RESUMEN

BACKGROUND: Tobacco use among women during pregnancy leading to poor maternal and child health outcomes has been well documented. However, factors influencing use of smokeless tobacco in Nepal has not yet been well established. This study aims at exploring the factors related to smokeless tobacco use among pregnant women in rural southern Terai of Nepal. METHODS: A community-based cross-sectional study was performed at 52 wards within 6 Village Development Committee in Dhanusha district of Nepal. A total of 426 expectant mothers in their second trimester were selected using a multistage cluster sampling method. Descriptive and regression analyses were done to explore the factors that influence smokeless tobacco use. RESULTS: In a total of 426 pregnant mothers, one in five used tobacco in any form. Among the users, 13.4% used smokeless tobacco. Pregnant mothers who were smoking tobacco (AOR 6.01; 95% CI (1.88-19.23), having alcohol consumption (AOR 3.86; 95% CI (1.23-12.08), stressed (AOR 5.04; 95% CI (1.81-14.03), non-vegetarian (AOR 3.31;(1.84-13.03), not attending regular mothers' group meetings (AOR 4.63; (1.41-15.19), and not-exposed to mass media (AOR 5.02; (1.89-13.33) were significantly associated with smokeless tobacco use. Similarly, mothers of age group 20-34 years, dalit, aadibasi and janajati, hill origin, no education and primary education were more likely to use smokeless tobacco than their counterparts. CONCLUSIONS: Factors such as smoking tobacco, alcohol consumption, stress, and poor education were found to be significantly associated with smokeless tobacco use among pregnant women in southern Terai of Nepal. This requires an immediate attention develop an effective strategy to prevent and control smokeless tobacco use among pregnant women in southern Terai of Nepal.

Asunto(s)

Población Rural/estadística & datos numéricos , Tabaco sin Humo/estadística & datos numéricos , Adulto , Factores de Edad , Consumo de Bebidas Alcohólicas/epidemiología , Estudios Transversales , Dieta , Femenino , Encuestas Epidemiológicas , Humanos , Persona de Mediana Edad , Nepal/epidemiología , Embarazo , Segundo Trimestre del Embarazo , Análisis de Regresión , Fumar/epidemiología , Factores Socioeconómicos , Estrés Psicológico/epidemiología , Productos de Tabaco/estadística & datos numéricos , Adulto Joven

RESUMEN

BACKGROUND: Dermal elastosis is considered the histological 'gold standard' for evaluation of skin photoaging, but the relation of the level of dermal elastosis to other histological indicators of photoaging is not clear. OBJECTIVE: To investigate how various proposed histological measures of photoaging compare with the level of dermal elastosis. METHODS: Prospective, community-based study in Southeast Queensland, Australia, among 89 participants aged 40-82 years. Quantitative histology was used to evaluate 8 biomarkers of photoaged skin, and associations between grades of dermal elastosis and each of the other 7 biomarkers were analysed using ordinal logistic regression models with proportional odds assumption, using histological grades of elastosis as the outcome. RESULTS: Older age, male sex and high outdoor exposure levels were confirmed as predictors of high levels of dermal elastosis. After adjustment for age and sex, the only significant positive association with increasing elastosis grades was the proportion of p53-positive cells. Epidermal thickness, interdigitation index proportion of surface covered with melanin (% Fontana-Masson staining) and glycosaminoglycan content were not associated with elastosis in either crude or adjusted models. CONCLUSIONS: Among a range of suggested biomarkers of photoaged skin, only p53-positive cells appear to be strongly associated with the level of dermal elastosis.

