Cannabinoids and the immune system

The effect of cannabimimetic agents on the function of immune cells such as T and B lymphocytes, natural killer cells and macrophages has been extensively studied over the past several decades using human and animal paradigms involving whole animal models as well as tissue culture systems. From this work, it can be concluded that these drugs have subtle yet complex effects on immune cell function and that some of the drug activity is mediated by cannabinoid receptors expressed on the various immune cell subtypes. However, the overall role of the cannabinoid system of receptors and ligands in human health and disease is still unclear and requires extensive elucidation. Further studies will define the precise structure and function of the putative immunocannabinoid system, the potential therapeutic usefulness of these drugs in chronic diseases such as acquired immune deficiency syndrome and multiple sclerosis, the effects of these agents on tumour growth and induction of apoptosis, and the potential anti-inflammatory and proinflammatory properties of cannabimimetic compounds. It is likely that the cannabinoid system, along with other neuroimmune systems, has a subtle but significant role in the regulation of immunity and that this role can eventually be exploited in the management of human disease.

The cannabinoid system and cytokine network

Many advances have been made in the last few years concerning our understanding of the receptors and ligands composing the cannabinoid system. Likewise, the science surrounding cytokine biology has advanced enabling us to measure these proteins more precisely as well as understand and interpret the meaning of changes in their levels. Scientists wishing to study the health consequences of smoking marijuana as well as understand the possible role of endogenous cannabimimetic ligands in immune regulation have continued to study the influence of these substances on the regulation and development of the cytokine network. Research has shown that two major cannabinoid receptor subtypes exist and that subtype 1 (CB1) is expressed primarily in the brain whereas subtype 2 (CB2) is expressed primarily in the periphery. A variety of ligands for these receptors based on the cannabinoid structure have been synthesized and studied as well as low affinity compounds, noncannabinoid ligands, and endogenous ligands derived from fatty acid eicosanoids. Highly selective receptor antagonists have also been introduced and studied. Synthetic, low affinity ligands such as (+)-HU-211 and DMH-11C have been shown to cause anti-inflammatory effects possibly through inhibiting the production and action of TNF-alpha and other acute phase cytokines. In addition, suppression of TNF and other cytokines such as GM-CSF, IL-6, IFNgamma, and IL-12 has also been seen following exposure to high affinity and psychoactive ligands such as marijuana and THC. However, some of these ligands have also been shown to increase rather than decrease interleukins such as IL-1, IL-4, IL-10, and IL-6, cytokines such as TNF-alpha, and chemokines such as IL-8, MIP-1, and RANTES. The endogenous ligand, anandamide, has been shown in culture to either suppress the proliferation response to prolactin or enhance the response to cytokines such as IL-3 and IL-6. This eicosanoid has also been shown to increase the production of interleukins and other cytokines. Cannabinoid receptors have been shown to be involved in some but not all of these effects. It is clear that psychoactive and nonpsychoactive compounds have demonstrated effects in vivo and in vitro on the production and function of a variety of cytokines. Depending upon the model system, these effects are often conflicting, and the involvement of cannabinoid receptors is unclear. However, enough evidence exists to suggest that the cannabinoid system significantly impacts the functioning of the cytokine network, and this association may provide clues to the mechanisms of certain immune diseases and form the basis for new immunotherapies.

The cannabinoid system and cytokine network

Many advances have been made in the last few years concerning our understanding of the receptors and ligands composing the cannabinoid system. Likewise, the science surrounding cytokine biology has advanced enabling us to measure these proteins more precisely as well as understand and interpret the meaning of changes in their levels. Scientists wishing to study the health consequences of smoking marijuana as well as understand the possible role of endogenous cannabimimetic ligands in immune regulation have continued to study the influence of these substances on the regulation and development of the cytokine network. Research has shown that two major cannabinoid receptor subtypes exist and that subtype 1 (CB1) is expressed primarily in the brain whereas subtype 2 (CB2) is expressed primarily in the periphery. A variety of ligands for these receptors based on the cannabinoid structure have been synthesized and studied as well as low affinity compounds, noncannabinoid ligands, and endogenous ligands derived from fatty acid eicosanoids. Highly selective receptor antagonists have also been introduced and studied. Synthetic, low affinity ligands such as (+)-HU-211 and DMH-11C have been shown to cause anti-inflammatory effects possibly through inhibiting the production and action of TNF-alpha and other acute phase cytokines. In addition, suppression of TNF and other cytokines such as GM-CSF, IL-6, IFNgamma, and IL-12 has also been seen following exposure to high affinity and psychoactive ligands such as marijuana and THC. However, some of these ligands have also been shown to increase rather than decrease interleukins such as IL-1, IL-4, IL-10, and IL-6, cytokines such as TNF-alpha, and chemokines such as IL-8, MIP-1, and RANTES. The endogenous ligand, anandamide, has been shown in culture to either suppress the proliferation response to prolactin or enhance the response to cytokines such as IL-3 and IL-6. This eicosanoid has also been shown to increase the production of interleukins and other cytokines. Cannabinoid receptors have been shown to be involved in some but not all of these effects. It is clear that psychoactive and nonpsychoactive compounds have demonstrated effects in vivo and in vitro on the production and function of a variety of cytokines. Depending upon the model system, these effects are often conflicting, and the involvement of cannabinoid receptors is unclear. However, enough evidence exists to suggest that the cannabinoid system significantly impacts the functioning of the cytokine network, and this association may provide clues to the mechanisms of certain immune diseases and form the basis for new immunotherapies.

