RESUMO
When facial nerve axotomy (FNA) is performed on immunodeficient recombinase activating gene-2 knockout (RAG-2-/-) mice, there is greater facial motoneuron (FMN) death relative to wild type (WT) mice. Reconstituting RAG-2-/- mice with whole splenocytes rescues FMN survival after FNA, and CD4+ T cells specifically drive immune-mediated neuroprotection. Evidence suggests that immunodysregulation may contribute to motoneuron death in amyotrophic lateral sclerosis (ALS). Immunoreconstitution of RAG-2-/- mice with lymphocytes from the mutant superoxide dismutase (mSOD1) mouse model of ALS revealed that the mSOD1 whole splenocyte environment suppresses mSOD1 CD4+ T cell-mediated neuroprotection after FNA. The objective of the current study was to characterize the effect of CD4+ T cells on the central molecular response to FNA and then identify if mSOD1 whole splenocytes blocked these regulatory pathways. Gene expression profiles of the axotomized facial motor nucleus were assessed from RAG-2-/- mice immunoreconstituted with either CD4+ T cells or whole splenocytes from WT or mSOD1 donors. The findings indicate that immunodeficient mice have suppressed glial activation after axotomy, and cell transfer of WT CD4+ T cells rescues microenvironment responses. Additionally, mSOD1 whole splenocyte recipients exhibit an increased astrocyte activation response to FNA. In RAG-2-/-â¯+â¯mSOD1 whole splenocyte mice, an elevation of motoneuron-specific Fas cell death pathways is also observed. Altogether, these findings suggest that mSOD1 whole splenocytes do not suppress mSOD1 CD4+ T cell regulation of the microenvironment, and instead, mSOD1 whole splenocytes may promote motoneuron death by either promoting a neurotoxic astrocyte phenotype or inducing Fas-mediated cell death pathways. This study demonstrates that peripheral immune status significantly affects central responses to nerve injury. Future studies will elucidate the mechanisms by which mSOD1 whole splenocytes promote cell death and if inhibiting this mechanism can preserve motoneuron survival in injury and disease.
Assuntos
Linfócitos T CD4-Positivos/fisiologia , Nervo Facial/imunologia , Nervo Facial/fisiologia , Esclerose Lateral Amiotrófica/imunologia , Animais , Axotomia/métodos , Linfócitos T CD4-Positivos/imunologia , Morte Celular/fisiologia , Sobrevivência Celular/fisiologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Modelos Animais de Doenças , Traumatismos do Nervo Facial , Núcleo do Nervo Facial , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios Motores/imunologia , Neuroproteção , Baço/imunologia , Superóxido Dismutase/genéticaRESUMO
While it is well known that CD4(+) T cells and B cells collaborate for antibody production, our group previously reported that CD8(+) T cells down-regulate alloantibody responses following transplantation. However, the exact mechanism involved in CD8(+) T cell-mediated down-regulation of alloantibody remains unclear. We also reported that alloantibody production is enhanced when either perforin or FasL is deficient in transplant recipients. Here, we report that CD8(+) T cell-deficient transplant recipient mice (high alloantibody producers) exhibit an increased number of primed B cells compared to WT transplant recipients. Furthermore, CD8(+) T cells require FasL, perforin and allospecificity to down-regulate posttransplant alloantibody production. In vivo CD8-mediated clearance of alloprimed B cells was also FasL- and perforin-dependent. In vitro data demonstrated that recipient CD8(+) T cells directly induce apoptosis of alloprimed IgG1(+) B cells in co-culture in an allospecific and MHC class I-dependent fashion. Altogether these data are consistent with the interpretation that CD8(+) T cells down-regulate posttransplant alloantibody production by FasL- and perforin-dependent direct elimination of alloprimed IgG1(+) B cells.
