Chronic imipramine treatment induces downregulation of alpha-2 receptors in rat's locus coeruleus and A2 region of the tractus solitarius

Imipramine is an effective antidepressant agent that blocks the reuptake of monoamines. In order to understand some of its basic mechanisms of action, we investigated the effects of chronic imipramine administration (10 mg/kg, i.p.; 21 days) on the alpha-2 receptor population of several brain sites. Alpha-2 receptor density was estimated by in vitro autoradiography using [3H]Idazoxan. The densitometric analysis revealed a decreased receptor density in the A2 region of the tractus solitarius (20%) and locus coeruleus (16%). No changes were observed in the amygdala, pyriform cortex, periacueductal gray and the bed nucleus of the stria terminalis. These results suggest that chronic imipramine treatment selectively modulates the alpha-2 receptor population localized in the brain stem norepinephrine-rich nuclei and not in the population present on limbic structures innervated by noradrenergic terminal projections. The possible physiological consequences of this selective modulation of alpha-2 receptors are discussed.

dlk, pG2 and Pref-1 mRNAs encode similar proteins belonging to the EGF-like superfamily. Identification of polymorphic variants of this RNA

dlk encodes a transmembrane protein member of the EGF-like family of homeotic proteins. dlk is expressed in the same type of neuroendocrine tissues and tumors as pG2, a gene cloned because of its differential expression in human pheochromocytomas versus neuroblastomas. Human dlk and pG2 cDNAs are around 98% similar in sequence, but the predicted proteins encoded by those genes are apparently unrelated. This fact suggested the existence of polymorphic variants of the same gene. We have sequenced again several pG2 and dlk clones in parallel. We identified a pG2 cDNA species corresponding to an alternatively spliced dlk mRNA, as well as several other variant forms of dlk mRNA. One of the pG2 clones resulted to be identical to human dlk and encode the same EGF-like protein. Pref-1, a cDNA isolated from 3T3-L1 fibroblasts, encodes a putative protein possessing an extracellular EGF-like domain similar to dlk, but a different intracellular region. Analysis of sequence data from different clones obtained in our laboratory confirmed some of the differences between dlk and Pref-1. However, the putative difference in the intracellular regions of dlk and Pref-1 was due to sequence artifacts. These data suggest that dlk, pG2 and Pref-1 are variant products of the same gene.

Automating the sleep laboratory: implementation and validation of digital recording and analysis

OBJECTIVES

We report on the implementation of digital processing in a large clinical and research sleep laboratory. The system includes the digital collection, display, analysis, and repository of physiological signals collected during sleep.

METHODS

After describing the original analog system, the computer equipment and software necessary for the digital implementation are presented and we explain our algorithms for rapid eye movement (REM) and delta-wave detection. Finally, we describe an experiment validating the digital system of display and analyses.

CONCLUSIONS

The digital processing of sleep signals saves computer operator, polysomnographic technologist, and computer time. It also saves resources such as polysomnographic paper and FM tape. The digital signals lend themselves to a large array of analysis techniques and result in improved signal quality. Automated REM and delta-wave detection via digital processing correlate highly with visual counts of rapid eye movements and delta waves.

Synthetic peptides representing T-cell epitopes act as carriers in pneumococcal polysaccharide conjugate vaccines

Improvement of antibody responses to polysaccharides through their linkage to proteins is thought to be mediated by protein-specific T helper (Th) cells. To investigate whether the carrier protein of a conjugate could be substituted by a Th epitope, Streptococcus pneumoniae type 17F polysaccharide (PS) was bromoacetylated and coupled to different peptides via their carboxy-terminal cysteines. Two peptides, one from the mycobacterial 65-kDa heat shock protein (hsp65) and the other from influenza virus hemagglutinin, are well-known Th epitopes. Two other peptides were selected from the pneumolysin sequence by Th epitope prediction methods; one of them was synthesized with cysteine either at the carboxy or the amino terminus. Three conjugates consistently elicited in mice anti-PS immunoglobulin M (IgM) and IgG responses that were not observed upon immunization with derivatized PS without peptide. The same conjugates induced no anti-PS antibody responses in athymic (nu/nu) mice, whereas clear responses were elicited in euthymic (nu/+) controls, demonstrating the thymus-dependent character of these conjugates. Only the three conjugates inducing anti-PS responses were capable of eliciting antipeptide antibodies. One of the immunogenic conjugates was studied in more detail. It induced significant protection and an anti-PS IgG response comprising all subclasses. On the basis of these results and proliferation studies with peptide and conjugate-primed cells, it is concluded that linkage of Th epitopes to PS in the right orientation enhances its immunogenicity in a thymus-dependent manner. Future possibilities for using peptides as carriers for inducing antibody responses to poorly immunogenic saccharide antigens are discussed.