Tumor necrosis factor induces resistance of macrophages to Legionella pneumophila infection

Legionella pneumophila is an ubiquitous opportunistic intracellular pathogen that replicates readily in thioglycollate-elicited peritoneal macrophages from genetically susceptible A/J mice. Treatment of macrophage cultures in vitro with tumor necrosis factor-alpha (TNF-alpha) induced resistance of the macrophages to infection by Legionella as compared with control macrophages treated with medium alone. Addition of small amounts of monoclonal antibody to TNF-alpha restored susceptibility of the macrophages. Furthermore, antibody to the proinflammatory cytokine interleukin-1 (IL-1) alpha/beta increased resistance, but recombinant IL-1 had little effect. Such decreased susceptibility to Legionella growth in anti-IL-1 antibody-treated cultures corresponded with enhanced levels of TNF-alpha in the supernatants of the treated cells. An antibody to another proinflammatory cytokine with known immunoregulatory properties (i.e., IL-6) had little or no effect on the ability of the macrophages to be infected by Legionella and, furthermore, treatment with recombinant IL-6, similar to recombinant IL-1, did not modify the ability of the cells to be infected in vitro. These results indicate that TNF-alpha is important in controlling L. pneumophila replication, and IL-1 can regulate TNF-alpha levels, affecting susceptibility of macrophages to infection with an intracellular opportunistic pathogen like Legionella.

Delta 9-tetrahydrocannabinol treatment suppresses immunity and early IFN-gamma, IL-12, and IL-12 receptor beta 2 responses to Legionella pneumophila infection

The marijuana cannabinoid, delta 9-tetrahydrocannabinol (THC), suppresses immunity to Legionella pneumophila and development of Th1 activity and cell-mediated immunity. In the current study, THC effects on cytokines regulating the development of Th1 cells were examined. BALB/c mice showed significant increases in serum IL-12 and IFN-gamma within hours of infection; however, the levels of these Th1-promoting cytokines as well as resistance to a challenge infection were suppressed by THC (8 mg/kg) injected 18 h before priming. The Th2-promoting cytokine, IL-4, was increased within hours of a Legionella infection and was further increased by THC treatment. These results suggested that THC injection suppressed the cytokine environment promoting Th1 immunity. In additional experiments, THC pretreatment and infection of IL-4 knockout mice showed that serum IL-12 and IFN-gamma were suppressed equally in both knockout and normal mice. This suggested that the drug-induced increase in IL-4 was not responsible for the decreases in serum IL-12 and IFN-gamma. However, THC treatment was shown to suppress the expression of IL-12 receptor beta 2 mRNA, indicating that, in addition to suppression of IL-12, THC injection suppressed the expression of IL-12 receptors. Finally, the role of cannabinoid receptors in Th1-promoting cytokine suppression was examined, and results with receptor antagonists showed that both cannabinoid receptors 1 and 2 were involved. It is suggested that suppression of Th1 immunity to Legionella is not due to an increase in IL-4 production but to a decrease in IFN-gamma and IL-12. Furthermore, both types of cannabinoid receptors are involved.

Pulmonary endothelial and epithelial integrity and neutrophil infiltration after endotoxin in interleukin-1 receptor knockout mice

Previously we found the structural integrity of the aortic endothelium was maintained after the administration of endotoxin in type 1 interleukin-1 (IL-1) receptor knockout mice. In this study, we investigated further the integrity of pulmonary vascular endothelium, airway epithelial, pulmonary microvasculature, and neutrophil infiltration into the microvasculature and respiratory air spaces. Adult male C57BL/129J wild-type mice and C57BL/129J knockout mice possessing a homozygous deletion of the type 1 IL-1 receptor received the following intraperitoneal injections; 1) Escherichia coli endotoxin (ENDT) (10 mg/kg), 2) ENDT (2 mg/kg given for 4 days), or (3) saline vehicle. Wild-type and knockout control animals receiving saline vehicle showed normal endothelial and epithelial ultrastructure with intact membranes. Pulmonary endothelial cell damage was found only in wild-type mice given a single 10 mg/kg endotoxin dose. Airway epithelial damage was found only in wild-type mice given a repetitive dose of endotoxin (2 mg/kg for 4 days). Neutrophil infiltration increased only in mice given a single dose of endotoxin (10 mg/kg) with the wild-type increasing by 32% and the knockouts by 6% compared with the saline control for that group respectively. Serum IL-6 and nitric oxide (indicators of septic shock severity and lethality) significantly increased only in the mice given 10 mg/kg of endotoxin. The maintenance of pulmonary endothelial and epithelial cell integrity and the decrease of neutrophil infiltration in the IL-1 knockout mice suggest that IL-1 contributes significantly to the severity of endotoxin-induced sepsis.

