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PubMed1994

An aromatic effector specificity mutant of the transcriptional regulator DmpR overcomes the growth constraints of Pseudomonas sp. strain CF600 on para-substituted methylphenols.

The pVI150 catabolic plasmid of Pseudomonas sp. strain CF600 carries the dmp system, which comprises the divergently transcribed dmpR gene and the dmp operon coding for the catabolic enzymes required for growth on (methyl)phenols. The constitutively expressed DmpR transcriptional activator positively controls the expression of the RpoN-dependent dmp operon promoter in the presence of the aromatic effector in the growth medium. However, the magnitude of the transcriptional response differs depending on the position of the methyl substituent on the aromatic ring. Experiments involving an elevated copy number of the dmp system demonstrate that growth on para-substituted methylphenols is limited by the level of the catabolic enzymes. An effector specificity mutant of DmpR, DmpR-E135K, that responded to the presence of 4-ethylphenol, a noneffector of the wild-type protein, was isolated by genetic selection. The single point mutation in DmpR-E135K, which results in a Glu-to-Lys change in residue 135, also results in a regulator with enhanced recognition of para-substituted methylphenols. The DmpR-E135K mutation, when introduced into the wild-type strain, confers enhanced utilization of the para-substituted methylphenols. These experiments demonstrate that the aromatic effector activation of wild-type DmpR by the para-substituted methylphenols is a major factor limiting the catabolism of these compounds.

Bacterial Proteins↗
PubMed2001

Roles of LcrG and LcrV during type III targeting of effector Yops by Yersinia enterocolitica.

Yersinia enterocolitica target effector Yop proteins into the cytosol of eukaryotic cells by a mechanism requiring the type III machinery. LcrG and LcrV have been suggested to fulfill essential functions during the type III targeting of effector Yops. It is reported here that knockout mutations of lcrG caused mutant yersiniae to prematurely secrete Yops into the extracellular medium without abolishing the type III targeting mechanism (Los phenotype [loss of type III targeting specificity]). Knockout mutations in lcrV reduced type III targeting of mutant yersiniae but did not promote secretion into the extracellular medium (Not [no type III targeting]). However, knockout mutations in both genes caused DeltalcrGV yersiniae to display a Los phenotype similar to that of strains carrying knockout mutations in lcrG alone. LcrG binding to LcrV resulted in the formation of soluble LcrGV complexes in the bacterial cytoplasm. Membrane-associated, bacterial-surface-displayed or -secreted LcrG could not be detected. Most of LcrV was located in the bacterial cytoplasm; however, small amounts were secreted into the extracellular medium. These data support a model whereby LcrG may act as a negative regulator of type III targeting in the bacterial cytoplasm, an activity that is modulated by LcrG binding to LcrV. No support could be gathered for the hypothesis whereby LcrG and LcrV may act as a bacterial surface receptor for host cells, allowing effector Yop translocation across the eukaryotic plasma membrane.

Antigens, Bacterial↗
PubMed2002

Evidence for targeting of Yop effectors by the chromosomally encoded Ysa type III secretion system of Yersinia enterocolitica.

Yersinia enterocolitica O:8 has two contact-dependent type III secretion systems (TTSSs). The Ysa TTSS is encoded by a set of genes located on the chromosome and exports Ysp proteins. The Ysc TTSS and the Yop effector proteins it exports are encoded by genes located on plasmid pYVe8081. In this study, secretion of YspG, YspH, and YspJ by the Ysa TTSS was shown to require pYVe8081. Furthermore, mutations that blocked the function of the Ysc TTSS did not affect YspG, YspH, and YspJ production. This indicated that YspG, YspH, and YspJ are encoded by genes located on pYVe8081 and that they may correspond to Yops. A comparison of Ysps with Yop effectors secreted by Y. enterocolitica indicated that YspG, YspH, and YspJ have apparent molecular masses similar to those of YopN, YopP, and YopE, respectively. Immunoblot analysis demonstrated that antibodies directed against YopN, YopP, and YopE recognized YspG, YspH, and YspJ. Furthermore, mutations in yopN, yopP, and yopE specifically blocked YopN, YopP, and YopE secretion by the Ysc TTSS and YspG, YspH, and YspJ secretion by the Ysa TTSS. These results indicate YspG, YspH, and YspJ are actually YopN, YopP, and YopE. Additional analysis demonstrated that YopP and YspH secretion was restored to yopP mutants by complementation in trans with a wild-type copy of the yopP gene. Examination of Y. enterocolitica-infected J774A.1 macrophages revealed that both the Ysc and Ysa TTSSs contribute to YopP-dependent suppression of tumor necrosis factor alpha production. This indicates that both the Ysa and Ysc TTSSs are capable of targeting YopP and that they influence Y. enterocolitica interactions with macrophages. Taken together, these results suggest that the Ysa and Ysc TTSSs contribute to Y. enterocolitica virulence by exporting both unique and common subsets of effectors.