Assuntos
Linfócitos B/imunologia , Linfócitos T CD8-Positivos/imunologia , Proteína Ligante Fas/metabolismo , Hepatócitos/imunologia , Isoanticorpos/imunologia , Perforina/metabolismo , Animais , Formação de Anticorpos , Western Blotting , Células Cultivadas , Citometria de Fluxo , Imunoglobulina G/imunologia , Imunoglobulina G/metabolismo , Isoanticorpos/metabolismo , Transplante de Fígado , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Transplante Homólogo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
IL-2 and IL-4 induce a synergistic proliferative response in HT-2 cells, suggesting that IL-2Rs and IL-4Rs may interact. The purpose of this study was to examine the effect of IL-4 on the expression and function of IL-2Rs. Preincubation of HT-2 and BCL1-3B3 cells with IL-4 for 60 min at 4 degrees C or 37 degrees C resulted in a partial decrease in the number, but not the affinity of high affinity IL-2Rs as evidenced by Scatchard analysis of binding data. The decrease in the number of high affinity receptors correlated with decreased internalization of IL-2. After preincubation with IL-4, crosslinking of 125I-IL-2 to high affinity IL-2Rs also demonstrated a approximately 50% reduction in the number of high affinity IL-2Rs. Another lymphokine, IL-1, which acts on HT-2 cells, had no measurable effect on the affinity or number of IL-2Rs. Taken together, these results indicate that IL-4 downregulates the expression of high affinity IL-2Rs on some cells. It is not known whether this occurs by a direct ligand-mediated receptor interaction, by the sharing of a common receptor subunit, or by interaction of the two receptors with another membrane molecule or cytoskeletal component.
Assuntos
Linfócitos B/fisiologia , Receptores de Interleucina-2/fisiologia , Receptores Mitogênicos/fisiologia , Linfócitos T Auxiliares-Indutores/fisiologia , Sinergismo Farmacológico , Endocitose , Humanos , Interleucina-2/metabolismo , Interleucina-2/farmacologia , Interleucina-4 , Interleucinas/metabolismo , Interleucinas/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Substâncias Macromoleculares , Peso Molecular , Receptores de Interleucina-4 , Células Tumorais CultivadasRESUMO
Murine Th1 and Th2 subsets differ not only in the lymphokines they produce, but also functionally. It is not clear what factors influence the preferential activation of one subset versus the other and what regulatory interactions exist between them. The purpose of this study was to examine the effect of lymphokines produced by clones of Th1 cells (IL-2 and IFN-gamma), Th2 cells (IL-4), and APC (IL-1) on the proliferative response of Th1 and Th2 cells after antigenic stimulation. Activation of both types of clones in the presence of antigen and APC resulted in the acquisition of responsiveness to the proliferative effects of both IL-2 and IL-4, although Th2 cells were more responsive to IL-4 than Th1 cells. Responsiveness of Th1 and Th2 cells to both lymphokines decreased with time after initial antigenic activation; Th1 cells lost their responsiveness to IL-4 more rapidly and to IL-2 more slowly than Th2 cells. IFN-gamma partially inhibited the IL-2 and IL-4-mediated proliferation of Th2, but not Th1 cells. Although the presence of IL-1 was not required for the response of Th1 or Th2 cells to IL-4, its presence resulted in a synergistic effect with IL-2 or IL-4 in Th2 but not in Th1 cells. Both subsets responded to a mixture of IL-2 and IL-4 in synergistic fashion. Delayed addition and wash-out experiments indicated that both IL-2 and IL-4 had to be present simultaneously in order for synergy to occur. These results suggest that Th cell subsets might regulate each other via the lymphokines that they secrete and that the pathways of IL-2 and IL-4 mediated proliferation are interrelated.