Amyloid-beta peptide induced inflammatory reaction is mediated by the cytokines tumor necrosis factor and interleukin-1

A chronic inflammatory response possibly mediated by amyloid-beta (A beta) is believed to be a major factor in the pathology of Alzheimer's disease (AD). Recently, we demonstrated that in vivo administration of A beta produces an inflammatory response and vascular disruption as seen in the brains of AD patients. In an inflammatory response, leukocyte activation and extravasation involves cytokine production. Previous studies have indicated that immune interactions exist between the central nervous system and the peripheral immune mechanisms in AD. Increased levels of interleukin-1 beta (IL-1 beta) have been detected in brain tissue, cerebrospinal fluid, and blood/serum from AD patients. In addition, A beta stimulated the production of tumor necrosis factor-alpha (TNF-alpha) in brain astrocytes and murine monocytes. Using an animal model we investigated the role of the cytokines, TNF-alpha and IL-1 beta, in the A beta-induced inflammatory response. Adult male rats were perfused via an intra-aortic cannula with either A beta alone, interleukin-1 receptor antagonist (IL-1 ra) plus A beta, tumor necrosis factor-binding protein (TNF-bp) plus A beta or sterile saline. Serum analysis for TNF-alpha, IL-1 beta, A beta and NO showed a significant increase in TNF-alpha and A beta but not in IL-1 beta or NO after the injection of A beta. Control values for serum A beta averaged 1.6 ng/ml and in rats injected with A beta, 99.6% of this peptide was removed from the blood within 30 min. The mesenteric arterioles and venules were video recorded for 1-2 h and then processed for electron microscopy (EM). In rats given A beta alone there was extensive vascular disruption, including endothelial and smooth muscle damage with leukocyte adhesion and migration. Animals receiving either IL-1 ra or TNF-bp before A beta showed no in vivo leukocyte extravasation or vascular damage under EM. Therefore, the cytokines TNF-alpha and IL-1 beta seem to mediate the vascular disruption and inflammatory response initiated by A beta. Antagonism of these pro-inflammatory cytokines may offer new avenues for AD therapy.

Endothelial structural integrity is maintained during endotoxic shock in an interleukin-1 type 1 receptor knockout mouse

The derangement of arterial endothelial cell morphology is a good indicator of a severe shock state. Because interleukin (IL)-1 has been implicated in this process, we examined the structural integrity of aortic endothelial cells in conjunction with serum IL-6 concentrations and nitric oxide levels, which are known to increase during endotoxemia in animals genetically devoid of the type 1 IL-1 receptor. Endotoxin (10 mg/kg Escherichia coli, injected intraperitoneally) (LD100) or saline vehicle was administered to adult male C57BL/129J wild-type control mice and C57BL/129J knockout mice possessing a homozygous deletion of the type 1 IL-1 receptor. The integrity of the aortic endothelium was determined by comparisons of ultrastructure. Mice injected with sterile vehicle showed normal endothelial ultrastructure with intact membranes. Wild-type and knockout control animals receiving saline vehicle showed a complete aortic endothelium (29.11 +/- .27 and 30.85 +/- .21 intact endothelial cells per millimeter of internal elastic lamina (IEL), respectively, p = N.S.). Endotoxin-treated wild-type animals showed extensive endothelial damage with most sections showing only denuded IEL on the luminal surface (1.83 +/- .38 cells/mm IEL, p < .001 vs. control). Knockout animals treated with endotoxin showed complete maintenance of endothelial structural integrity (34.08 +/- .57 cells/mm IEL, p < .001 vs. endotoxin-treated wild type) with ultrastructural morphology appearing identical to those given saline vehicle. Also, no apparent correlation was observed between serum IL-6 concentrations or serum nitric oxide levels and aortic endothelial damage. The maintenance of endothelial integrity in animals devoid of the IL-1 receptor confirms earlier observations of endothelial cell protection with IL-1 receptor antagonism and suggests that IL-1 contributes significantly to sepsis-induced endothelial damage.

Injection of complementary DNA encoding interleukin-12 inhibits tumor establishment at a distant site in a murine renal carcinoma model

Interleukin (IL-12) protein has been shown to elicit diverse immunological responses and potent antitumor activity. We demonstrate here that intradermal injection of IL-12 cDNA induces systemic biological effects characteristic of the cytokine in vivo. Intradermal injection of IL-12 cDNA resulted in local expression of IL-12 mRNA, which correlated with a 10-fold increase in natural killer activity and a 3-4-fold increase in anti-CD3-induced IFN-gamma production in cultured splenocytes. Furthermore, when challenged with Renca tumor cells at a distant site, the day of tumor emergence was significantly delayed, and tumor growth was reduced in mice that received IL-12 cDNA, compared to mice given injections of plasmid vector alone. A number of the mice receiving IL-12 cDNA injections remained tumor free months after tumor challenge. In contrast to mice receiving recombinant IL-12 protein, no splenomegaly was detected when natural killer activity was significantly induced in mice receiving injections of IL-12 cDNA. Because purified plasmid DNA is more economical to prepare and has a longer shelf-life than recombinant proteins, and intradermal administration of cDNA encoding IL-12 did not cause splenomegaly, our findings suggest that the in vivo injection of cDNA encoding IL-12 may be a less toxic and more cost-effective alternative to IL-12 protein therapy in some clinical or experimental therapeutic applications.