A deletion mutant of the LMP1 oncogene of Epstein-Barr virus is associated with evolution of angioimmunoblastic lymphadenopathy into B immunoblastic lymphoma

The latent membrane protein 1 (LMP1) oncogene is one of the major proteins synthesized by the Epstein-Barr virus (EBV). It is expressed in Reed-Sternberg cells of Hodgkin's disease (HD), tumor cells of nasopharyngeal carcinoma (NPC), and immunoblasts of angioimmunoblastic lymphadenopathy (AILD). A particular LMP1 deletion mutant was recently identified in NPC and clinically and histologically aggressive HD. We studied two patients with AILD that subsequently progressed into immunoblastic lymphoma (IBL) in order to investigate whether the LMP1 deletion mutant was implicated in progression of AILD into IBL. Immunohistology and in situ hybridization were performed on diagnostic biopsies. DNA extracted from fresh frozen material was used for rearrangement studies and polymerase chain reaction (PCR) based amplification and sequencing of portions of the LMP1 gene. Immunohistochemistry revealed B cell origin of both cases of IBL. In the first patient clonal rearrangement of the immunoglobulin heavy-chain gene was present in IBL but not in AILD. In this patient, scattered immunoblasts of AILD and numerous tumor cells of B-IBL were shown to contain EBV transcripts (EBER1) and to express LMP1. Sequence analysis of the LMP1 gene from AILD and IBL in the first, and from IBL in the second patient, revealed identical deletions and point mutations. This LMP1 deletion mutant is identical to those which have been reported in HD and NPC. Its association with evolution of AILD into B-IBL, aggressive HD and NPC, suggests that this particular mutant is more widespread than originally thought and is clinically relevant.

Carrier-mediated electrogenic transport of estradiol-17 beta-glucuronide in rat liver BMV

Estradiol-17 beta-glucuronide (E(2)17G) is one of a series of naturally occurring glucuronide conjugates of the steroid D-ring that induce cholestasis in the rat and nonhuman primate. The present studies characterized the transport of [3H]E(2)17G in basolateral membrane vesicles (BMVs) from male rat liver. The uptake of E(2)17G was temperature dependent, occurred into an osmotically sensitive space, and was saturable, with an apparent Michaelis constant and maximal velocity of 13 microM and 29 pmol.mg protein-1.5 s-1, respectively. Uptake was not coupled to the uptake of Na+ nor to Cl-or OH- exchange but was markedly stimulated by an inside-positive membrane potential. Bromosulfophthalein inhibited the uptake of E217G noncompetitively; estriol-16 alpha-glucuronide, but not estradiol-3-glucuronide or estradiol-3-SO4-17 beta-glucuronide, inhibited the uptake of E(2)17G. Thus E(2)17G is transported as an anion by facilitated diffusion by a system that differs from the multispecific Na(+)-taurocholate cotransport system and the bromosulfophthalein transport system.

Murine splenic hematopoietic subpopulations: the enlarged undifferentiated subset in New Zealand black mice is multipotent stem cells

We recently reported that a significant population of the murine splenic non-T, non-B "null" cell compartment consists of non-lineage-specific, undifferentiated cells which are in the G0 and G1 phases of the cell cycle and that their numbers are particularly high in the spleens of New Zealand Black mice. A highly enriched population of these non-lineage-specific cells obtained by successive elimination of differentiated cells was further purified to homogeneity by fluorescence-activated cell sorting. The morphologic, phenotypic, and histochemical characteristics of this purified population suggest that these cells may be primitive hematopoietic stem cells. The germ line configuration of the genomic DNA establishes that these are uncommitted stem cells. In vivo, these cells form day 12 colonies in the spleen and liver of lethally irradiated recipients and confer radioprotection. These cells also differentiate into T- and B-cell lineages and reconstitute the immunodeficiency in mice with severe combined immunodeficiency. In response to a combination of a very few early-acting lymphokines and/or stromal cell-conditioned medium in vitro, these cells differentiate into both myeloid and lymphoid cell types. More of these cells are obtained from the enlarged spleens of New Zealand Black mice than from those of BALB/c mice. The presence of a comparatively higher number of stem cells in the spleen than in the marrow or fetal liver provides an alternative, and possibly superior, source of uncommitted stem cells for a variety of experimental investigations or therapeutic manipulations.