Assuntos
Interleucina-2/farmacologia , Interleucinas/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Linfocinas/farmacologia , Proteínas Recombinantes/farmacologia , Linfócitos T Auxiliares-Indutores/classificação , Animais , Anticorpos Anti-Idiotípicos/imunologia , Linhagem Celular , Células Cultivadas , Células Clonais , Feminino , Interferon Tipo I/farmacologia , Interferon gama/farmacologia , Interleucina-1/imunologia , Interleucina-4 , Camundongos , Camundongos Endogâmicos BALB C , Linfócitos T Auxiliares-Indutores/imunologiaRESUMO
BACKGROUND: Conventional chest radiographs do not afford consistently good visualisation of the main bronchi and sub-carinal angle. Improved visualisation would facilitate accurate measurement of the airways, definition of normal radiographic anatomy and, possibly, earlier identification of extrinsic compression or displacement. AIM: The main objective of this study was to establish whether the paediatric main bronchi and sub-carinal angle could be measured consistently on AP supine chest images obtained using a specific digital radiographic system (DRS). SUBJECTS AND METHODS: The proximal bronchial diameters were measured on supine DRS chest images of 102 children between the ages of 6 months and 13 years. RESULTS: The left and right main bronchi could be seen clearly and measured in over 90% of cases, with intraclass correlation co-efficients of reliability indicating high intra- and inter-observer agreement. The sub-carinal angle had lower intra- and inter-observer agreement. CONCLUSION: Supine chest images acquired using DRS facilitate accurate measurement of the main bronchi and sub-carinal angle in children. Further work is required to establish population-specific age-related norms for bronchial dimensions. These could serve as reference standards for early detection of deviations from normal.
Assuntos
Broncografia , Intensificação de Imagem Radiográfica/métodos , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Projetos Piloto , Estudos Retrospectivos , Tomografia Computadorizada por Raios XRESUMO
The immune system functions to protect an organism against microbial infections and may be involved in the reparative response to nerve injury. The goal of this study was to determine whether the immune system plays a role in regulating motoneuron survival after a peripheral nerve injury. After a right facial nerve axotomy, facial motoneuron (FMN) survival in C.B-17 (+/+) wild-type mice was found to be 87 +/- 3.0% of the unaxotomized left side control. In contrast, facial nerve axotomy in C.B-17 (-/-) severe combined immunodeficient (scid) mice, lacking functional T and B lymphocytes, resulted in an average FMN survival of 55 +/- 3.5% relative to the unaxotomized left side control. This represented an approximately 40% decrease in FMN survival compared with wild-type controls. The reconstitution of scid mice with wild-type splenocytes containing T and B lymphocytes restored FMN survival in these mice to the level of the wild-type controls. These results suggest that immune cells associated with acquired immunity play a role in regulating motoneuron survival after a peripheral nerve injury.
Assuntos
Nervo Facial/patologia , Neurônios Motores/fisiologia , Neuroimunomodulação/fisiologia , Animais , Axotomia , Linfócitos B/fisiologia , Linfócitos B/transplante , Sobrevivência Celular/imunologia , Nervo Facial/imunologia , Traumatismos do Nervo Facial/patologia , Feminino , Camundongos , Camundongos SCID , Neurônios Motores/imunologia , Neurônios Motores/patologia , Baço/citologia , Linfócitos T/fisiologia , Linfócitos T/transplanteRESUMO
One major obstacle in studying the activation of antigen-specific B cells is the small number of B cells reactive with a particular antigenic epitope. In this report, we describe a method by which large numbers of highly purified antigen-binding cells can be obtained. We have shown that by varying the haptenation level of the erythrocytes used for rosetting, we can purify antigen-binding B cells which have different affinities for the antigenic epitope. Thus, memory cells (which have receptors of higher affinity) can be prepared and these cells are essentially free of contaminating virgin cells. The effects of varying the haptenation levels on the red cells used for purifying the B cells can, in turn, be related to the precursor frequency of secreting cells following their activation with T cells and antigen.