Asunto(s)

Dermis/patología , Tejido Elástico/patología , Epidermis/patología , Envejecimiento de la Piel/patología , Proteína p53 Supresora de Tumor , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Dermis/química , Epidermis/química , Femenino , Glicosaminoglicanos , Humanos , Inmunohistoquímica , Modelos Logísticos , Masculino , Melaninas , Persona de Mediana Edad , Queensland , Factores Sexuales , Luz Solar/efectos adversos

RESUMEN

BACKGROUND: We have previously shown the detrimental effects of 19 sub-erythemal exposures to daily ultraviolet radiation (DUVR, which mimics non-extreme exposure conditions), delivered over 4 weeks to volunteers. This source had UVA (320-400 nm) to UVB (290-320 nm) irradiance ratio of 25, instead of that close to 10 that is typically the case with solar-simulated radiation (SSR) that represents summer global sunlight with a clear sky and quasi-zenith solar irradiance. OBJECTIVE: Here, we report on an extension of this previous study, in which we evaluated the photoprotection afforded by a broad-spectrum daily-care product with a low-sun protection factor (SPF 8, UVA-PF 7 and 3* rated UVA protection). We assessed cellular and molecular markers of photodamage that are relevant to skin cancer and photoageing. RESULTS: This study shows that biological effects of repeated exposure to DUVR can be prevented by a broad-spectrum daily-care product and that the level of protection afforded varies with the studied endpoint. CONCLUSION: Efficient daily UVR protection, as provided by a broad-spectrum daily-care product, is necessary to prevent the 'silent' sub-erythemal cumulative effects of UVR from inadvertent sun exposure.

Asunto(s)

Enfermedades de la Piel/prevención & control , Luz Solar/efectos adversos , Protectores Solares , Humanos , Enfermedades de la Piel/etiología

RESUMEN

BACKGROUND: Dopa-responsive dystonia (DRD), a movement disorder characterized by onset in early childhood and a dramatic response to low doses of levodopa, has been shown to be caused by a number of different mutations in the GCH1 gene. METHODS: We identified a South African family which presented with DRD in three family members. Polymerase chain reaction (PCR) primers were designed to span all six exons of GCH1 and the PCR products were screened for pathogenic mutations using direct sequencing. RESULTS: A novel non-sense mutation (c.233delT; p.I78fsX79) was identified in the DRD patients, which would produce a markedly truncated protein of only 78 amino acids. This mutation was also present in a number of asymptomatic family members. CONCLUSIONS: A novel non-sense mutation in the GCH1 gene can be associated with DRD and reduced penetrance in South African patients.

Asunto(s)

Codón sin Sentido , Distonía/genética , Adolescente , Adulto , Edad de Inicio , Anciano , Antidiscinéticos/uso terapéutico , Secuencia de Bases , Niño , Preescolar , Distonía/tratamiento farmacológico , Exones , Familia , Femenino , Humanos , Levodopa/uso terapéutico , Masculino , Persona de Mediana Edad , Linaje , Sudáfrica , Adulto Joven

RESUMEN

The most common mutation associated with aminoglycoside-induced deafness is A1555G and it has been found in diverse populations worldwide. In the present study we investigated a large South African family known to harbour A1555G. A total of 97 family members were genotyped using the SNaPshot technique and 76 were found to be A1555G-positive (on haplogroup L0d) and are therefore at risk of developing irreversible hearing loss. The method worked equally well on both blood (from adults) and buccal swabs (from children). Variants in the tRNA(Ser(UCN)), A10S in TRMU and 35delG in GJB2 genes were shown not to act as genetic modifiers in this family. It is important to identify mutation-positive individuals and inform them of their increased risk of developing aminoglycoside-induced deafness especially in a setting like South Africa where these drugs are still commonly used because of their efficacy and cost-effectiveness as a treatment for resistant forms of tuberculosis.

Asunto(s)

Aminoglicósidos/efectos adversos , Antibacterianos/efectos adversos , Conexinas/genética , Análisis Mutacional de ADN/métodos , ADN Mitocondrial/genética , Sordera/genética , Pruebas Genéticas/métodos , Conexina 26 , Sordera/inducido químicamente , Predisposición Genética a la Enfermedad , Haplotipos/genética , Humanos , Proteínas Mitocondriales/genética , Mutación , Linaje , Sudáfrica , ARNt Metiltransferasas/genética

RESUMEN

Ageing, or increased mortality with time, coupled with physiologic decline, is a nearly universal yet poorly understood biological phenomenon. Studies in model organisms suggest that two conserved pathways modulate longevity: DNA damage repair and Insulin/Igf1-like signalling. In addition, homologs of yeast Sir2--the sirtuins--regulate lifespan in diverse organisms. Here, we focus on one particular sirtuin, SIRT6. Mice lacking SIRT6 develop a degenerative disorder that in some respects mimics models of accelerated ageing [Cell (2006) 124:315]. We discuss how sirtuins in general and SIRT6 specifically relate to other evolutionarily conserved pathways affecting ageing, and how SIRT6 might function to ensure organismal homeostasis and normal lifespan.

