47,XXY is found in excess among men with SLE. Men commonly have SLE that is more severe than that found among women, but the 47,XXY men had less severe SLE than other men.
About 90% of patients with systemic lupus erythematosus (SLE) are female. We hypothesize that the number of X chromosomes, not sex, is a determinate of risk of SLE. Number of X chromosomes was determined by single nucleotide typing and then confirmed by karyotype or fluorescent in situ hybridization in a large group of men with SLE. Presence of an sry gene was assessed by rtPCR. We calculated 96% confidence intervals using the Adjusted Wald method, and used Bayes’ theorem to estimate the prevalence of SLE among 47,XXY and 46,XX men. Among 316 men with SLE, 7 had 47,XXY and 1 had 46,XX. The rate of Klinefelter’s syndrome (47,XXY) was statistically different from that found in control men and from the known prevalence in the population. The 46,XX man had an sry gene, which encodes the testes determining factor, on an X chromosome as a result of an abnormal crossover during meiosis. In the case of 46,XX, 1 of 316 was statistically different from the known population prevalence of 1 in 20,000 live male births. A previously reported 46,XX man with SLE had a different molecular mechanism in which there were no common gene copy number abnormalities with our patient. Thus, men with SLE are enriched for conditions with additional X chromosomes. Especially since 46,XX men are generally normal males, except for infertility, these data suggest the number of X chromosomes, not phenotypic sex, is responsible for the sex bias of SLE.
Despite its overall simplicity, protein blotting or Western blotting has been proven to be a powerful procedure for the immunodetection of proteins, especially those that are of low abundance, following electrophoresis. The usefulness of this procedure stems from its ability to provide simultaneous resolution of multiple immunogenic antigens within a sample for detection by specific antibodies. Protein blotting has evolved greatly since its inception and researchers have a variety of ways and means to carry out this transfer. This procedure is used in combination with other important antibody-based detection methods such as enzyme-linked immunosorbant assay and immunohistochemistry to provide confirmation of results both in research and diagnostic testing. Specificity of antibodies used for immunohistochemistry is of critical importance and therefore Western blot is a "must" to address antibodies' specificity.
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