Animals↗
PubMed2004

Pseudomonas syringae type III secretion system targeting signals and novel effectors studied with a Cya translocation reporter.

Pseudomonas syringae pv. tomato strain DC3000 is a pathogen of tomato and Arabidopsis: The hrp-hrc-encoded type III secretion system (TTSS), which injects bacterial effector proteins (primarily called Hop or Avr proteins) into plant cells, is required for pathogenicity. In addition to being regulated by the HrpL alternative sigma factor, most avr or hop genes encode proteins with N termini that have several characteristic features, including (i) a high percentage of Ser residues, (ii) an aliphatic amino acid (Ile, Leu, or Val) or Pro at the third or fourth position, and (iii) a lack of negatively charged amino acids within the first 12 residues. Here, the well-studied effector AvrPto was used to optimize a calmodulin-dependent adenylate cyclase (Cya) reporter system for Hrp-mediated translocation of P. syringae TTSS effectors into plant cells. This system includes a cloned P. syringae hrp gene cluster and the model plant Nicotiana benthamiana. Analyses of truncated AvrPto proteins fused to Cya revealed that the N-terminal 16 amino acids and/or codons of AvrPto are sufficient to direct weak translocation into plant cells and that longer N-terminal fragments direct progressively stronger translocation. AvrB, tested because it is poorly secreted in cultures by the P. syringae Hrp system, was translocated into plant cells as effectively as AvrPto. The translocation of several DC3000 candidate Hop proteins was also examined by using Cya as a reporter, which led to identification of three new intact Hop proteins, designated HopPtoQ, HopPtoT1, and HopPtoV, as well as two truncated Hop proteins encoded by the naturally disrupted genes hopPtoS4::tnpA and hopPtoAG::tnpA. We also confirmed that HopPtoK, HopPtoC, and AvrPphE(Pto) are translocated into plant cells. These results increased the number of Hrp system-secreted proteins in DC3000 to 40. Although most of the newly identified Hop proteins possess N termini that have the same features as the N termini of previously described Hop proteins, HopPtoV has none of these characteristics. Our results indicate that Cya should be a useful reporter for exploring multiple aspects of the Hrp system in P. syringae.

Adenylyl Cyclases↗
PubMed2004

Effector-mediated interaction of CbbRI and CbbRII regulators with target sequences in Rhodobacter capsulatus.

In Rhodobacter capsulatus, genes encoding enzymes of the Calvin-Benson-Bassham reductive pentose phosphate pathway are located in the cbb(I) and cbb(II) operons. Each operon contains a divergently transcribed LysR-type transcriptional activator (CbbR(I) and CbbR(II)) that regulates the expression of its cognate cbb promoter in response to an as yet unidentified effector molecule(s). Both CbbR(I) and CbbR(II) were purified, and the ability of a variety of potential effector molecules to induce changes in their DNA binding properties at their target promoters was assessed. The responses of CbbR(I) and CbbR(II) to potential effectors were not identical. In gel mobility shift assays, the affinity of both CbbR(I) and CbbR(II) for their target promoters was enhanced in the presence of ribulose-1,5-bisphosphate (RuBP), phosphoenolpyruvate, 3-phosphoglycerate, 2-phosphoglycolate. ATP, 2-phosphoglycerate, and KH(2)PO(4) were found to enhance only CbbR(I) binding, while fructose-1,6-bisphosphate enhanced the binding of only CbbR(II). The DNase I footprint of CbbR(I) was reduced in the presence of RuBP, while reductions in the CbbR(II) DNase I footprint were induced by fructose-1,6-bisphosphate, 3-phosphoglycerate, and KH(2)PO(4). The current in vitro results plus recent in vivo studies suggest that CbbR-mediated regulation of cbb transcription is controlled by multiple metabolic signals in R. capsulatus. This control reflects not only intracellular levels of Calvin-Benson-Bassham cycle metabolic intermediates but also the fixed (organic) carbon status and energy charge of the cell.

Bacterial Proteins↗
PubMed1991

Effector domains of human immunodeficiency virus type 1 Rev and human T-cell leukemia virus type I Rex are functionally interchangeable and share an essential peptide motif.