Asunto(s)

Envejecimiento/metabolismo , Reparación del ADN/fisiología , Fenotipo , Sirtuinas/metabolismo , Animales , Longevidad , Ratones , Ratones Noqueados , Modelos Biológicos

RESUMEN

Immunosuppression for therapeutic reasons (e.g. post transplantation, post chemotherapy), as well as pathologic immunodeficiency due to certain pathologic conditions (e.g. AIDS, leukemia), is increasingly encountered in daily medical practice. As a result, the concomitant risk for opportunistic infections is higher and immunocompromised patients may present with uncommon clinical and radiologic conditions. We report on a case of a 33-year-old immunocompromised woman with a history of recurrent T-cell lymphoblastic lymphoma, which presented with abdominal pain. Computed tomography (CT) images demonstrated significant small bowel dilatation, wall thickening, and high-density intestinal content, with a focal point of transition in the pelvis. Extensive fungal enteritis due to Candida Albicans with partial small bowel obstruction was found on autopsy.

Asunto(s)

Candidiasis/diagnóstico , Huésped Inmunocomprometido , Obstrucción Intestinal/microbiología , Enfermedades del Yeyuno/microbiología , Infecciones Oportunistas/diagnóstico , Adulto , Enteritis/microbiología , Resultado Fatal , Femenino , Humanos , Obstrucción Intestinal/diagnóstico , Obstrucción Intestinal/patología , Enfermedades del Yeyuno/diagnóstico , Enfermedades del Yeyuno/patología , Linfoma de Células T/tratamiento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamiento farmacológico

RESUMEN

Two double-blind studies versus vehicle were carried out to investigate the effects of a topically applied retinol plus vitamin C combination on epidermal and dermal compartments of aged or photoaged human skin. The two studies were performed on postmenopausal women who were selected for treatment based on the mild level of elastosis of their facial skin. At completion of treatment, skin biopsies were collected and processed for classical histology and immunohistochemistry. In the first study (aged skin), 8 volunteers applied the retinol- and vitamin C-containing preparation on the ventral side of one elbow and the vehicle on the other elbow twice daily for 3 months. After the 3-month treatment we observed histological changes mainly within the epidermis. The stratum corneum was thinner with a compact pattern, whereas the epidermal proliferation increased, resulting in a thickening of the viable epidermis. Moreover, the interdigitation index was increased. In the second study (photoaged skin), 11 volunteers were divided in two groups; one applied the retinol- and vitamin C-containing preparation and the other one the vehicle on their face twice daily for 6 months. Facial skin samples presented histologic hallmarks of photoaging, i.e. accumulation of elastotic material in the papillary dermis. After the 6-month topical treatment, the observed histological changes were mainly concentrated at the dermal level. Both treated and control groups showed the same distribution pattern of type I procollagen, however, the high level of type III procollagen originally observed in photoaged skin was reduced in the retinol- and vitamin C-treated group, resulting in a lower type III-to-type I procollagen ratio. Furthermore, a wide band of eosinophilic material just beneath the epidermis, devoid of oxytalan fibers and forming the 'grenz zone', appeared more frequently and was larger in the retinol- and vitamin C-treated group. In conclusion, our results show that repeated topical application of a preparation containing both retinol and vitamin C is able to reverse, at least in part, skin changes induced by both chronologic aging and photoaging.