Assuntos
Linfócitos B/imunologia , Separação Celular/métodos , Animais , Afinidade de Anticorpos , Aspirina/farmacologia , Relação Dose-Resposta Imunológica , Eritrócitos , Feminino , Memória Imunológica , Camundongos , Camundongos Endogâmicos BALB C , Receptores de Antígenos de Linfócitos B/imunologia , Formação de Roseta , Trinitrobenzenos/imunologiaRESUMO
Resting mouse splenic B cells were activated with lipopolysaccharide/dextran sulfate (LPS/DxS) to measure both B cell proliferation and IgM/IgG isotype production when increasing concentrations of [Met5]-enkephalin (MENK) and proenkephalin (PENK) (10-16 to 10(-8) M) were added at increasing times after B cell activation (0, 3, 6, or 24 h). Results show that proliferation was not affected by either peptide, but that IgM, IgG3 and IgG2a production were inhibited in a concentration- and time-dependent manner by MENK. IgG1 production was unaffected by MENK. In contrast, PENK induced no change in the production of Ig isotypes at any time point of addition, with the exception of IgG1 and IgG2a that were enhanced when PENK was added 6 h after cell activation. In the absence of LPS/DxS activation, no change in the level of any Ig isotype was induced by either peptide.
Assuntos
Linfócitos B/metabolismo , Encefalina Metionina/administração & dosagem , Encefalinas/administração & dosagem , Imunoglobulina G/biossíntese , Imunoglobulina M/biossíntese , Precursores de Proteínas/administração & dosagem , Animais , Linfócitos B/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Sulfato de Dextrana/farmacologia , Relação Dose-Resposta a Droga , Encefalina Metionina/farmacologia , Encefalinas/farmacologia , Feminino , Lipopolissacarídeos/farmacologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos BALB C , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Concentração Osmolar , Precursores de Proteínas/farmacologiaRESUMO
A system for metabolic activation of cyclophosphamide (CP), consisting of a crude microsomal fraction of mouse liver and necessary cofactors (S9 mix), was interfaced with three murine cell culture assays for immunotoxicity. These assays were: the Mishell-Dutton assay for in vitro antibody formation, splenic lymphocyte responsiveness to mitogens and bone marrow cell cultures. There was no effect of CP at doses up to 261 microgram/ml (lmM) on any of the parameters measured unless S9 mix was included. Much greater potency was achieved if the S9 mix was prepared from livers of mice pretreated with phenobarbital. Under these conditions and dose-related inhibition of plaque-forming cells (PFC) in the Mishell-Dutton assay was observed, yielding an ED50 of 6.3 microgram/ml. When splenic lymphocytes were exposed to CP in the presence of induced S9 mix, a dose related inhibition of the response to the B-cell mitogen, lipopolysaccharide (LPS), and to the T-cell mitogen, concanavalin A (Con A), was observed. For the optimum LPS concentration, the ED50 for CP was 8.1 microgram/ml; for the optimum concentration of Con A, the ED50 was 6.7 microgram/ml. DNA synthesis was not inhibited by the doses used. When bone marrow cells were exposed to CP in the presence of induced S9 mix, the stem cell population, enumerated by colonization in semisolid medium, was reduced in a dose-dependent manner, with an ED50 of 5.2 microgram/ml. Again, DNA synthesis was not affected unless higher doses of CP were used.
Assuntos
Técnicas Imunológicas , Imunossupressores/toxicidade , Animais , Formação de Anticorpos/efeitos dos fármacos , Biotransformação , Medula Óssea/efeitos dos fármacos , Ciclofosfamida/metabolismo , DNA/biossíntese , Imunossupressores/metabolismo , Técnicas In Vitro , Linfócitos/efeitos dos fármacos , Masculino , Camundongos , Microssomos Hepáticos/metabolismo , Mitógenos/farmacologiaRESUMO
Chloral hydrate has been found in our drinking water supplies at levels up to 5 micrograms/1. The purpose of this study was to evaluate the functional status of the immune system in random-bred CD-1 mice exposed to chloral hydrate for 14 and 90 days. Male mice, following 14 or 90 days of exposure to 1/10 and 1/100 the actual oral LD50, exhibited no alterations in either humoral or cell-mediated immunity. However, female mice exposed for 90 days to chloral hydrate in the drinking water demonstrated a significant depression in humoral immune function. This depression was observed when spleen cells from exposed mice were evaluated for their ability to produce antibody against sheep erythrocytes. These females did not demonstrate any changes in cell-mediated immune status.