17 beta-estradiol glucuronide: an inducer of cholestasis and a physiological substrate for the multidrug resistance transporter

The multidrug resistance (MDR) gene family has been shown to be highly expressed in several normal tissues including the canalicular membrane of the hepatocyte. We report that a cholestatic estrogen metabolite, 17 beta-estradiol glucuronide (E217G), is a substrate for the MDR transporter, P-glycoprotein. In cytotoxicity studies, the MDR sarcoma cell line Dx5 was 4.7-fold resistant to E217G, and the K562/R7 leukemia MDR cell line was 5.0-fold resistant to E217G relative to their parental cell lines. There was also a 2- to 3-fold accumulation defect of [3H]E217G in the MDR cells relative to their parental cell lines. E217G (100 microM) modulated resistance ot doxorubicin, taxol, vinblastine, and etoposide in the Dx5 cells, completely reversing the 30- to 60-fold resistance observed with these agents. E217G had no effect on the toxicity of these compounds in the parental cell line (MES-SA). In contrast, MDR cells were not resistant to the noncholestatic estrogen metabolite, estriol 3-glucuronide, and this metabolite did not modulate resistance to MDR substrates. ATP-dependent transport of [3H]E217G in rat canalicular membranes was inhibited by several MDR substrates including vinblastine, etoposide, verapamil, cyclosporine, and PSC-833.

Effects of serine protease inhibitor, TAME, on IL-1 beta in LPS-stimulated human monocytes: relationship between synthesis and release of a 33-kDa precursor and the 17-kDa biologically active species

LPS stimulation of human monocytes in vitro induced release of the 17-kDa mature IL-1 beta (mIL-1 beta) but did not result in release of precursor IL-1 beta (pIL-1 beta). In contrast, the presence of a serine protease inhibitor, N alpha-(p-toluene sulfonyl)-L-arginine methyl ester (TAME; 10 mM) for 6 or 18 h was associated with the LPS-stimulated release of the 33-kDa pIL-1 beta as well. These effects were initially discerned from observations that the fraction of the total IL-1 beta produced (as detected by ELISA) that was released from monocytes increased in the presence of TAME, and immunoblot assays confirmed that this fraction was predominantly 33-kDa IL-1 beta. A global decrease in monocyte protein synthesis was also observed after prolonged (18-h) exposure to TAME and was associated with a decrease in IL-1 beta synthesis, predominantly affecting 31-kDa pIL-1 beta, and a dose-dependent inhibition of TNF-alpha production. Parallel examination of lactate dehydrogenase (LDH) release indicated that pIL-1 beta release was unrelated to cell lysis. These results demonstrate that TAME-inhibitable serine proteases are probably involved in the production and eventual proteolysis of the 33-kDa pIL-1 beta in situ but are probably not mechanistically related to either maturation of the IL-1 beta molecule or signaling of IL-1 beta release. IL-1 beta release appears to be dependent on the amount of total IL-1 beta synthesized. Serine proteolysis may constitute a degradative pathway for excess precursor, which, if interfered with, could result in release of the higher-molecular-weight forms of IL-1 beta.

Tissue and organ procurement in the emergency department setting

A retrospective chart review of all emergency department (ED) deaths in patients younger than 65 years in seven area hospitals was performed for the calendar year of 1990. The number and percentage of families approached and consenting to tissue donation among the various EDs was compared and reasons for not approaching families were evaluated for their validity. Procurement rates between the years 1990 and 1991 were compared for two area hospitals, which made a specified (nonmedical) service responsible for tissue requests in 1991. There were 368 deaths, 255 of which were potential donors by acceptable criteria. Only 109 (43%) families were approached regarding tissue donation. The overall procurement rate was 12%. Suburban EDs had a higher approach and procurement rate than did urban EDs (49% vs 36%; P < .05 and 19% vs 5%; P < .01, respectively). Procurement rates for two hospitals that designated a specific procurement service in 1991 more than doubled (5% vs 11%; P = NS). Tissue procurement rates in EDs with procurement systems in place are low despite consent rates of those approached of 36%. The major contributing factor is the failure to request tissue from the families of eligible candidates even when there are no exclusion criteria met. Suburban EDs had a higher success rate than urban EDs.