Asunto(s)

Administración Cutánea , Ácido Ascórbico/administración & dosificación , Combinación de Medicamentos , Inmunohistoquímica/métodos , Envejecimiento de la Piel/efectos de los fármacos , Envejecimiento de la Piel/patología , Vitamina A/administración & dosificación , Ácido Ascórbico/química , Ácido Ascórbico/farmacocinética , Ácido Ascórbico/uso terapéutico , Biopsia , Esquema de Medicación , Evaluación de Medicamentos/métodos , Codo/patología , Cara/patología , Dermatosis Facial/tratamiento farmacológico , Dermatosis Facial/etiología , Dermatosis Facial/patología , Femenino , Humanos , Persona de Mediana Edad , Posmenopausia , Piel/efectos de los fármacos , Piel/patología , Piel/ultraestructura , Luz Solar/efectos adversos , Factores de Tiempo , Vitamina A/química , Vitamina A/farmacocinética , Vitamina A/uso terapéutico

RESUMEN

Nijmegen breakage syndrome is a disease characterized by immunodeficiency, genomic instability, and cancer susceptibility. The gene product defective in Nijmegen breakage syndrome, p95, associates with two other proteins, MRE11 and RAD50. Here we demonstrate that in the absence of DNA damage, a portion of p95 and MRE11 is concentrated in PML nuclear bodies (NBs); MRE11 localization to the NBs is p95-dependent. In mammalian meiocytes, these proteins are specifically found at the telomeres. These results implicate the NBs in the maintenance of genomic stability and suggest that p95 and MRE11 may have roles in telomere maintenance in mammals, analogous to the role their homologues play in yeast.

Asunto(s)

Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Endodesoxirribonucleasas , Exodesoxirribonucleasas , Proteínas Fúngicas/metabolismo , Neutrófilos/metabolismo , Proteínas Nucleares , Proteínas de Saccharomyces cerevisiae , Telómero/metabolismo , Animales , Línea Celular , Núcleo Celular/metabolismo , Fibroblastos/metabolismo , Técnica del Anticuerpo Fluorescente , Humanos , Meiosis , Ratones , Mutación

RESUMEN

Werner's syndrome (WS) is a human disease with manifestations resembling premature aging. The gene defective in WS, WRN, encodes a DNA helicase. Here, we describe the generation of mice bearing a mutation that eliminates expression of the C terminus of the helicase domain of the WRN protein. Mutant mice are born at the expected Mendelian frequency and do not show any overt histological signs of accelerated senescence. These mice are capable of living beyond 2 years of age. Cells from these animals do not show elevated susceptibility to the genotoxins camptothecin or 4-NQO. However, mutant fibroblasts senesce approximately one passage earlier than controls. Importantly, WRN(-/-);p53(-/-) mice show an increased mortality rate relative to WRN(+/-);p53(-/-) animals. We consider possible models for the synergy between p53 and WRN mutations for the determination of life span.

Asunto(s)

ADN Helicasas/genética , Esperanza de Vida , Mutación , Proteína p53 Supresora de Tumor/genética , 4-Nitroquinolina-1-Óxido/metabolismo , Animales , Western Blotting , Camptotecina/metabolismo , División Celular , Células Cultivadas , Senescencia Celular , Clonación Molecular , Relación Dosis-Respuesta a Droga , Embrión de Mamíferos/metabolismo , Exodesoxirribonucleasas , Fibroblastos/metabolismo , Biblioteca de Genes , Ratones , Ratones Noqueados , Datos de Secuencia Molecular , Fenotipo , Quinolonas/metabolismo , RecQ Helicasas , Bazo/metabolismo , Factores de Tiempo , Distribución Tisular , Helicasa del Síndrome de Werner

RESUMEN

Bloom syndrome (BS) is characterized by genomic instability and cancer susceptibility caused by defects in BLM, a DNA helicase of the RecQ-family (J. German and N. A. Ellis, The Genetic Basis of Human Cancer, pp. 301-316, 1998). RecQ helicases and topoisomerase III proteins interact physically and functionally in yeast (S. Gangloff et al., Mol. Cell. Biol., 14: 8391-8398, 1994) and in Escherichia coli can function together to enable passage of double-stranded DNA (F. G. Harmon et al., Mol. Cell, 3: 611-620, 1999). We demonstrate in somatic and meiotic human cells an association between BLM and topoisomerase IIIalpha. These proteins colocalize in promyelocytic leukemia protein nuclear bodies, and this localization is disrupted in BS cells. Thus, mechanisms by which RecQ helicases and topoisomerase III proteins cooperate to maintain genomic stability in model organisms likely apply to humans.