Assuntos
Formação de Anticorpos/efeitos dos fármacos , Hidrato de Cloral/toxicidade , Imunidade Celular/efeitos dos fármacos , Animais , Linfócitos B/efeitos dos fármacos , DNA/biossíntese , Eritrócitos/imunologia , Camundongos , Mitógenos/farmacologia , Sistema Fagocitário Mononuclear/efeitos dos fármacos , Ovinos/imunologia , Linfócitos T/efeitos dos fármacosRESUMO
This study evaluated the subchronic toxicity of selected halomethanes which are drinking water contaminants. The compounds studied were trichloromethane, bromodichloromethane, dibromochloromethane and tribromomethane. Subchronic 14-day gavage studies were performed with the use of doses encompassing one-tenth the LD50 for the compounds. A 90-day gavage study of one of the compounds, trichloromethane, was also done. Parameters observed included body and organ weights, histopathology, hematology, clinical chemistries, and hepatic microsomal enzyme activities. Toxicity to the humoral immune system was assessed by measuring the number of splenic IgM antibody-forming cells and the serum antibody level to sheep erythrocytes. Cell-mediated immunity was evaluated by measuring the delayed type hypersensitivity response and popliteal lymph node proliferation response to sheep red blood cells. The functional activity of the reticuloendothelial system, as measured by the vascular clearance rate and tissue uptake of 51Cr sheep red blood cells was also determined. The major effects of the halomethanes were increased liver weights, elevations of SGPT and SGOT, decreased spleen weights and a decrease in the number of splenic IgM antibody-forming cells. The humoral immune system appeared to be an indicator of halomethane toxicity. There is evidence that subchronic 14-day exposure may be of greater value than long-term studies in determining the toxicity of these compounds.
Assuntos
Hidrocarbonetos Halogenados/toxicidade , Poluentes Químicos da Água/toxicidade , Poluentes da Água/toxicidade , Administração Oral , Animais , Sangue/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Masculino , Camundongos , Tamanho do Órgão/efeitos dos fármacosRESUMO
The organs, tissues, and cells of the lymphoreticular system have received considerable attention as targets for chemicals causing adverse effects. A basic toxicological approach is described for assessing the risk of a chemical perturbing the immune system. CD-1 mice were exposed for 14 or 90 days to one of several chlorinated hydrocarbons: 1,2-dichloroethane, 1,2-dichloroethylene or 1,1,2-trichloroethylene. Other mice were exposed to dexamethasone, a known immunosuppressive agent. The immune system is evaluated against a background of the more standard toxicological parameters such as fluid consumption, body and organ weights, hematology, clinical chemistries, and blood coagulation. Reported here are the results for the male mice after 14-day exposure to three chlorinated hydrocarbons and after 90-day exposure to 1,2-dichloroethane and dexamethasone.Acute toxicity studies were performed to provide a basis for doses used in the subchronic studies. The LD(50) values are reported. The status of the humoral immune system was determined by measuring the number of IgM spleen antibody-forming cells to sRBC, the serum antibody level to sRBC, and the lymphocyte response to the B-cell mitogen, LPS. Of the three chlorinated hydrocarbons, only dichloroethane produced a significant (p < 0.05) reduction in antibody-forming cells. The other two chemicals