Lipopolysaccharide from Brucella abortus behaves as a T-cell-independent type 1 carrier in murine antigen-specific antibody responses

In order to determine the carrier nature of lipopolysaccharide from Brucella abortus (LPS-BA) in evoking humoral responses, normal and immunodeficient mice were immunized with trinitrophenyl (TNP)-conjugated LPS-BA (TNP-LPS-BA) and the responses were compared with those to known T-dependent and T-independent antigens. TNP-LPS-BA, like T-independent type 1 (TI-1) antigens such as TNP-BA and TNP-LPS from Escherichia coli (TNP-LPS-EC), generated anti-TNP responses in BALB/c, athymic BALB/c nu/nu, and CBA/N mice. In contrast, N-2,4-dinitrophenyl-beta-alanylglycylglycyl-substituted keyhole limpet hemocyanin, a typical T-dependent antigen, was not immunogenic in athymic mice, and TNP-Ficoll (T-independent type 2) was ineffective in eliciting humoral responses in CBA/N mice. These results indicate that LPS from B. abortus acts as a TI-1 carrier in generating antibody responses. In C3H/HeJ mice, TNP-LPS-BA generated higher-titer immunoglobulin G1 (IgG1), IgG2a, and IgG2b anti-TNP antibodies than TNP-LPS-EC. Compared with those from BALB/c mice, pure resting B cells isolated from C3H/HeJ mice exhibited a 30-fold lower proliferative response to LPS-EC, whereas the LPS-BA response was reduced to a lesser extent (5-fold). This suggests that the disparity observed in antibody titers was due to different abilities of LPS from B. abortus and E. coli to stimulate C3H/HeJ B cells. The ability of LPS from B. abortus to act as a carrier in generating humoral immune responses indicates that LPS-BA can be substituted for whole B. abortus organisms in vaccine development.

dlk, a putative mammalian homeotic gene differentially expressed in small cell lung carcinoma and neuroendocrine tumor cell line

Gastrin releasing peptide is mitogenic for mouse Swiss 3T3 fibroblasts and certain human small cell lung carcinoma (SCLC) cells but not for mouse Balb/c 3T3 fibroblasts. To identify new molecules associated with the gastrin releasing peptide-responsive phenotype, clones isolated from a differential cDNA library between Swiss and Balb/c 3T3 fibroblasts were used to screen for their expression in human SCLC cell lines. Using this approach, we have isolated and characterized human and mouse cDNA clones encoding a novel protein. This protein is a putative transmembrane protein belonging to the epidermal growth factor-like superfamily. In vitro transcription and translation studies detect a 42-kDa protein, in agreement with the size predicted from the translated cDNA sequence. This protein (termed Delta-like or dlk) is highly homologous to invertebrate homeotic proteins, including Delta, and Notch, the products of neurogenic loci involved in normal neural differentiation in Drosophila. dlk is expressed in tumors with neuroendocrine features, such as neuroblastoma, pheochromocytoma, and a subset of SCLC cell lines. However, its expression in normal tissues is restricted to the adrenal gland and placenta. These data suggest that dlk may be involved in neuroendocrine differentiation and, because of its cellular location and restricted expression in normal tissues, it may be a potential therapeutic target in neuroendocrine tumors, particularly SCLC.

Production and release of IL-1 beta by human peripheral blood monocytes in response to diverse stimuli: possible role of "microdamage" to account for unregulated release

Three different stimuli [lipopolysaccharide (LPS), concanavalin A (Con A), and phorbol myristate acetate (PMA)] all induced production and release of interleukin-1 beta (IL-1 beta) from human monocytes in vitro. Of the three, LPS demonstrated the greatest potency for IL-1 beta production. LPS and Con A demonstrated similar efficacy with respect to IL-1 beta release. LPS was approximately 1000 times more potent than Con A in this regard. LPS- and Con A-induced IL-1 beta release occurred within 3 h and 12-24 h, respectively. Challenge with PMA induced low levels of IL-1 beta production with a relatively large percentage released. IL-1 beta release by all three stimuli occurred at concentrations greater than or equal to those required for optimal IL-1 beta production. The amount of IL-1 beta released correlated with total IL-1 beta produced and was associated with release of lactate dehydrogenase (LDH), a cytosolic enzyme marker used to evaluate cell membrane integrity. IL-1 beta release preceded LDH release temporally. LPS and Con A had no effect on total cell protein synthesis, a measure of overt toxicity, while PMA inhibited protein synthesis in a dose-dependent fashion. LPS and Con A both induced expression of a 33- and 29-kDa precursor IL-1 beta, but only the 17-kDa form was released. These data suggest that IL-1 beta is released by a process different from regulated secretion. While PMA induces a more profound damage, LPS and Con A may stimulate release of IL-1 beta from human monocytes in vitro through induction of microdamage to the cell membrane.