Asunto(s)

Adenosina Trifosfatasas/metabolismo , ADN Helicasas/metabolismo , ADN-Topoisomerasas de Tipo I/metabolismo , Meiosis , Adenosina Trifosfatasas/genética , ADN Helicasas/genética , ADN-Topoisomerasas de Tipo I/genética , Regulación de la Expresión Génica , Humanos , RecQ Helicasas , Células Tumorales Cultivadas

RESUMEN

Werner Syndrome (WS) is a human genetic disorder with many features of premature aging. The gene defective in WS (WRN) has been cloned and encodes a protein homologous to several helicases, including Escherichia coli RecQ, the human Bloom syndrome protein (BLM), and Saccharomyces cerevisiae Sgs1p. To better define the function of WRN protein we have determined its subcellular localization. Indirect immunofluorescence using polyclonal anti-human WRN shows a predominant nucleolar localization. Studies of WRN mutant cells lines confirmed the specificity of antibody recognition. No difference was seen in the subcellular localization of the WRN protein in a variety of normal and transformed human cell lines, including both carcinomas and sarcomas. The nucleolar localization of human WRN protein was supported by the finding that upon biochemical subcellular fractionation, WRN protein is present in an increased concentration in a subnuclear fraction enriched for nucleolar proteins. We have also determined the subcellular localization of the mouse WRN homologue (mWRN). In contrast to human WRN protein, mWRN protein is present diffusely throughout the nucleus. Understanding the function of WRN in these organisms of vastly differing lifespan may yield new insights into the mechanisms of lifespan determination.

Asunto(s)

Nucléolo Celular/metabolismo , ADN Helicasas/metabolismo , Síndrome de Werner/metabolismo , Animales , Exodesoxirribonucleasas , Técnica del Anticuerpo Fluorescente Indirecta , Células HeLa , Humanos , Ratones , RecQ Helicasas , Helicasa del Síndrome de Werner

RESUMEN

The 'Safe Sun' program had the goal of increasing patrons' and lifeguards' skin-protective behaviors and involved informational, prompting, feedback and goal-setting and incentive components coupled with pool lifeguards modeling protective behaviors such as wearing shirts, hats and sunglasses or staying in shaded areas. During two phases of a project involving 27 pools, it was found that while the program increased patrons' and lifeguards' protective behaviors, the largest changes were found at one pool where lifeguards were required to participate in the program. Patrons' protective behaviors at this pool increased from 30.7 percent to 52 percent, and lifeguards' protective behaviors increased from 40.8 percent to 95.7 percent. Social marketing, environmental change and institutionalization processes are needed to make skin-cancer prevention programs more effective.

Asunto(s)

ADN Helicasas/genética , Síndrome de Werner/genética , Envejecimiento/fisiología , Clonación Molecular , ADN Helicasas/química , Exodesoxirribonucleasas , Humanos , RecQ Helicasas , Homología de Secuencia de Aminoácido , Síndrome de Werner/fisiopatología , Helicasa del Síndrome de Werner

RESUMEN

All-trans retinoic acid (RA) has been shown to enhance subepidermal repair in photoaged hairless mice. The current study assesses the effects of RA on the glycosaminoglycan (GAG) content in irradiated and nonirradiated mouse skin. Mice were exposed to ultraviolet B (UVB) for 10 wk, after which they were treated either with 0.05% RA or with an ethanolpolyethylene glycol 400 vehicle three times a week for 10 or 20 wk. When assessed at the end of 10 wk of UVB irradiation, the GAG content had doubled, without a change in the hyaluronic acid (HA) to dermatan sulfate (DS) ratio. When irradiation was discontinued, the GAG content decreased progressively until the end of the experimental period. This decline was totally inhibited by RA treatment and could be ascribed to a marked increase in hyaluronic acid (78%), whereas no significant change in DS was observed. In nonirradiated skin, however, topical RA increased GAG levels mainly by a pronounced increase in the content (50%) and the synthesis (40%) of DS. In untreated mice, the HA/DS ratio decreased significantly with age in both irradiated and nonirradiated mice. Interestingly, RA maintained this ratio only in animals exposed to UVB. In addition, there was a marked stimulation in the heparin content, up to approximately 20-fold, after irradiation, whereas the amount of heparin in both irradiated and nonirradiated skin increased about 2- to 3-fold with RA treatment. In summary, the alterations induced in HA and DS contents in irradiated and nonirradiated skin indicate the specificity of the RA-induced effects for the various GAGs.