The human immunodeficiency virus type 1 Rev and human T-cell leukemia virus type I Rex transactivators are posttranscriptional regulatory proteins that promote retroviral gene expression by interacting with specific viral mRNAs. Rev and Rex have markedly dissimilar amino acid sequences and RNA target specificities but are thought to act through the same cellular pathway. In this report, we demonstrate that short peptide domains which are required for effector activity in Rev and Rex are functionally interchangeable. Activity of these effector domains depends upon a previously unrecognized tetrapeptide motif that is present in both Rev and Rex and also in analogous proteins from other complex retroviruses. The conserved effector motif may mediate essential interactions of Rev, Rex, and other transactivators of this type with a common cellular cofactor.

Amino Acid Sequence↗
PubMed1994

Posttranscriptional effector domains in the Rev proteins of feline immunodeficiency virus and equine infectious anemia virus.

By systematically dissecting the Rev proteins of feline immunodeficiency virus (FIV) and equine infectious anemia virus (EIAV), we have identified within each a short peptide that is functionally interchangeable with the effector domains found in Rev-like proteins from other retroviruses. The active sequences from FIV and EIAV differ in several respects from other known effectors and may represent a distinct class of effector domain.

Amino Acid Sequence↗
PubMed1997

Virus-specific memory and effector T lymphocytes exhibit different cytokine responses to antigens during experimental murine respiratory syncytial virus infection.

Mice sensitized to the G (attachment) or F (fusion) glycoproteins of respiratory syncytial virus (RSV) expressed different patterns of cytokine production and lung pathology when challenged by intranasal infection with RSV. Five days after challenge, mice sensitized to G glycoprotein produced high levels of interleukin-4 (IL-4) and IL-5 in the lungs and spleens and developed extensive pulmonary eosinophilia, while mice sensitized to F glycoprotein produced IL-2 and developed a mononuclear cell infiltration. Memory lymphocytes isolated 2 weeks after intranasal challenge of mice primed to the G or F glycoprotein secreted only IL-2 and gamma interferon (IFN-gamma) when stimulated with RSV. IL-4 and IL-5 production characteristic of Th2-type effectors in the lung was observed only after multiple rounds of in vitro stimulation of RSV G-specific memory T lymphocytes with antigen. Also IFN-gamma production appeared to play only a minor role in the expression of pulmonary pathology characteristic of Th1 or Th2 T-lymphocyte responses, because mice genetically deficient in IFN-gamma production by gene disruption displayed the same pattern of pulmonary inflammation to RSV infection after priming to RSV F or G as conventional mice. These results suggest that effector T lymphocytes exhibit a different pattern of cytokine production than memory T-lymphocyte precursors precommitted to a Th1 or Th2 pattern of differentiation. Furthermore, these observations raise the possibility that the cytokine response of human memory T lymphocytes after a single exposure to antigen in vitro may not accurately reflect the cytokine response of differentiated effector T lymphocytes at the site of infection in vivo.

Animals↗
PubMed2001

Simian immunodeficiency virus (SIV) infection of a rhesus macaque induces SIV-specific CD8(+) T cells with a defect in effector function that is reversible on extended interleukin-2 incubation.

A vigorous expansion of antigen-specific CD8(+) T cells lacking apparent effector function was observed in a rhesus macaque acutely infected with the simian immunodeficiency virus (SIV) strain SIVmac239. Antigen-specific CD8(+) T cells were identified using antigenic-peptide class I major histocompatibility complex tetramers. As many as 8.3% of CD8(+) cells recognized the Mamu-A*01-associated SIV epitope Gag(181-189) (CTPYDINQM); however, these cells demonstrated no effector function when presented with peptide-incubated targets, as measured by intracellular cytokine staining for gamma interferon (IFN-gamma), interleukin-2 (IL-2) production, or direct cellular lysis. Similar results were observed with three other SIV peptide antigens. Nonresponsiveness did not correlate with apoptosis of the CD8(+) cells, nor were cells from this macaque impaired in their ability to present peptide antigens. Associated with the nonresponsive state was a lack of IL-2 production and decreased IL-2 receptor expression. Exogenous IL-2 treatment for 1 week in the absence of antigenic stimulation restored antigen-specific responses and the quantitative correlation between tetramer recognition and antigen-responsive IFN-gamma secretion. This case report suggests a regulatory mechanism that may impede the effector function of antigen-specific T cells during acute infection with SIV or human immunodeficiency virus in some cases. This mechanism may participate in the failure of the immune system to limit infection.