CD3-induced preferential hydrolysis of polyphosphoinositides and calcium regulation of inositol phosphate metabolism in a permeabilized murine T cell clone

Murine T helper cloned cells permeabilized with the bacterial lysin, tetanolysin, were used to investigate the role of intracellular Ca2+ in regulating myo-[2-3H] inositol phospholipid (InsPL) hydrolysis triggered upon perturbation of the T cell receptor-CD3 complex. [Ca2+] was controlled by a calcium/magnesium/EGTA buffer. Antibody (mAb) aggregation of CD3 induced InsPL hydrolysis in the absence of added Ca2+. However, stimulated InsPL hydrolysis increased with the free [Ca2+], reaching a maximum at 100-300 nM [Ca2+]. Ca2+ increased the overall efficiency of hydrolysis without changes in EC50 of the anti-CD3 mAb. The response diminished at > 300 nM [Ca2+] due to a mixed type inhibition. Ca2+ alone had no effect on inositol phosphate levels. Polyphosphoinositides were preferentially cleaved, since no accumulation of Ins(1)P/Ins(3)P was detected, indicating that direct hydrolysis of phosphatidylinositol did not occur, irrespective of the Ca2+ concentration. [Ca2+] above 300 nM shifted the relative amounts of CD3-induced inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) in favor of the latter. Unlabeled permeabilized cells exposed to > or = 100 nM [Ca2+] showed enhanced conversion of [3H]Ins(1,4,5)P3 to [3H]Ins(1,3,4,5)P4. In conclusion, InsPL hydrolysis is optimally triggered by CD3 perturbation at intracellular Ca2+ levels approximating those observed in intact resting lymphocytes (100 nM). Ca2+ concentrations similar to those triggered by InsPL-derived metabolites may inhibit InsPL hydrolysis and promote Ins(1,3,4,5)P4 production, thus controlling the amounts of Ins(1,4,5)P3.

Stimulation of human monocytes by anti-CD3 monoclonal antibody: induction of inflammatory mediator release via immobilization of Fc receptor by adsorbed immunoglobulin and T-lymphocytes

Human monocytes released superoxide anion, prostaglandin E2, leukotriene B4, IL-1, and TNF when exposed to plastic surfaces coated with murine anti-CD3 monoclonal antibody, OKT 3. Stimulation of mediator release by OKT 3 was dependent on the amount of antibody immobilized onto wells of plastic tissue culture plates. Soluble antibody or antibody adsorbed to monocytes and reacted with an aggregating ("cross-linking") second antibody failed to induce mediator release. Monocytes "armed" with OKT 3 formed rosettes with T cells in a fashion indistinguishable from that seen between monocytes and T cells sensitized with OKT 3. Monocytes with adsorbed OKT 3 antibodies released IL-1 beta and TNF-alpha when exposed to unsensitized T cells, although increased superoxide release could not be detected. OKT 4a, a murine IgG2a antibody that reacts with a different T cell epitope (CD4), failed to induce cytokine release from monocytes when cross-linked by T cells or a CD4+ T cell line, even in the presence of IL-2 or IFN-gamma. These data indicate that certain antibodies bound to Fc receptors (FcR) of monocytes may trigger monocyte function when reacting with cells bearing the appropriate target antigens. FcR-mediated signaling resulting in mediator release may be involved in initiating or regulating the immune response. Furthermore, systemically administered monoclonal antibodies may induce inflammatory responses and their attendant symptomatologies via their interaction with FcR-bearing inflammatory cells.