Asunto(s)

Dermatán Sulfato/metabolismo , Ácido Hialurónico/metabolismo , Piel/efectos de los fármacos , Piel/metabolismo , Tretinoina/farmacología , Animales , Femenino , Glicosaminoglicanos/biosíntesis , Glicosaminoglicanos/metabolismo , Heparina/metabolismo , Ratones , Ratones Pelados , Piel/efectos de la radiación , Rayos Ultravioleta/efectos adversos

RESUMEN

Although submaximal cycle ergometry testing (CET) can provide a good estimate of an individual's physical fitness, anticipatory heart rate increases accompanying pre-test anxiety can negatively affect the outcome of a submaximal CET. The present study evaluated the efficacy of a low-cost, technician-administered anxiety reduction intervention in the natural setting to reduce false-positives by removing heart rate feedback, and offering cognitive distraction and controlled breathing techniques. There were consistent findings for removing heart rate (HR) feedback and offering relaxation and distraction techniques on increasing the passing rate and decreasing HR at minute 1. Furthermore, when evaluated by gender, this minimal intervention also had an effect on increasing VO2max estimates, decreasing average HR, and increasing the passing rate for the female subjects. Interestingly, there were no effects found for any of the treatment conditions for the male subjects. The intervention's implications and future research directions are discussed.

Asunto(s)

Prueba de Esfuerzo/métodos , Prueba de Esfuerzo/psicología , Ansiedad , Reacciones Falso Positivas , Femenino , Frecuencia Cardíaca , Humanos , Masculino

RESUMEN

College students are engaging in high rates of behavior related to risk of infection from Human Immunodeficiency Virus (HIV) and other sexually transmitted diseases (STDs). A cognitive-behavioral skills training program for heterosexual college females focused on sexual assertiveness skills and the reduction of risk-related behaviors was designed and evaluated compared with an education-only program. Participants completed pre-intervention, post-intervention, and one-month follow-up assessments of: (a) HIV/STD-related knowledge and beliefs; (b) sexual, alcohol, and drug-related behaviors; and (c) sexual assertiveness role-plays. Skills training participants compared to education-only participants scored higher on sexual assertiveness skills, specific knowledge of HIV infection, and self-efficacy to perform lower risk sexual behaviors and reported a reduction in risk-related behaviors at post-intervention and follow-up assessments. The effectiveness of behavioral skills in HIV risk-reduction programs for college students is discussed.

Asunto(s)

Identidad de Género , Infecciones por VIH/prevención & control , Educación en Salud , Adolescente , Adulto , Asertividad , Terapia Cognitivo-Conductual , Condones , Femenino , Infecciones por VIH/psicología , Infecciones por VIH/transmisión , Conocimientos, Actitudes y Práctica en Salud , Humanos , Factores de Riesgo , Desempeño de Papel , Conducta Sexual , Resultado del Tratamiento

RESUMEN

This study assessed the effects of frequency of prompting (phone calls once a week versus once every 3 weeks) and structure of prompting (high versus low structure) in 135 participants (132 women and 3 men) in a walking program designed to meet the American College of Sports Medicine's cardiovascular exercise goals. Survival analysis using 6 months of data points and using the criteria of walking at least 20 min a day for at least 3 times per week indicated an effect for more frequent versus less frequent prompting (46% and 13%) but not for high- versus low-structure prompting (30% and 31%). The results suggested the efficacy of frequent prompting delivered in inexpensive ways as a means to increase exercise adherence and the further parametric study of other basic behavior change strategies.