Secondary immunity to Legionella pneumophila and Th1 activity are suppressed by delta-9-tetrahydrocannabinol injection

Resistance to infection with Legionella pneumophila is primarily dependent upon cell-mediated immunity rather than humoral immunity. Recent evidence suggests that activation of cell-mediated immunity depends on Th1 cells and activation of humoral immunity depends on Th2 cells. In this report, delta 9-tetrahydrocannabinol (THC), the major psychoactive cannabinoid of marijuana and an immunomodulator, suppressed development of secondary immunity to L. pneumophila, which correlated with a reduction in Th1 activity. BALB/c mice, infected with a primary sublethal dose of L. pneumophila, developed resistance to a larger challenge infection 3 to 4 weeks later. However, intravenous injection of THC (4 mg/kg of body weight) 1 day prior to primary infection resulted in increased mortality after the challenge infection. The level of anti-L. pneumophila antibodies in serum increased in both THC-treated and control mice; however, in the THC group IgG1 antibodies which are stimulated by Th2 cells were elevated while Th1-regulated, IgG2a antibodies were depressed. Furthermore, cultured splenocytes from THC-treated mice had less L. pneumophila-specific lymphoproliferation, indicating a deficiency in cell-mediated immunity. Normal mouse splenocytes treated in vitro with THC and pokeweed mitogen showed suppressed production of gamma interferon, a cytokine associated with Th1 cells, but increased production of interleukin 4, a cytokine produced by Th2 cells. Splenocytes from THC-treated mice, stimulated in vitro with either pokeweed mitogen or anti-CD3 antibodies, also produced less gamma interferon, indicating less Th1 activity in these mice. These results suggest that THC decreases the development of anti-L. pneumophila immunity by causing a change in the balance of Th1 and Th2 activities.

A rapid colorimetric assay for evaluating Legionella pneumophila growth in macrophages in vitro

A rapid colorimetric technique for in vitro quantitation of Legionella pneumophila intracellular proliferation in macrophages is described. The assay is based on the electron transport activity of metabolically active L. pneumophila. The yellow tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is cleaved by the mitochondrial activity of viable L. pneumophila, forming a dark formazan derivative with an absorption spectrum different from that of the native compound. The MTT method for measuring intracellular growth of L. pneumophila closely correlated with the CFU assay. The ability of macrophages from the A/J mouse strain to support intracellular growth of L. pneumophila and the ability of desferrioxamine to restrict L. pneumophila intracellular proliferation were confirmed by both methods. The MTT assay offers the advantages of rapidity, simplicity, and cost efficiency over the CFU assay, since it can be performed in the same flat-bottom microtiter plate with measurement in an enzyme-linked immunosorbent assay reader, allowing efficient processing of large numbers of samples.

Antibody-mediated enhancement of Legionella pneumophila-induced interleukin 1 activity

The ability of antibody specific for Legionella pneumophila to enhance the induction of interleukin 1 (IL-1) production by murine peritoneal, splenic, and pulmonary macrophages in response to the bacterium was examined. Two preparations of L. pneumophila were utilized, a formalin-killed whole-cell preparation and viable bacteria. We measured both secreted (sIL-1) and cell membrane-associated (mIL-1) activities after incubation of the macrophages with the bacterial preparations in the presence or absence of the antibody. Both bacterial preparations induced sIL-1 and mIL-1 activities in each of the macrophage populations tested. These activities were generally enhanced by pretreating the bacteria with antibody, with the greatest enhancing activity observed for the formalin-killed preparations at lower doses of bacteria.

Cocaine suppresses proliferation of phytohemagglutinin-activated human peripheral blood T-cells

Cocaine has been reported to modulate the immune system of experimental animals. Also, we observed that the drug suppresses the phytohemagglutinin (PHA)-induced proliferation of human peripheral blood mononuclear cells (PBMCs) but at concentrations extremely high relative to those seen in the blood of drug abusers. This suggested that cocaine had a relatively weak effect when tested under conditions of optimum proliferation. We, therefore, decided to examine the effect of lower concentrations of cocaine on suboptimum PHA-induced proliferation. At 0.09-12 microM, cocaine had no effect on the proliferation of PBMC in response to 0.2 micrograms/ml PHA. However, depleting the population of B-cells and monocytes resulted in a drug-induced suppression of the residual T-cells. Maximum suppression by cocaine was observed at 3 microM with both higher and lower concentrations of the drug causing less suppression. Suppression of proliferation was not influenced by either the age or sex of the peripheral blood lymphocytes (PBL) donors. The suppression of T-cell-enriched PBLs induced by cocaine could be eliminated by increasing the dose of the mitogen but was enhanced by preincubating the cells with the drug for 24 h. Also, the drug suppressed cytosolic free calcium mobilization in Fura 2/AM loaded enriched T-cell populations. These results show that cocaine moderately but consistently suppresses PHA-induced proliferation of T-cells from random blood donors at drug concentrations observed in drug abusers. The suppression is only evident under conditions of suboptimum proliferation and is accompanied by a corresponding decrease in the mobilization of cytosolic free calcium. It is suggested that the weak suppressive effect of cocaine is reversed by either helper factors produced by accessory cells or increasing concentrations of mitogen. These factors when present possibly overcome a drug-induced reduction in calcium mobilization and lymphocyte activation.

Differing effects of delta-9-tetrahydrocannabinol (THC) on murine spleen cell populations dependent upon stimulators

Delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, can suppress the immune response, both in vitro and in vivo. In the present study, THC was found to either up-regulate or down-regulate lymphocytes depending on the method of stimulation. When the mitogens concanavalin A (Con A) or phytohemagglutinin (PHA) were used to stimulate THC-treated splenocytes, a down-regulation of lymphocyte proliferation occurred, which reflected lower T-cell numbers in general and Ly2 positive cells specifically. When splenocytes were stimulated directly by using anti-CD3 antibody it was found that low concentrations of THC enhanced lymphocyte proliferation, T-cell numbers in general, and Ly2 cells specifically. These results emphasize that THC can either enhance or suppress aspects of the immune response, depending on the specific immune stimulants used and the specific parameter of immunity measured.