produced trends towards suppression. Mice exposed to dichloroethane in the drinking water for 90 days showed no alteration in AFC, serum antibody titers or response to the B-lymphocyte mitogen, LPS. Subchronic 90-day exposure to dexamethasone produced a dose-dependent inhibition of AFC/spleen but not AFC/10(6) spleen cells when measured on the peak day of response. Response to LPS was not altered, and spleen weight and spleen cell number were reduced as much as 42%. These data suggest that dexamethasone administered in the drinking water is nonspecifically cytotoxic to the spleen cells.Cell-mediated immunity was assessed by measuring the DTH response to sRBC and the response to the T-lymphocyte mitogen, concanavalin A. After 14 days of exposure, trichloroethylene produced a 15 and 60% suppression at 24 and 240 mg/kg, respectively. Dichloroethylene produced a non-dose-dependent inhibition at 4.9 and 49 mg/kg, which was slight, but significant (p < 0.05). Subchronic 90-day exposure to dichloroethane did not alter the DTH response or spleen lymphocyte response to concanavalin A. In contrast, dexamethasone produced a dose-dependent inhibition of the DTH response and a hyperresponsiveness to concanavalin A.Dichloroethane did not alter the functional activity of the reticuloendothelial system, as measured by the vascular clearance rate and tissue uptake of (51)Cr sRBC. In the case of dexamethasone exposure, only the spleen and thymus showed decreased uptake of (51)Cr sRBC, which was directly related to decrease in size. The approaches and results from these types of studies provide a basis for judging a chemical's potential risk to the immune system.
Assuntos
Dexametasona/toxicidade , Dicloroetilenos/toxicidade , Dicloretos de Etileno/toxicidade , Hidrocarbonetos Clorados/toxicidade , Imunidade/efeitos dos fármacos , Tricloroetileno/toxicidade , Animais , Formação de Anticorpos/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Hipersensibilidade Tardia , Imunidade Celular/efeitos dos fármacos , Dose Letal Mediana , Masculino , Camundongos , Camundongos Endogâmicos , Sistema Fagocitário Mononuclear/efeitos dos fármacos , Tamanho do Órgão/efeitos dos fármacosRESUMO
Chloral hydrate has been found in our drinking water supplies at levels up to 5 micrograms/1. The purpose of this study was to evalute the acute and subchronic toxicology of chloral hydrate in the random-bred CD-1 mouse, to provide data for risk assessment. The acute oral LD50 of this compound was 1442 and 1265 mg/kg in male and female mice, respectively. Acute toxicity appeared to be related to depression of the central nervous system. Fourteen-day exposure by gavage in male mice at doses 1/10 and 1/100 the LD50 caused an increase in liver weight and a decrease in spleen weight at the highest dose level. Based on the data derived from 14 days of exposure, a 90-day study was performed. The compound was delivered via the drinking water; levels of the compound delivered per day were equivalent to those dosed in the 14-day study. The target organ in both sexes appeared to be the liver, with the males most affected. Male mice demonstrated a dose-related hepatomegaly accompanied by significant changes in serum chemistries and hepatic microsomal parameters. The females did not demonstrate the hepatomegaly observed in males, but did show alterations in hepatic microsomal parameters. No other significant toxicological changes were observed in either sex following 90 days of exposure.