Animals↗
PubMed2004

Beyond help: direct effector functions of human immunodeficiency virus type 1-specific CD4(+) T cells.

The immune correlates of protection in human immunodeficiency virus type 1 (HIV-1) infection remain poorly defined, particularly the contribution of CD4(+) T cells. Here we explore the effector functions of HIV-1-specific CD4(+) T cells. We demonstrate HIV-1 p24-specific CD4(+)-T-cell cytolytic activity in peripheral blood mononuclear cells directly ex vivo and after enrichment by antigen-specific stimulation. We further show that in a rare long-term nonprogressor, both an HIV-1-specific CD4(+)-T-cell clone and CD4(+) T cells directly ex vivo exert potent suppression of HIV-1 replication. Suppression of viral replication was dependent on cell-cell contact between the effector CD4(+) T cells and the target cells. While the antiviral effector activity of CD8(+) T cells has been well documented, these results strongly suggest that HIV-1-specific CD4(+) T cells are capable of directly contributing to antiviral immunity.

CD4-Positive T-Lymphocytes↗
PubMed2005

Regression of Epstein-Barr virus-induced B-cell transformation in vitro involves virus-specific CD8+ T cells as the principal effectors and a novel CD4+ T-cell reactivity.

T-cell memory to Epstein-Barr virus (EBV) was first demonstrated through regression of EBV-induced B-cell transformation to lymphoblastoid cell lines (LCLs) in virus-infected peripheral blood mononuclear cell (PBMC) cultures. Here, using donors with virus-specific T-cell memory to well-defined CD4 and CD8 epitopes, we reexamine recent reports that the effector cells mediating regression are EBV latent antigen-specific CD4+ and not, as previously assumed, CD8+ T cells. In regressing cultures, we find that the reversal of CD23+ B-cell proliferation was always coincident with an expansion of latent epitope-specific CD8+, but not CD4+, T cells; furthermore CD8+ T-cell clones derived from regressing cultures were epitope specific and reproduced regression when cocultivated with EBV-infected autologous B cells. In cultures of CD4-depleted PBMCs, there was less efficient expansion of these epitope-specific CD8+ T cells and correspondingly weaker regression. The data are consistent with an effector role for epitope-specific CD8+ T cells in regression and an auxiliary role for CD4+ T cells in expanding the CD8 response. However, we also occasionally observed late regression in CD8-depleted PBMC cultures, though again without any detectable expansion of preexisting epitope-specific CD4+ T-cell memory. CD4+ T-cell clones derived from such cultures were LCL specific in gamma interferon release assays but did not recognize any known EBV latent cycle protein or derived peptide. A subset of these clones was also cytolytic and could block LCL outgrowth. These novel effectors, whose antigen specificity remains to be determined, may also play a role in limiting virus-induced B-cell proliferation in vitro and in vivo.

B-Lymphocytes↗
PubMed1991

A ras effector domain mutant which is temperature sensitive for cellular transformation: interactions with GTPase-activating protein and NF-1.

A series of v-rasH effector domain mutants were analyzed for their ability to transform rat 2 cells at either low or high temperatures. Three mutants were found to be significantly temperature sensitive: Ile-36 changed to Leu, Ser-39 changed to Cys (S39C), and Arg-41 changed to Leu. Of these, the codon 39 mutant (S39C) showed the greatest degree of temperature sensitivity. When the same mutation was analyzed in the proto-oncogene form of ras(c-rasH), this gene was also found to be temperature sensitive for transformation. Biochemical analysis of the proteins encoded by v-rasH(S39C) and c-rasH(S39C) demonstrated that the encoded p21ras proteins were stable and bound guanine nucleotides in vivo at permissive and nonpermissive temperatures. On the basis of these findings, it is likely that the temperature-sensitive phenotype results from an inability of the mutant (S39C) p21ras to interact properly with the ras target effector molecule(s) at the nonpermissive temperature. We therefore analyzed the interaction between the c-rasH(S39C) protein and the potential target molecules GTPase-activating protein (GAP) and the GAP-related domain of NF-1, on the basis of stimulation of the mutant p21ras GTPase activity by these molecules in vitro. Assays conducted across a range of temperatures revealed no temperature sensitivity for stimulation of the mutant protein, compared with that of authentic c-rasH protein. We conclude that for this mutant, there is a dissociation between the stimulation of p21ras GTPase activity by GAP and the GAP-related domain NF-1 and their potential target function. Our results are also consistent with the existence of a distinct, as-yet-unidentified effector for mammalian ras proteins.