Enhanced growth restriction of Legionella pneumophila in endotoxin-treated macrophages

Macrophages from A/J mice are permissive for growth of Legionella pneumophila, an intracellular opportunistic pathogen that grows preferentially in macrophages. Macrophages from other mouse strains are highly resistant to growth of Legionella. In the present study, it was found that macrophages from A/J mice are readily activated by pretreatment with lipopolysaccharide (LPS), so that the cells do not permit Legionella to replicate in vitro, as occurs when untreated macrophages from A/J mice are cultured with these organisms for 48 hr. The augmentation of Legionella growth inhibition by LPS-activated macrophages from nonpermissive BDF1 mice also occurred. After in vitro infection, there was a 1000-fold increase in the number of Legionella in A/J macrophages and approximately a 10-fold increase in BDF1 macrophages, but LPS treatment of macrophages from either strain resulted in marked growth restrictions. This suppression was both dose dependent as well as dependent upon the time of addition of the LPS to the macrophages. Furthermore, the lipid A component of LPS was found to be as effective as the intact LPS in activating macrophages to inhibit the intracellular growth of Legionella. Further studies concerning the mechanisms involved are clearly warranted and in progress.

Cyclic AMP inhibition of lipopolysaccharide-induced restriction of Legionella pneumophila growth in macrophage cultures

The mechanism of the effects of lipopolysaccharide (LPS) on macrophages in terms of replication of intracellular facultative bacteria is unclear. It was found in the present study that the anti-Legionella pneumophila activity induced by LPS in macrophages from susceptible A/J mice was reversed in vitro by dibutyryl cyclic AMP (DcAMP). A 24-h pretreatment of murine thioglycolate-elicited macrophages with LPS resulted in an enhanced ability of these cells to inhibit the intracellular growth of L. pneumophila. This anti-L. pneumophila activity of macrophages induced by LPS was inhibited when DcAMP (10(-3) to 10(-5) M) was present during preincubation with LPS. The addition of DcAMP to the cultures was more effective before LPS treatment than after treatment. The effect of DcAMP was dose dependent. The secretion and production of acid phosphatase by LPS-activated macrophages were also inhibited by the addition of DcAMP before LPS treatment. Furthermore, the anti-L. pneumophila activity of macrophages induced by LPS could also be reversed in vitro by treatment with prostaglandin E2, colchicine, isoproterenol, theophylline, or hydrocortisone, all of which are known to increase the intracellular levels of cyclic AMP in various tissues. These observations indicate that the anti-L. pneumophila activity induced by LPS treatment can be modified by mechanisms involving cyclic nucleotide metabolism.

Alteration of rat splenocyte blastogenesis and interleukin-1 production following slow infusion of human tumor necrosis factor-alpha

The bolus injection of tumor necrosis factor (TNF)/cachectin into rats has been reported to induce shock and tissue injury similar to catabolic states seen in cachexia. In the present study, we administered TNF/cachectin to rats by either bolus injection or slow infusion and analyzed the influence on splenocyte mitogen-induced proliferation and interleukin-1 (IL-1) production. Also, TNF administration was compared with lipopolysaccharide (LPS) injection and saline injection. Serum TNF levels were elevated by 30 min following the start of slow infusion, peaked at around 90 min, and remained elevated throughout the 3-h sampling. However, analysis of serum TNF following a bolus injection showed that TNF peaked earlier (30 min) but then declined over the next 2.5 h. LPS infusion resulted in a serum TNF peak at 60-90 min with a rapid decline to near baseline by the end of the 3-h sampling. Spleens were removed from rats following either 3 h of infusion or 3 h following bolus injection, and single-cell suspensions were prepared and analyzed in culture for lymphocyte proliferation to either concanavalin-A (con-A) or pokeweed mitogen (PWM). Adherent spleen cell cultures were also tested for IL-1-forming capacity in response to LPS. The slow infusion of TNF had a suppressive effect on splenic T lymphocyte responsiveness to con-A. This suppressive effect was not observed in the response to the T cell-dependent B cell mitogen PWM.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential suppression of T-cell subpopulations by thc (delta-9-tetrahydrocannabinol)

THC (delta-9-tetrahydrocannabinol), the major psychoactive component of marijuana, has been shown to suppress various immune functions in vivo and in vitro. THC suppresses murine T-lymphocyte proliferation; however, the effects on T-cell subsets remain unclear. We have stimulated cultured murine splenocytes with the mitogens concanavalin A (Con A) or phytohemagglutinin (PHA) while exposing them to varying concentrations of THC. After three days, the cells were analyzed by the fluorescent activated cell sorter for the following T-cell markers--Thy1, L3T4 and Ly2. The Ly2 cells represent the suppressor/effector T-cells while L3T4 cells represent the helper T-cell subpopulations. The results show that the dose response suppressive effect of THC on T-cell proliferation reflects a preferential inhibition of Ly2 vs L3T4 cells. The effects of THC on other functional parameters are in the process of investigation.

