RESUMEN
Patients harboring a malignant brain tumor have been described as being highly immunosuppressed, as evidenced by reduced numbers of T cells and the decreased ability of their lymphocytes to produce interleukin-2 (IL-2). In order to determine whether an intrinsic abnormality exists in the T lymphocytes of glioma patients and to evaluate what role corticosteroids may play in glioma-associated immunosuppression, in vitro T cell proliferative function in the presence of recombinant IL-2 (rIL-2) was examined in age-matched groups of normal control subjects, steroid-free patients with glial tumors, steroid-dependent patients with glial tumors, and steroid-dependent patients with nonglial cerebral tumors. The results demonstrated that, when enriched T cell populations of all brain-tumor patients were stimulated with rIL-2 and phytohemagglutinin (PHA), there were no statistically significant differences between any groups. In contrast, when T cell populations were stimulated with mitogenic combinations of phorbol ester, calcium ionophore, and rIL-2, those from steroid-dependent patients with glial tumors had a significantly lower response than those from normal control subjects, suggesting that a population of T cells capable of responding to phorbol ester/ionomycin and not PHA stimulation is inhibited by corticosteroid therapy in glioma patients. In addition, T cells of four brain-tumor patient/age-matched control subject pairs were stimulated with either phorbol ester/ionomycin or PHA for 24 hours; three of the four patients expressed low-affinity IL-2 receptor levels as high or higher than their respective control subjects, suggesting that IL-2 receptor expression in these patients may be quantitatively normal once the T cell number is corrected. Taken together, these results show that the decreased PHA responsiveness that has been previously reported in lymphocytes of glioma patients is not due to a cellular abnormality within the potentially responsive cells, but rather reflects the reduced proportion of T cells within their peripheral blood which, as a consequence, reduces the level of IL-2 production attained upon activation.
Asunto(s)
Neoplasias Encefálicas/inmunología , Glioma/inmunología , Tolerancia Inmunológica/inmunología , Activación de Linfocitos/inmunología , Linfocitos T/inmunología , Corticoesteroides/uso terapéutico , Adulto , Anciano , Femenino , Humanos , Tolerancia Inmunológica/efectos de los fármacos , Interleucina-2/farmacología , Ionomicina/farmacología , Activación de Linfocitos/efectos de los fármacos , Masculino , Persona de Mediana Edad , Forbol 12,13-Dibutirato/farmacología , Fitohemaglutininas/inmunología , Receptores de Interleucina-2/inmunología , Proteínas Recombinantes , Linfocitos T/efectos de los fármacos , Células Tumorales CultivadasRESUMEN
The analysis of translational efficiencies of specific mRNAs requires a determination of the polyribosome size. The appropriate value to use in such calculations is the number-average size. A method is described for accurately measuring the number-average size of total and of specific protein synthesizing polyribosomes using isokinetic sucrose density gradients and 125I-labeled antibodies. By this method, we demonstrated that albumin synthesizing polyribosomes from a serum albumin secreting mouse hepatoma cell line exist over a broad range from trimers to 20-mers (mean 6-10). The specificity of antibody interaction with polyribosomes was demonstrated using cells not synthesizing mouse serum albumin, and by demonstrating that 125I-anti ovalbumin does not bind to mouse hepatoma polyribosomes. Treatment of the mouse hepatoma cells with 1 MUM cycloheximide shifted practically all of the monomers into polyribosomes resulting in an increase in the number-average size of the albumin synthesizing polyribosomes. Cycloheximide treatment, however, did not eliminate the size heterogeneity in the albumin synthesizing polyribosomes.
Asunto(s)
Polirribosomas/ultraestructura , Albúminas/biosíntesis , Animales , Especificidad de Anticuerpos , Línea Celular , Centrifugación por Gradiente de Densidad , Cicloheximida/farmacología , Humanos , Ratones , Tamaño de la Partícula , Polirribosomas/efectos de los fármacos , Polirribosomas/inmunología , Biosíntesis de Proteínas , ARNRESUMEN
A method is described for the measurement of protein synthesis parameters in cultured cells. Ribosome transit times, polyribosome size distribution and relative synthetic rates are measured on individual cultures of cells. This method is applied to an analysis of cycloheximide (1 micrometer) inhibition of protein synthesis in cultured mouse hepatoma cells.