Asunto(s)

Promoción de la Salud , Motivación , Refuerzo en Psicología , Caminata/psicología , Adulto , Retroalimentación , Femenino , Estudios de Seguimiento , Humanos , Control Interno-Externo , Masculino , Persona de Mediana Edad , Aptitud Física

RESUMEN

B7 delivers a costimulatory signal through CD28, resulting in interleukin-2 secretion and T cell proliferation. Blockade of this pathway results in T cell anergy. The in vivo role of B7 was evaluated with B7-deficient mice. These mice had a 70 percent decrease in costimulation of the response to alloantigen. Despite lacking B7 expression, activated B cells from these mice bound CTLA-4 and GL1 monoclonal antibody, demonstrating that alternative CTLA-4 ligand or ligands exist. These receptors are functionally important because the residual allogenic mixed lymphocyte responses were blocked by CTLA4Ig. Characterization of these CTLA-4 ligands should lead to strategies for manipulating the immune response.

Asunto(s)

Antígenos de Diferenciación/metabolismo , Linfocitos B/inmunología , Antígeno B7-1/inmunología , Inmunoconjugados , Linfocitos T/inmunología , Abatacept , Animales , Antígenos CD , Antígenos de Diferenciación/inmunología , Antígeno B7-1/genética , Antígeno B7-1/metabolismo , Secuencia de Bases , Antígeno CTLA-4 , Línea Celular , Interleucina-2/metabolismo , Isoantígenos/inmunología , Activación de Linfocitos , Prueba de Cultivo Mixto de Linfocitos , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Noqueados , Datos de Secuencia Molecular , Mutación , Transfección

RESUMEN

CTLA-4 is an adhesion receptor expressed on activated T cells. The amino acid sequence of CTLA-4 is related to CD28, and although the function of CTLA-4 remains unknown, it shares several features with CD28, including a common counter-receptor, B7, that is present on Ag-presenting cells. In a recent study we found that CD28 and CTLA-4 were coexpressed at the mRNA level on activated T cells but that only CD28 was expressed on resting T cells. Here we show that within the T cell population, CTLA-4 expression is restricted to the subset of T cells that also express cell surface CD28. CTLA-4 mRNA expression can be induced on quiescent T cells via phorbol ester-mediated activation of protein kinase C but not with calcium ionophore treatment alone. Phorbol ester-induced expression of CTLA-4 mRNA could be enhanced with calcium ionophore treatment, and treatment of cells in this manner resulted in a reciprocal decrease in expression of CD28 mRNA. Ligation of CD28 with monoclonal antibody also resulted in the specific and rapid induction of CTLA-4 mRNA. To study the expression of CTLA-4 at the protein level, a rabbit antiserum against a recombinant protein derived from CTLA-4 cDNA was generated. When activated T cells were labeled with [35S]methionine, the rabbit antiserum precipitated a 41- to 43-kDa protein from whole cell lysates. Similar results were found when detergent-soluble lysates from 125I surface-labeled resting and activated T cells were analyzed by SDS-PAGE. Surprisingly, under the conditions tested, CTLA-4 migrated primarily as a monomer at the cell surface, and could not be shown to exist as a disulfide-bonded homodimer or as a heterodimer consisting of CTLA-4 and CD28. These results suggest that B7 can bind to T cells via distinct receptor complexes consisting of either CD28 or CTLA-4, and that these complexes may potentially mediate distinct biologic functions. Further, the present results suggest that noncovalent interactions might mediate association of CTLA-4 and/or CD28 at the cell surface.

Asunto(s)

Antígenos de Diferenciación/genética , Expresión Génica , Inmunoconjugados , Linfocitos T/metabolismo , Abatacept , Animales , Antígenos CD/análisis , Antígenos de Diferenciación/análisis , Antígenos de Diferenciación/química , Antígenos de Diferenciación de Linfocitos T/análisis , Secuencia de Bases , Antígenos CD28 , Antígeno CTLA-4 , Línea Celular , Humanos , Sueros Inmunes/inmunología , Datos de Secuencia Molecular , ARN Mensajero/análisis , Conejos