Induction of interleukin 1 by Legionella pneumophila in murine peritoneal macrophage cultures

Legionella pneumophila-induced production of both membrane-associated and secreted interleukin 1 (mIL-1 and sIL-1, respectively) was examined utilizing peritoneal macrophages from BALB/c mice. The Legionella preparations for these studies included viable bacteria and formalin-killed whole cell preparations. Both of the preparations induced mIL-1 and sIL-1 in a dose-dependent fashion. However, the viable bacteria required about 1 log lower concentrations than the formalin-killed bacteria to induce the same level of IL-1 activity measured in the thymocyte proliferation assay. Kinetic studies showed that mIL-1 and sIL-1 were detectable within 4 hr after addition of either of the L. pneumophila preparations to the peritoneal macrophage cultures, with peak levels achieved within 24 hr. These results indicate that L. pneumophila is a potent inducer of both mIL-1 and sIL-1 in normal mouse peritoneal macrophage cultures.

Growth of Legionella pneumophila in thioglycolate-elicited peritoneal macrophages from A/J mice

Legionella pneumophila is a facultative intracellular bacterium which readily grows in cultures of guinea pig and human mononuclear phagocytes. In this report, we demonstrate that the Legionella sp. also grows in thioglycolate-elicited macrophages obtained from A/J mice but not in cells from other mouse strains tested, such as BDF1, DBA/2, C3H/HeN, C57BL/6, and BALB/c. Growth of Listeria monocytogenes and interleukin-1 production in A/J mice were similar to their growth and production in other strains tested, and the growth of Staphylococcus epidermidis was restricted by A/J macrophages. This finding suggests that although A/J macrophages share functional capabilities with cells from other mouse strains, they differ in growth restriction capacity for the Legionella sp. Resident macrophages were less permissive than were thioglycolate-elicited cells in that resident cells from A/J mice failed to support the growth of Legionella pneumophila. Also, resident cells from BDF1 mice rapidly eliminated the bacteria, rather than merely restricting growth. This finding was also observed in in vivo studies in which thioglycolate pretreatment of mice resulted in the enhanced recovery of viable bacteria from the peritoneal cavity of mice infected intraperitoneally. Higher numbers of bacteria were obtained from A/J mice and, in addition, this strain was more susceptible to the lethal effects of Legionella infection. These data suggest that, as with other intracellular bacteria, macrophages may serve a pivotal role in the early stages of Legionella infection and further suggest that the A/J mouse represents a useful animal model for the study of Legionella infection and immunity.

Induction of interleukin 1 by Legionella pneumophila antigens in mouse macrophage and human mononuclear leukocyte cultures

Exposure to Legionella pneumophila antigens has been reported to result in both an adjuvant effect and pathophysiological changes such as fever, headache, myalgia and arthralgias. Immunoenhancement and inflammatory changes have been associated with the production of interleukin 1, and we, therefore, sought an involvement of interleukin production in the alteration of biological responsiveness following exposure to Legionella pneumophila antigens. Killed Legionella pneumophila cells, incubated with mouse splenocytes, induced the formation of a soluble substance which enhanced splenocyte antibody production to heterologous antigen. The immunoenhancing substance was also produced by mouse peritoneal macrophages and supernatants from these cultures were demonstrated to also contain thymocyte co-mitogenic activity. Following gel filtration, this co-mitogenic activity eluted in the 15,000 molecular weight range suggesting an involvement of interleukin 1. Experiments with Legionella pneumophila cells, and cell extracts containing endotoxin, and purified endotoxin suggested that the interleukin 1 activity was induced by both endotoxin and non-endotoxin antigens. The Legionella pneumophila antigens were also found to be potent inducers of interleukin 1 activity in human peripheral blood mononuclear cell cultures. These results suggest that Legionella pneumophila antigens are potent inducers of interleukin 1 in both mouse and human cells. The induction of this monokine may partially account for both the immunoenhancing property of this bacterial species and the associated pathophysiological changes following infection with this microorganism.

Differential growth of Legionella pneumophila in guinea pig versus mouse macrophage cultures

Legionella pneumophila is a facultative intracellular bacterium which replicated well in inbred guinea pig strain 2 peritoneal macrophages at a low infectivity ratio. In contrast, the growth of this organism was markedly restricted in mouse (BDF1) peritoneal macrophages, even at a relatively high infectivity ratio. The initial uptake of L. pneumophila organisms by macrophages was similar in both animal species, and both groups of macrophages supported the growth of Listeria monocytogenes. Treatment of L. pneumophila with immune guinea pig serum did not result in restriction of bacterial growth in macrophages, but guinea pig macrophages were readily induced to suppress the growth of L. pneumophila by preincubation with supernatants obtained from mitogen-activated normal guinea pig splenocyte cultures. Thus, lymphokines generated from mitogen-stimulated guinea pig lymphocytes induced a restriction of growth of these organisms similar to that observed naturally with macrophages from mice, which are considered highly resistant to these bacteria. Although guinea pigs are considered highly susceptible to L. pneumophila infections and mice are considered relatively resistant, the mechanism of this difference is not clear. The results of the present study suggest that the restriction of L. pneumophila growth by macrophages relates to host susceptibility to infection and that cell populations permissive for L. pneumophila can be transformed to nonpermissive by products from stimulated lymphocytes but not by opsonization with immune serum.