Animals↗
PubMed1994

Critical binding and regulatory interactions between Ras and Raf occur through a small, stable N-terminal domain of Raf and specific Ras effector residues.

Genetic and biochemical evidence suggests that the Ras protooncogene product regulates the activation of the Raf kinase pathway, leading to the proposal that Raf is a direct mitogenic effector of activated Ras. Here we report the use of a novel competition assay to measure in vitro the relative affinity of the c-Raf-1 regulatory region for Ras-GTP, Ras-GDP, and 10 oncogenic and effector mutant Ras proteins. c-Raf-1 associates with normal Ras and the oncogenic V12 and L61 forms of Ras with equal affinity. The moderately transforming mutant Ras[E30K31] also bound to the c-Raf-1 regulatory region with normal affinity. Transformation-defective Ras effector mutants Ras[N33], Ras[S35], and Ras[N38] bound poorly. In contrast, the transformation defective Ras[G26I27] and Ras[E45] mutants bound to the c-Raf-1 regulatory region with nearly wild-type affinity. A stable, high-affinity Ras-binding region of c-Raf-1 was mapped to a 99-amino-acid subfragment of the first 257 residues. The smallest Ras-binding region identified consisted of N-terminal residues 51 to 131, although stable expression of the domain and high-affinity binding were improved by the presence of residues 132 to 149. Deletion of the Raf zinc finger region did not reduce Ras-binding affinity, while removal of the first 50 amino acids greatly increased affinity. Phosphorylation of Raf[1-149] by protein kinase A on serine 43 resulted in significant inhibiton of Ras binding. demonstrating that the mechanism of cyclic AMP downregulation results through structural changes occurring exclusively in this small Ras-binding domain.

Cyclic AMP-Dependent Protein Kinases↗
PubMed1997

Differential transcription directed by discrete gamma interferon promoter elements in naive and memory (effector) CD4 T cells and CD8 T cells.

Acquisition of the ability to produce gamma interferon (IFN-gamma) is a fundamental property of memory T cells and enables one subset (T helper 1 [TH1]) to deliver its effector functions. To examine regulation of IFN-gamma gene expression in a model system which recapitulates TH1 differentiation, we prepared reporter transgenic mice which express the luciferase gene under the control of proximal and distal regulatory elements (prox.IFN gamma and dist.IFN gamma) from the IFN-gamma promoter. Memory T cells, but not naive T cells, secreted IFN-gamma and expressed both prox.IFN gamma and dist.IFN gamma transcriptional activities. Naive T cells required priming to become producers of IFN-gamma and to direct transcription by these elements. While both CD4+ and CD8+ T cells produced IFN-gamma, only CD4+ T cells expressed prox.IFN gamma transcriptional activity. Induction of transcriptional activity was inhibited by known antagonists of effector T-cell populations. Cyclosporin A inhibited transcriptional activity directed by both elements in effector T cells. Elevated cyclic AMP inhibited transcriptional activity directed by prox.IFN gamma in primed CD4+ T cells but enhanced transcriptional activity directed by dist.IFN gamma in primed CD8+ T cells. Taken together, these data show that prox.IFN gamma and dist.IFN gamma transcriptional activities mirror IFN-gamma gene expression in naive and memory CD4+ T cells but suggest that differences exist in regulation of IFN-gamma gene expression in CD4+ and CD8+ T-cell subsets.

Animals↗
PubMed2002

The RAS effector RIN1 directly competes with RAF and is regulated by 14-3-3 proteins.

Activation of RAS proteins can lead to multiple outcomes by virtue of regulated signal traffic through alternate effector pathways. We demonstrate that the RAS effector protein RIN1 binds to activated RAS with an affinity (K(d), 22 nM) similar to that observed for RAF1. At concentrations close to their equilibrium dissociation constant values, RIN1 and RAF1 compete directly for RAS binding. RIN1 was also observed to inhibit cellular transformation by activated mutant RAS. This distinguishes RIN1 from other RAS effectors, which are transformation enhancing. Blockade of transformation was mediated by the RAS binding domain but required membrane localization. RIN1 recognizes endogenous RAS following transient activation by epidermal growth factor, and a portion of RIN1 fractionates to the cell membrane in a manner consistent with a reversible interaction. RIN1 also binds to 14-3-3 proteins through a sequence including serine 351. Mutation of this residue abolished the 14-3-3 binding capacity of RIN1 and led to more efficient blockade of RAS-mediated transformation. The mutant protein, RIN1(S351A), showed a shift in localization to the plasma membrane. Serine 351 is a substrate for protein kinase D (PKD [also known as PKCmu]) in vitro and in vivo. These data suggest that the normal localization and function of RIN1, as well as its ability to compete with RAF, are regulated in part by 14-3-3 binding, which in turn is controlled by PKD phosphorylation.

