but increased that of SL-β mRNA. The action of PACAP (10⁻⁸ M) on SL-β mRNA expression was blocked by treatment with PACAP_(6–38) (10⁻⁶ M), whereas PACAP_(6–38) elicited no change in the expression of SL-α mRNA. These results indicate that in cultured goldfish pituitary cells, PACAP stimulates the release of SL-α and SL-β, and expression of SL-β mRNA, via the PAC₁R-signaling pathway. However, the mechanism whereby PACAP inhibits the expression of SL-α mRNA does not seem to be mediated by PAC₁R signaling.     

A possible role of prostaglandins in the inhibition of natural and antibody-dependent cell-mediated cytotoxicity against tumor cells

We recently observed that certain tumor cell lines in tissue culture produced prostaglandins and that increased production occurred when the tumor cells were exposed to lymphocytes. The present experiments tested the effect of prostaglandins E₁ and E₂ on natural and antibody-dependent lymphocyte cytotoxicity against the same target cells in order to determine whether the production of prostaglandins by the tumor cells might influence the efficacy of the cellular immune response. Target cell lines T₂₄ and HCV₂₉ were labeled with ⁵¹Chromium and incubated at 37 °C for various times with lymphocytes prepared from venous blood of normal donors. Antiserum to T₂₄ and varying concentrations of prostaglandin E₁ or E₂ were added to the samples prior to incubation. In some experiments, lymphocytes or labeled target cells were preincubated with prostaglandins and then washed prior to their addition to the assay tubes. Cytotoxicity was determined by measuring the release of ⁵¹Chromium from the target cells after incubation. Both prostaglandins E₁ and E₂ inhibited natural and antibody-dependent lymphocyte cytotoxicity against the target cells. The effect appeared to represent a direct one on lymphocytes, and it was amplified by the presence of theophylline in the medium. Inhibition could be effected early on in lymphocyte/target cell interaction, and only a short exposure of lymphocytes to prostaglandins was required for the effect to be manifested. It thus appears that the production of prostaglandins by tumor cells may constitute a means by which the tumor cells subvert the effect of a cellular immune response that is directed against them.     

In vitro locomotion of allosensitized T lymphocyte clones in response to metabolites of arachidonic acid is subset specific

The effects of the arachidonic acid metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) on the in vitro random migration of cloned murine T lymphocytes (derived from limiting dilution analysis of a C57BL/6 anti-DBA/2 mixed leukocyte culture) were examined. Experiments were also performed to study the effects of the cyclooxygenase inhibitor indomethacin on both random lymphocyte migration and lymphocyte migration in the presence of PGE2. The responses of cloned lymphocytes to PGE2 and LTB4 were compared with those of unsensitized lymph node lymphocytes. PGE2 at 100 ng/ml significantly inhibited (p less than 0.001) the in vitro migration of helper clones of T lymphocytes, but had no effect on random migration of cytotoxic T cells or helper independent cytotoxic (HIT) cloned cells. In contrast, LTB4 significantly (p less than 0.001) enhanced the random locomotion of helper, cytotoxic, and "HIT" cloned cells at 0.1 and 0.3 ng/ml. The effects of both PGE2 and LTB4 were found to be completely reversible by cell washing. Indomethacin (10(-7) M) did not alter random migration of any of the clones, and in particular, did not affect the inhibition of helper lymphocyte migration induced by PGE2. Unsensitized bulk lymph node lymphocyte migration was not affected by either PGE2 or LTB4. The results suggest that modulation of lymphocyte locomotor function by environmental stimuli may depend on cellular activation, and the locomotor responses of activated lymphocytes to arachidonic acid metabolites may be subset specific.     

Surface mediated death of unconditioned Tetrahymena cells: Effect of physical parameters,growth factors,hormones, and surfactants

A new form of cell death has been observed. The death occurs at liquid-air interfaces when Tetrahymena cells are grown in a chemically defined medium (CDM) at low inocula. The cells die by lysis at the liquid-air interface (medium surface), which they reach due to negative gravitaxis as well as positive aerotaxis. When the cells are grown in a closed compartment, with no liquid-air interface, the death is not observed, and the cells proliferate. Cloning of cells in CDM is thus possible. The addition of effectors such as NGF (10⁻¹¹ M), EGF (10⁻¹⁰ M), PDGF (10⁻¹⁰ M), and insulin (10⁻¹⁰ M) to cells in CDM prevents the surface mediated death. Since detergents/surfactants like SDS (7 × 10⁻⁵ M), NP-40 (2 × 10⁻⁵ M), Tween 80 (10⁻⁴% w/v), Pluronic F-68 (10⁻⁷ M), and the biosurfactant surfactin (10⁻⁶ M) have the same effect, we suggest that the effectors act by stimulating the cells to exudate surfactant(s) of their own. Furthermore, lyzed cells and exudates from living cells (pre-conditioned medium) prevent the death. In conditions with liquid-air interfaces, certain physical parameters are of great importance for the survival of cells at low inocula. The parameters are the distance to the surface, the temperature, and the inoculum. By increasing the height of the medium, lowering the temperature, and increasing the inoculum of the culture, the survival can be greatly enhanced. There is no evidence for programmed cell death (PCD) or apoptosis. © 1996 Wiley-Liss, Inc.