Use of selective mesenteric vasodilator peptides in experimental nonocclusive mesenteric ischemia in the dog

Three structurally related peptides, ovine corticotropin-releasing factor, sauvagine, and urotensin I are selective mesenteric vasodilators in dogs. To assess the possible benefit of these peptides in nonocclusive mesenteric ischemia, they were compared with a nonselective vasodilator, sodium nitroprusside, in the anesthetized dog. Mesenteric blood flow was reduced by approximately 30%, without lowering of systemic arterial pressure, by either digoxin or pericardial tamponade. In the digoxin model, i.v. infusions of corticotropin-releasing factor, sauvagine, and urotensin I restored intestinal vascular resistance and mesenteric blood flow to control values, without causing a fall in systemic arterial blood pressure. In the tamponade model, only urotensin I was assessed, and it produced the same restoration of hemodynamic variables. On the other hand, in both models, i.v. infusions of nitroprusside, which were effective in correcting intestinal vascular resistance, produced a fall in arterial blood pressure (presumably because of systemic dilatation), which prevented restoration of mesenteric blood flow. Intestinal oxygen uptake was not altered by tamponade, but was reduced by 23% in the digoxin model, where it was restored to control values by both the peptides and nitroprusside. The increased oxygen extraction seen in both models was corrected by the peptides but not by nitroprusside, suggesting that nitroprusside may have a direct and offsetting metabolic effect on the gut.

Individual Xenopus histone genes are replication-independent in oocytes and replication-dependent in Xenopus or mouse somatic cells

We have assessed the response of many histone H3 mRNAs and an H1C mRNA in Xenopus tissue culture cells after treatment with the DNA synthesis inhibitor hydroxyurea. The amount of the histone mRNAs falls rapidly in response to the inhibitor. This response is prevented by cycloheximide. Cloned Xenopus histone genes were transfected into mouse cells and a cell line was obtained in which the Xenopus genes were actively expressed giving rise to mRNA with correct 5'-termini. The Xenopus genes were correctly regulated at the level of mRNA amounts in the mouse cell line. Nuclear microinjection experiments with Xenopus oocytes and S1 nuclease analysis of normal ovary RNA showed that the H1C gene, and probably also two H3 genes, which are replication-dependent in somatic cells are expressed in oocytes and are therefore replication-independent in this cell type. The same promoters are used in both replication-dependent and independent expression.

The effect of delta-9-tetrahydrocannabinol and 11-hydroxy-delta-9-tetrahydrocannabinol on T-lymphocyte and B-lymphocyte mitogen responses

Previous studies have shown that delta-9-tetrahydrocannabinol (THC) suppresses T-lymphocyte proliferation when added to human cell cultures. We report that THC when added to mouse splenocyte cultures suppressed T-lymphocyte (Con A, PHA) and B-lymphocyte (LPS) mitogen-induced proliferation. Although the ED50 concentrations (5 micrograms/ml; 1.6 X 10(-5)M) of THC were similar for suppressing all three mitogen responses, higher threshold concentrations of drug were required to effect suppression of the T-lymphocyte mitogen responses. Complete suppression of T- and B-lymphocyte responses was achieved with THC concentrations (8 micrograms/ml or 2.6 X 10(-5)M) which were not directly toxic as judged by vital dye exclusion. The hydroxylated metabolite of THC, 11-hydroxy-THC, was observed to be much less potent in the inhibition of lymphocyte proliferation. However, as with the parent compound, B-lymphocyte responses appeared to be the most affected by the drug. Additional studies demonstrated that both T- and B-lymphocyte proliferation is rapidly suppressed following THC treatment, not affected by a 24 hr. pretreatment with THC, and not as readily suppressed by THC in cultures containing 20% serum. Thus, THC appears to inhibit both T- and B-lymphocyte proliferation with B-lymphocyte responses displaying greater inhibition at lower drug concentration. The 11-hydroxy metabolite is much less suppressive in this system than the parent compound.

The role of B cell differentiation factors and specific T cell help in the pathogenesis of primary hypogammaglobulinemia

We have examined the function of T and B cells from patients with late onset primary acquired hypogammaglobulinemia (PHG). T cells from these patients give effective help to normal B cells for antigen-dependent antibody synthesis. PHG mononuclear cells also synthesize normal quantities of B cell differentiation factors, which enhance IgG, IgM and antigen-dependent antibody synthesis by normal lymphocytes. While patient T cells appear to behave appropriately, the responsiveness of patient B cells is abnormal. Although they respond to differentiation factors with increased synthesis of IgM, overall levels are 10-50-fold lower than normal B cells, and they produce little or no IgG. This pattern of response is not altered if normal T cells are the source of help. The poor response of the B cell appears to represent immaturity rather than an inherent defect, as IgG-secreting clones can be obtained after Epstein-Barr virus transformation of lymphocytes from certain patients, and some of these clones respond to differentiation factors with increased IgG production. The lack of any functional defect in the T population, and the apparent immaturity rather than abnormality of the B cells, may implicate accessory cells in the pathogenesis of the disease.

Corticotropin releasing factor-like peptides produce selective dilatation of the dog mesenteric circulation

Three synthetic peptides, ovine corticotropin-releasing factor, sauvagine, and urotensin I, contain homologous amino acid residues. In the anesthetized dog, all three produce marked and selective dilatation of the mesenteric circulation; none of the peptides influenced blood flow in the renal, femoral, carotid, or even celiac arteries. The mesenteric vasodilatation appeared to be unrelated to the common ability of these peptides to release corticotropin and beta-endorphin, and cannot be abolished or attenuated by conventional blocking agents or inhibitors. The unique action of these peptides suggests that there may be a related peptide in the intestine that acts to regulate intestinal blood flow. The peptides may also prove useful therapeutically in nonocclusive ischemia, if this unusual action is also present in humans.

