RESUMO
We investigated the early effects of low doses of ionizing radiation on the CD2 gene expression in normal human T lymphocytes in order to clarify if low-dose ionizing radiation has an enhancing and/or stimulatory effect on the immune response. The results indicate that even low doses of X-irradiation strongly enhance the appearance of CD2 antigen, both in PHA-stimulated and in resting T lymphocytes as demonstrated by a rosette assay or by immunofluorescence. Moreover, an accumulation of CD2 mRNA is observed in X-irradiated cells compared with non-irradiated, a fact that is attributed mainly to transcriptional activation of the CD2 gene and not to stabilization of preformed mRNA.
Assuntos
Antígenos CD2/metabolismo , Linfócitos T/efeitos da radiação , Antígenos CD2/genética , Células Cultivadas , Regulação da Expressão Gênica/efeitos da radiação , Humanos , RNA Mensageiro/metabolismo , Doses de Radiação , Linfócitos T/imunologia , Transcrição GênicaRESUMO
Thioguanine resistant CHO cells (HPRT-) were stably cotransfected with pSV2-gpt and pi H3-CD2 vectors using the calcium phosphate coprecipitation technique. The effects of single low doses of ionizing radiation were studied in a CD2+ CHO clone. The CD2+ phenotype responsible for binding sheep erythrocytes and rosette formation, was not affected by X-rays doses in the range 2-6 cGy. However, after 10 cGy of X-irradiation, 50% of the cells lost the CD2+ phenotype. These results suggest that this CD2+ clone might be a very sensitive indicator of very low X-ray doses. The implications of the phenotypic changes, observed after very low doses of irradiation, are discussed.
Assuntos
Antígenos CD/genética , Antígenos de Diferenciação de Linfócitos T/genética , Antígenos de Superfície/genética , Antígenos de Superfície/efeitos da radiação , Receptores Imunológicos/genética , Animais , Antígenos CD/efeitos da radiação , Antígenos de Diferenciação de Linfócitos T/efeitos da radiação , Antígenos CD2 , Células CHO , Células Clonais/efeitos da radiação , Cricetinae , Humanos , Hipoxantina Fosforribosiltransferase , Fenótipo , Doses de Radiação , Receptores Imunológicos/efeitos da radiação , Formação de Roseta , Linfócitos T/imunologia , TransfecçãoRESUMO
Interspecific cell hybrids between Chinese Hamster Ovary (CHO) and phytohaemagglutinin (PHA) stimulated human T lymphocytes were purified by preparative rosetting with sheep red blood cells (SRBC). The hybrid cell clone used in the present study consisted of cells containing a complete set of the 20 CHO chromosomes and one extra human chromosome, No 19. Hybrid cells constitutively expressed high levels of human CD2 surface receptor and formed multilayer rosettes with SRBC and human erythrocytes. In addition to CD2 they produced low levels of a small number of human extracellular proteins. These findings suggest that the factor(s) responsible for CD2 expression are produced by the hybrid and that genes responsible for CD2 expression are located on chromosome 19. However, the present work cannot exclude that material of chromosome 1, where the CD2 gene has been assigned previously, is integrated somewhere in the hybrid karyotype. Further work is needed to clarify this point.
Assuntos
Antígenos de Diferenciação de Linfócitos T/genética , Cromossomos Humanos Par 19 , Receptores Imunológicos/genética , Linfócitos T/imunologia , Animais , Antígenos CD/genética , Antígenos de Diferenciação de Linfócitos T/análise , Antígenos de Superfície/genética , Southern Blotting , Antígenos CD2 , Células CHO , Células Clonais , Cricetinae , DNA/genética , Sondas de DNA , Imunofluorescência , Expressão Gênica , Humanos , Células Híbridas/imunologia , Immunoblotting , Imunodifusão , Cariotipagem , Ativação Linfocitária , Fenótipo , RNA/genética , Receptores Imunológicos/análise , Mapeamento por Restrição , Formação de Roseta , Linfócitos T/fisiologiaRESUMO
We found that the formation of multilayer rosettes by transformed human blood lymphocytes after phytohemagglutinin (PHA) stimulation is correlated with conformational changes of the chromatin as seen by premature chromosome condensation (PCC). The frequency distribution of grades of PCC and multilayer rosette formation suggests that changes in chromatin are a prerequisite for rosette formation. Rosette formation was most pronounced for 24-h and 48-h cultures. Chromatin decondensation and rosette formation showed identical patterns. The possibility that multilayer rosette formation is directly dependent on conformational changes of chromatin is discussed.