Assuntos
Hidrato de Cloral/toxicidade , Administração Oral , Animais , Coagulação Sanguínea , Peso Corporal/efeitos dos fármacos , Enzimas/sangue , Feminino , Dose Letal Mediana , Masculino , Camundongos , Microssomos Hepáticos/metabolismo , Tamanho do Órgão/efeitos dos fármacos , Fatores de TempoAssuntos
Linfócitos B/imunologia , Norepinefrina/fisiologia , Receptores Adrenérgicos beta 2/fisiologia , Células Th1/imunologia , Células Th2/imunologia , Linfócitos B/efeitos dos fármacos , Humanos , Ativação Linfocitária , Sistema Nervoso Simpático/imunologia , Células Th1/efeitos dos fármacos , Células Th2/efeitos dos fármacosRESUMO
Adrenoceptors are heterotrimeric glycoproteins that bind specific endogenous ligands, such as the sympathetic neurotransmitter norepinephrine and the neurohormone epinephrine. Ligand binding to an adrenoceptor expressed on the cell surface initiates a cascade of biochemical and molecular responses inside the cell that lead to a change in cellular activity. Initially, the stimulation of an adrenoceptor directly activates G proteins that stimulate enzymes to induce the production of second messengers. The cascade continues as the second messengers activate serine/threonine protein kinases, resulting in either an inhibition or enhancement of cellular activity. The resulting changes in cellular activity are mediated by changes in gene expression that are induced by the phosphorylation of specific transcription factors. Adrenoceptor subtypes are expressed by both T and B lymphocytes. The aim of this review is to summarize and discuss the results from the many studies that have examined the role of adrenoceptor-mediated intracellular signals in the modulation of lymphocyte function. Another aim of this review is to discuss how these studies have advanced our understanding of the mechanisms by which the sympathetic nervous system transmits information to both T and B lymphocytes to maintain immune homeostasis.
Assuntos
Linfócitos/imunologia , Receptores Adrenérgicos/fisiologia , Transdução de Sinais/fisiologia , Adrenérgicos/farmacologia , Animais , Formação de Anticorpos , Apresentação de Antígeno , AMP Cíclico/fisiologia , Humanos , Ativação Linfocitária , Cooperação Linfocítica , Subpopulações de Linfócitos/efeitos dos fármacos , Subpopulações de Linfócitos/imunologia , Subpopulações de Linfócitos/metabolismo , Linfócitos/efeitos dos fármacos , Linfócitos/metabolismo , Modelos Biológicos , Fosforilação , Processamento de Proteína Pós-Traducional , Receptores Adrenérgicos/classificação , Receptores Adrenérgicos/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacosRESUMO
The mechanism by which the Th2 cell-dependent Ab response is modulated by the sympathetic neurotransmitter norepinephrine (NE) was investigated. Our model system used the severe combined immunodeficient (scid) mouse that was depleted of NE with 6-hydroxydopamine before reconstitution with a clone of beta2-adrenergic receptor (beta2AR)neg KLH-specific Th2 cells and resting trinitrophenyl (TNP)-specific beta2ARpos B cells enriched from the spleens of unimmunized mice. Following challenge with TNP-keyhole limpet hemocyanin (KLH), Ab production in these mice was hapten-, carrier-, and allotype-specific as well as MHC restricted. Depletion of NE resulted in a 50-75% suppression of the primary anti-TNP IgM response compared with that of NE-intact controls, while the secondary IgM response returned to control levels. In contrast, both the primary and secondary anti-TNP IgG1 responses were suppressed by 85 and 40%, respectively. Using NE-intact mice exposed to either a betaAR- or alphaAR-selective antagonist, the effect of NE on the Ab response was shown to be mediated by the betaAR. In addition, administration of a beta2AR-selective agonist to NE-depleted mice partially reversed the suppressed Ab response that resulted from NE depletion. Expression of the beta2AR on TNP-specific B cells was confirmed by radioligand binding, immunofluorescence, and cAMP analysis. Also, while splenic histology was comparable in NE-intact and NE-depleted mice before Ag exposure, follicle expansion and germinal center formation were suppressed in NE-depleted mice after Ag exposure. Taken together, these results suggest that NE stimulation of the beta2AR expressed on B cells is necessary for the maintenance of an optimal primary and secondary Th2 cell-dependent Ab response in vivo.
