RESUMO
BACKGROUND AND OBJECTIVES: The pathogenesis of essential thrombocythemia (ET), a disease characterized by megakaryocyte hyperplasia and persistent thrombocytosis, is not completely clarified. Interleukin-6 (IL-6), one of the cytokines related to megakaryocytic development, exerts its effect through binding to a cell surface receptor, IL-6Ra, and a signal transducing unit, gp130. Interestingly, the soluble form of the IL-6Ra, IL-6sR, is an agonist for IL-6 activity. In order to evaluate the possible participation of IL-6sR in ET we measured its levels in plasma, platelets and in the supernatant of a mononuclear cell culture. We also evaluated IL-6R on leukocyte membrane and IL-6R/IL-6sR mRNA expression in mononuclear cells. DESIGN AND METHODS: Fifty-five patients with ET were evaluated. IL-6sR and IL-6 were measured by an ELISA technique. Mononuclear cells were cultured for 48 hr and IL-6sR released into the supernatant was measured. IL-6R on leukocyte surfaces was evaluated by flow cytometry. IL-6R and IL-6sR mRNA levels were assessed by semi-quantitative reverse transcription polymerase chain reaction. RESULTS: Plasma IL-6sR levels were increased while intraplatelet levels were low in untreated ET patients. Plasma levels decreased during treatment. Non-stimulated mononuclear cells from ET patients released greater amounts of IL-6sR than did cells from normal controls in 48-hour culture. No abnormality was found in IL-6R or IL-6sR mRNA expression by mononuclear ET cells. IL-6R on leukocyte surfaces was normal. INTERPRETATION AND CONCLUSIONS: Increased plasma IL-6sR levels might have a role in the abnormal megakaryocytic proliferation seen in ET patients, while platelets and mononuclear cells could be the source of the above-mentioned high levels of plasma IL-6sR.
Assuntos
Receptores de Interleucina-6/análise , Trombocitemia Essencial/sangue , Adulto , Idoso , Idoso de 80 Anos ou mais , Plaquetas/química , Células Cultivadas , Feminino , Humanos , Interleucina-6/sangue , Leucócitos Mononucleares , Masculino , Pessoa de Meia-Idade , RNA Mensageiro/análise , Receptores de Interleucina-6/sangue , Receptores de Interleucina-6/genética , Solubilidade , Trombocitemia Essencial/etiologiaRESUMO
El valor normal de plaquetas varía entre 150,000 y 450,000 x mm al cubo. Se define trombocitosis como un recuento mayor de 600,000. Pueden ser primarias, por un trastorno mieloproliferativo o secundarias a un gran número de patologías. Objetivos: conocer en nuestro medio la frecuencia de ambos tipos de trombocitosis, describir las patologías asociadas y relacionar la magnitud de la trombocitosis con los diferentes diagnósticos. Material y métodos: se analizaron 18,000 hemogramas realizados entre enero y diciembre de 1998, en el Hospital Roberto del Río. Se evaluó sexo, recuento de plaquetas y leucocitos, hematocrito, hemoglobina, VCM, CHCM y diagnósticos. Resultados: se encontró trombocitosis en 584 exámenes (3,24 por ciento). Se evaluaron 334 fichas, el 62 por ciento eran de sexo masculino. El 0,9 por ciento presentó cifras de plaquetas > 1,000,000 x mm al cubo (dos casos fueron trombocitosis primarias: trombocitemia esencial y leucemia mieloide crónica y un caso de meningitis bacteriana). Las trombocitosis secundarias se asociaron a: infecciones (48,8 por ciento), principalmente respiratorias, deficiencia de hierro (18,6 por ciento) y daño tisular (12,6 por ciento). Conclusiones: la frecuencia de trombocitosis en niños es baja. Cuando la trombocitosis es menor de 1,000,000 x mm al cubo debe sospecharse una etiología secundaria