14-3-3 Proteins↗
PubMed2002

Exertion of the suppressive effects of IFN-gamma on experimental immune mediated blepharoconjunctivitis in Brown Norway rats during the induction phase but not the effector phase.

BACKGROUND/AIMS: Interferon gamma (IFN-gamma) knockout mice exhibit severe allergic conjunctivitis (AC), indicating that IFN-gamma regulates the development of AC. The authors examined whether this inhibitory effect of IFN-gamma is exerted during the induction or effector phase of experimental AC. METHODS: Experimental immune mediated blepharoconjunctivitis (EC) was induced in Brown Norway (BN) rats, using ovalbumin (OVA) as the antigen. To investigate the role of IFN-gamma in the induction phase, EC was induced by active immunisation and IFN-gamma (10 micro g/time, total 70 micro g), or phosphate buffered saline (PBS) as a control, was injected intraperitoneally every other day from the day of immunisation. The rats were challenged with OVA eye drops 13 days after immunisation, and 24 hours later, the eyes were harvested for histology. To examine the effects of IFN-gamma in the effector phase, OVA specific T cells were transferred into syngeneic rats and IFN-gamma (10 micro g/time, total 50 micro g) or PBS was injected each day after the transfer until induction of EC 4 days later with an OVA challenge. To investigate the role of endogenous IFN-gamma during the effector phase, an anti-IFN-gamma monoclonal antibody (3 mg/time) was injected on days 3 and 4. RESULTS: Injection of IFN-gamma into actively immunised rats suppressed eosinophilic infiltration but not infiltration of mononuclear cells. In contrast, neither IFN-gamma nor anti-IFN-gamma affected EC in passively immunised rats. CONCLUSION: IFN-gamma is a suppressive cytokine for the development of EC and exerts this suppressive effect during the induction phase.

Adoptive Transfer↗
PubMed2002

S antigen specific effector T cell activation detected by cytokine flow cytometry.

BACKGROUND/AIMS: Effector T cell activation is particularly important in the initiation of autoimmune uveitis. This pilot study seeks to demonstrate activation of human peripheral effector T cells in response to the uveitis candidate autoantigen, retinal S antigen (SAg), using cytokine flow cytometry (CFC). METHODS: Peripheral blood mononuclear cell (PBMC) suspensions from uveitis patients and controls were stimulated with bovine SAg. Activation responses were detected by CFC. RESULTS: Electronic gating enabled analysis of CD69+, IFN-gamma+ CD4+ lymphocytes. An SAg specific response was detectable in four of 13 patients and four of eight controls. CONCLUSION: SAg specific, peripheral, effector T cell activation can be detected by CFC. Similar levels of responsiveness were seen in patient and control groups. More detailed cytokine profiling may demonstrate functional differences between the groups.

Arrestin↗
PubMed1998

Suppressive activity of the chloroform extract of Tripterygium wilfordii Hook f on effector T cell activation during Hymenolepis nana infection in mice.

The chloroform extract of Tripterygium wilfordii Hook f (TWH extract) administered into mice daily at doses of 80.0 to 200.0 micrograms/kg (but not 40.0 micrograms/kg) caused suppression of protective immunity to Hymenolepis nana when the extract was injected subcutaneously during the induction phase of protective immunity. Daily administration of 200.0 micrograms/kg TWH extract, during the course of larval development from challenge, also suppressed protective immunity. Inhibition of protective immunity was only observed in mice that received TWH extract for 6 days at a daily dose of 200.0 micrograms/kg and were challenged 24 h after the final injection. TWH extract did not inhibit formation of effector cells that mediate delayed type hypersensitivity (DTH) to H. nana egg antigen when the extract was administered subcutaneously at a dose of 200.0 micrograms/kg/day for 5 days before cell preparation. However, TWH extract did inhibit DTH effector cell activation when cells prepared from infected, PBS-injected mice were transferred into 200.0 micrograms/kg TWH extract-treated recipient mice. These results strongly indicate that TWH extract cannot inhibit the generation of effector cells but will suppress their function in vivo.

Animals↗