Microfilament assembly modulates phospholipase C-mediated signal transduction by the TCR/CD3 in murine T helper lymphocytes

Cytoskeletal involvement in the response to TCR/CD3 ligation and in signal transduction was investigated in a murine Th cell type 2 clone. Cells coated with the hamster anti-CD3 mAb, 145-2C11 (2C11 mAb), and exposed to goat anti-hamster demonstrated an increase in polymerized actin as well as an increase in inositol phospholipid hydrolysis mediated by activation of phospholipase C. Pretreatment with cytochalasins (Cyt) (D or B), drugs that interact with cellular actin, prevented actin polymerization, and augmented the initial rate and total amount of inositol phosphates produced. Drugs modifying microtubule function were ineffective. The intracellular Ca2+ rise attributed to InsP3 and InsP4 generated in response to CD3 perturbation was augmented by CytD. CytD treatment did not affect inositol phosphate generation resulting from the stimulation of guanine nucleotide-binding proteins with aluminium tetrafluoride, indicating that the action of CytD was specific for receptor-mediated inositol phospholipids. CytD decreased the rate of anti-CD3-induced receptor internalization. These data suggest that the assembly of microfilaments plays a role in CD3 internalization and that a CytD-sensitive mechanism uncouples the TCR/CD3 complex from phospholipase C-mediated signaling.

Microfilament assembly modulates phospholipase C-mediated signal transduction by the TCR/CD3 in murine T helper lymphocytes

Cytoskeletal involvement in the response to TCR/CD3 ligation and in signal transduction was investigated in a murine Th cell type 2 clone. Cells coated with the hamster anti-CD3 mAb, 145-2C11 (2C11 mAb), and exposed to goat anti-hamster demonstrated an increase in polymerized actin as well as an increase in inositol phospholipid hydrolysis mediated by activation of phospholipase C. Pretreatment with cytochalasins (Cyt) (D or B), drugs that interact with cellular actin, prevented actin polymerization, and augmented the initial rate and total amount of inositol phosphates produced. Drugs modifying microtubule function were ineffective. The intracellular Ca2+ rise attributed to InsP3 and InsP4 generated in response to CD3 perturbation was augmented by CytD. CytD treatment did not affect inositol phosphate generation resulting from the stimulation of guanine nucleotide-binding proteins with aluminium tetrafluoride, indicating that the action of CytD was specific for receptor-mediated inositol phospholipids. CytD decreased the rate of anti-CD3-induced receptor internalization. These data suggest that the assembly of microfilaments plays a role in CD3 internalization and that a CytD-sensitive mechanism uncouples the TCR/CD3 complex from phospholipase C-mediated signaling.

Differential turnover of enzymes involved in human monocyte eicosanoid metabolism. Selective inhibition of cyclooxygenase product formation by cycloheximide in the absence of effects on 5-lipoxygenase or phospholipase A2

Human monocytes treated with cycloheximide (CHX) demonstrated a concentration- and time-dependent inhibition of prostaglandin E2 (PGE2) synthesis and release in response to stimulation with phorbol myristate acetate, ionomycin, serum-treated zymosan, or concanavalin A. The effect of CHX required preincubation and was largely reversible within 2 hr. Thromboxane A2 release was affected similarly but no comparable effects were observed on labeled arachidonic acid release or leukotriene B4 generation. The PGE2 response was also inhibited by CHX when monocytes were given exogenous arachidonic acid with or without stimulation. CHX pretreatment also comparably decreased the amount of immunoreactive cyclooxygenase in resting and stimulated monocytes. These data indicate that monocyte cyclooxygenase, in contrast to phospholipase A2 or 5-lipoxygenase and their regulatory proteins, turns over rapidly and may be a target for up- or down-regulation by pharmacologic or (potentially) physiologic agents which affect protein synthesis or degradation.

Inflammatory mediator release from human monocytes via immobilized Fc receptors. Its potential role in adverse reactions to systemic monoclonal antibody therapy

Human monocytes released superoxide anion, IL-1, and TNF subsequent to binding of their Fc receptor I to murine IgG2a or rabbit IgG. Fc receptor II binding to murine IgG2b or IgG1 had similar consequences. Immobilized murine monoclonal antibodies, IgG2a anti-CD3 (OKT3) or IgG1 anti-CD44 also induced superoxide anion and monokine production. Monocytes bound OKT3 via FcRI and responded to immobilized OKT3 by inflammatory mediator release in the absence of T cells. These results suggest that direct interaction of immunoglobulins with monocytes via FcR may represent an important phase of the pathophysiology of adverse reactions to systemic monoclonal antibodies.