Assuntos
Epitopos de Linfócito T/imunologia , Tolerância Imunológica , Imunoglobulina G/biossíntese , Imunoglobulina M/biossíntese , Norepinefrina/metabolismo , Células Th2/imunologia , Animais , Especificidade de Anticorpos , Linfócitos B/transplante , Células Clonais/transplante , Epitopos de Linfócito B/imunologia , Feminino , Haptenos/imunologia , Hemocianinas/imunologia , Tolerância Imunológica/genética , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos SCID , Norepinefrina/genética , Receptores Adrenérgicos beta/fisiologia , Simpatectomia Química , Células Th2/transplante , Trinitrobenzenos/imunologiaRESUMO
The beta adrenoceptor has been identified in this study to be the receptor responsible for the enhanced immunoglobulin M antibody response produced by norepinephrine in mouse spleen cells immunized with sheep erythrocytes in vitro. The magnitude and kinetics of the enhanced antibody response to norepinephrine alone, or to norepinephrine in the presence of phentolamine, were more closely mimicked with a beta-2 adrenoceptor agonist (terbutaline) than with a beta-1 adrenoceptor agonist (dobutamine). Norepinephrine alone, norepinephrine in the presence of phentolamine, or terbutaline exposure produced a number of spleen cells secreting immunoglobulin M antibody that is equal to control on day 4 after immunization and which is enhanced above control on days 5, 6 and 7. Dobutamine causes no change when compared to control on days 4 and 5, but causes a delayed decline in the response on days 6 and 7. All drug responses were concentration-dependent and propranolol antagonized the enhanced response observed in the presence of terbutaline or dobutamine alone. When norepinephrine was added to immunized spleen cell cultures in the presence of propranolol, an alpha adrenoceptor-mediated component was unmasked which produced an enhanced response on day 4 after immunization and returned to control levels on days 5, 6 and 7. These results suggest that antibody responses can be modulated positively by a sympathetic neurotransmitter. This up-modulation by norepinephrine is beta adrenoceptor-mediated at the time of, and after, peak control response and alpha adrenoceptor-mediated 1 day before peak control response.
Assuntos
Formação de Anticorpos/efeitos dos fármacos , Norepinefrina/farmacologia , Receptores Adrenérgicos beta/metabolismo , Animais , Dobutamina/farmacologia , Feminino , Técnicas In Vitro , Isoproterenol/farmacologia , Cinética , Camundongos , Camundongos Endogâmicos C57BL , Fentolamina/farmacologia , Propranolol/farmacologia , Terbutalina/farmacologiaRESUMO
TNP-specific B cells interact with carrier-specific T hybridoma cells in an antigen-specific, MHC-restricted manner. The formation of T cell/B cell conjugates is time and temperature dependent and results in the formation of a broad area of close contact between the interacting cells. In order to determine which surface molecules on the two cells cluster at the interaction site. T cell/B cell conjugates were formalin-fixed at different times following conjugation and were stained with antibodies directed against cell surface molecules. Results of these studies indicate that the alpha- and beta-subunits of LFA-1 on B cells transiently cluster in the area of cell contact. Maximum clustering of LFA-1 occurs at 45 min, after which time LFA-1 redistributes on the surface of the B cells. Several other B cell-associated molecules (MHC Class II, ICAM-1, Ig, B220, J11D, or CD23) do not cluster at the interaction site at any time point. T cell-associated LFA-1 does not cluster with any specific pattern, but ICAM-1 does. Maximum clustering of ICAM-1 occurs 60 to 90 min after intercellular contact. After this time, ICAM-1 redistributes on the surface of the T cells. Although both the alpha- and beta-subunits of LFA-1 cluster at the interaction site on B cells, antibodies recognizing these subunits differ in their ability to affect conjugation. One antibody recognizing the alpha chain of LFA-1 (M17/4.2) inhibits T-cell/B cell conjugation, whereas another antibody that also recognizes the alpha chain-(G-48) enhances conjugation. In contrast, an antibody that recognizes LFA-1 beta (M18/2.a.8) has no effect. An antibody that recognizes ICAM-1 (YN/1.7), the ligand for LFA-1, inhibits conjugation. These data show that, during T cell/B cell interaction. LFA-1 on B cells and ICAM-1 on T cells transiently cluster with similar, albeit not identical, kinetics to the site of cell-cell contact.