Production of antibody by human B cells under serum-free conditions

A method is described for growing human B cells in 20 microliter hanging drops in Terasaki plates under serum-free conditions. B cell proliferation and differentiation has a critical dependence for added soybean lipid, while T cell proliferation does not. In this medium, pokeweed mitogen stimulation of separated human B cells induces high levels of immunoglobulin in a T dependent manner. Cells from donors vaccinated with tetanus toxoid and shown to be responders by a conventional culture system, produce high levels of IgG anti-tetanus antibody after antigen stimulation in these serum-free microcultures. The serum free culture system has the novel features of high sensitivity to dose of mitogen or antigen, low background responses and high antibody production with low cell numbers.

The interaction of specific T-cell help and non-specific B-cell growth factors in the production of anti-tetanus antibody by human B cells grown in serum-free microcultures

Apart from a brief period after in-vivo immunization, only a minority of human donors provide peripheral lymphocytes that synthesize specific antibody on stimulation with tetanus toxoid in vitro. A 20 microliters hanging drop microculture technique using serum-free medium has been adapted to analyse the conditions under which B cells mature into antibody-secreting cells. Multiple permutations of antigen dose, cell concentration and T:B cell ratios have been examined. The results indicate that in-vitro failure of antigen response by the majority of donors is not due simply to an inappropriate choice of culture conditions. The addition to antigen-stimulated cultures of a lectin-free conditioned medium derived from pokeweed mitogen-stimulated peripheral lymphocytes, enables B cells from the majority of donors to produce high titres of specific antibody, in a T-dependent manner, for up to 24 months after immunization. The observed failure of prolonged antigen responsiveness in vitro thus appears to represent a failure to expand a population of antigen-specific B cells, rather than indicating an absence of such clones.

Organization and expression of cloned histone gene clusters from Xenopus laevis and X. borealis

We have isolated several clones containing Xenopus histone genes from genomic libraries of X. laevis and X. borealis DNA. Each genomic clone has been mapped and the positions of 26 histone genes in seven laevis clones and 5 histone genes in one borealis clone have been determined. In laevis, the histone gene clusters show considerable variation in gene order within a single individual. When the cloned DNAs were microinjected into the nucleus of Xenopus oocytes, expression of cloned genes at the transcriptional and translational level was readily detectable. Previously unknown histone variants were revealed by the microinjection experiments.

Bactericidal activity of serum for Klebsiella rhinoscleromatis: studies on serum from a patient with rhinoscleroma and sera deficient in antibody or complement

The in-vitro bactericidal effect of serum for Klebsiella rhinoscleromatis was tested. Experiments with C2-deficient and hypogammaglobulinaemic human sera suggested that killing depended on activation of the classical complement pathway, although the alternative pathway probably amplified the effect. Serum from a patient with active rhinoscleroma, and another cured of the disease, showed normal killing.

Simple hanging drop (20 microliter) double antibody radioimmunoassay of human IgM, IgG, IgA, IgD and IgE

A simple hanging drop radioimmunoassay has been developed for different classes of human immunoglobulin from serum and culture supernatant samples. The immune precipitate was formed in inverted Terasaki plates (20 microliter per well) using 4 aliquots (5 microliter) as follows: (A) a standard or unknown sample; (B) rabbit antisera to the appropriate immunoglobulin class; (C) 125I-labelled human immunoglobulin of the appropriate class; (D) a developing goat-anti rabbit serum. The immune precipitate in the hanging drop was harvested and washed without centrifugation with a simple Terasaki plate harvester. The method gives a great saving both in time and in sample and reagent volumes in comparison with an established double antibody assay in tubes (4 X 100 microliter aliquots).

Cellular immunity in primary hypogammaglobulinaemia: evidence for a generalised lymphocyte defect in some patients with "common" variable hypogammaglobulinaemia

In vivo and in vitro T lymphocyte function was studied in 64 patients with X-linked and common "variable" primary hypogammaglobulinaemia. Lymphopenia, splenomegaly, depressed in vitro lymphocyte transformation to mitogens and failure to manifest delayed hypersensitivity skin reactions occurred frequently in the common "variable" group, particularly those with adult onset disease. However, relative circulating T lymphocyte numbers and in vitro lymphocyte transformation in a mixed lymphocyte reaction with the CLA4 lymphoid cell line were normal. Antibody mediated and PHA induced lymphocytotoxicity were also normal. These findings indicate the presence of a generalised lymphocyte defect which is selective for certain T lymphocyte functions. Despite these apparent T lymphocyte defect, none of the patients suffered from the unusual opportunistic parasitic, viral or fungal infections which tend to occur in infants with severe primary defects of both T and B lymphocytes.

Phosphorylation of deoxyguanosine by B and T lymphocytes: evidence against selective trapping of deoxyguanosine by T lymphocytes in purine nucleoside phosphorylase deficiency

T and B lymphocytes from blood and tonsils, as well as T and B lymphoid cell lines, phosphorylate deoxyguanosine which is probably the major toxic metabolite in purine nucleoside phosphorylase (PNP) deficiency. T and B cells also have similar activities of purine nucleoside phosphorylase. These findings indicate that the selective T cell defect in patients with PNP deficiency is unlikely to be due to a selective 'trapping' of deoxyguanosine by T lymphocytes.