Increased intracellular cyclic AMP inhibits inositol phospholipid hydrolysis induced by perturbation of the T cell receptor/CD3 complex but not by G-protein stimulation. Association with protein kinase A-mediated phosphorylation of phospholipase C-gamma 1

Modulation of inositol phospholipid (InsPL) hydrolysis in response to increasing intracellular concentrations of cyclic AMP (cAMP) was studied in a murine T helper type II (Th2) lymphocyte clone, 8-5-5. Intact 8-5-5 cells produced maximal amounts of cAMP in response to prostaglandin E2 (PGE2), cholera toxin (CTx) or 7 beta-deacetyl-7 beta-(gamma-N-methylpiperazino)butyryl forskolin (dmpb-forskolin). cAMP generation reached a plateau after 5 min of treatment with dmpb-forskolin (300 microM) or PGE2 (1 microM), but required 60 min of treatment with CTx (1 microgram/ml). Preincubation of 8-5-5 cells with 1 microM-PGE2 or 300 microM-dmpb-forskolin (10 min at 37 degrees C) or with 1 microgram of CTx/ml (60 min at 37 degrees C) completely inhibited InsPL hydrolysis induced by perturbation of the T cell receptor (TCR)/CD3 complex with the monoclonal antibody 145.2C11. Preincubation with the cAMP analogue 8-bromo-cyclic AMP (8-Br-cAMP) also inhibited InsPL hydrolysis. Tetanolysin-permeabilized 8-5-5 cells produced cAMP in response to PGE2, dmpb-forskolin and guanosine 5'-[gamma-thio]triphosphate (GTP[S]), a non-cell-permeating, non-hydrolysable analogue of GTP that directly activates G-proteins. No inhibition of TCR/CD3-induced InsPL hydrolysis was observed under these conditions. InsPL hydrolysis was also unaffected when permeabilized cells were incubated with up to 10 mM-8-Br-cAMP, suggesting that permeabilized cells lost (a) soluble effector molecule(s) involved in mediating the inhibitory effect observed in intact cells. Treatment of 8-5-5 cells with dmpb-forskolin or CTx prior to permeabilization resulted in inhibition of TCR/CD3-induced InsPL hydrolysis, but did not affect InsPL hydrolysis induced via G-protein stimulation with GTP[S]. Treatment of permeabilized 8-5-5 cells with purified cAMP-dependent protein kinase (PKA) resulted in inhibition of TCR/CD3- but not GTP[S]-induced InsPL hydrolysis. This effect was associated with phosphorylation of phospholipase (PLC)-gamma 1 in the absence of phosphorylation of components of the TCR/CD3 complex. These results suggest that PKA-mediated phosphorylation of PLC may regulate TCR/CD3-induced InsPL hydrolysis.

Lipopolysaccharide (LPS) from Brucella abortus is less toxic than that from Escherichia coli, suggesting the possible use of B. abortus or LPS from B. abortus as a carrier in vaccines

Brucella abortus may be useful as a component of vaccines. This is because it possesses several unique properties as a carrier that enable it to stimulate human B cells even in the relative absence of T cells. Human immunodeficiency virus type 1 proteins conjugated to B. abortus could induce neutralizing antibodies against human immunodeficiency virus type 1. Recently we showed that the characteristics of lipopolysaccharide (LPS) derived from B. abortus are similar to those of the whole bacterium in that the LPS acts as a T-independent type 1 carrier in mice. In this study we wanted to determine whether LPS derived from B. abortus is associated with the adverse effects seen with other bacterial endotoxins. LPS purified from B. abortus by butanol extraction was shown to have less than 2% (wt/wt) contamination by protein and less than 1% (wt/wt) contamination by nucleic acids and to contain 1% (wt/wt) ketodeoxyoctanic acid. Compared with LPS derived from Escherichia coli, B. abortus LPS was 10,000-fold less potent in eliciting fever in rabbits, 268-fold less potent in killing D-galactosamine-sensitized mice, and 1,400-fold and 400-fold less potent in inducing interleukin-1 beta and tumor necrosis factor alpha production, respectively. These results suggest that B. abortus LPS is much less likely than the LPS from E. coli to evoke endotoxic shock; therefore, it may be feasible to incorporate B. abortus as a component of vaccines.