The discovery of bi-allelic mutations in the RORC (retinoic-acid-related orphan receptor C) gene in patients with candidiasis and mycobacteriosis has revealed the pivotal role of RORC in mucocutaneous immunity to Candida and in systemic immunity to Mycobacterium in humans. Inborn errors of human IL-17 immunity underlie chronic mucocutaneous candidiasis (CMC), which is characterized by chronic or recurrent infections of the skin, nails, and oral and genital mucosae by Candida albicans, and inborn errors of human IFN-gamma immunity underlie Mendelian susceptibility to mycobacterial disease (MSMD), a rare congenital disorder characterized by susceptibility to infections by poorly virulent intracellular pathogens such as non-tuberculosis Mycobacterium. Five genetic etiologies of CMC and eighteen genetic etiologies of MSMD have been reported so far. Only a few patients were affected by both candidiasis and mycobacteriosis, including some patients with IL-12p40 and IL-12R-beta-1 deficiencies that impair both IFN-gamma immunity and IL-17 immunity. The new study was published online on July 9, 2015 in Science. The article is titled “Impairment of Immunity to Candida and Mycobacterium in Humans with Bi-Allelic RORC Mutations.” In an international collaboration study with St. Giles Laboratory of Human Genetics of Infectious Diseases at the Rockefeller University in New York City, researchers at Hiroshima University identified bi-allelic mutations in RORC, which encoded RORgamma (image) and RORgammaT, in seven patients from three kindreds of diverse ethnic origins, with an unusual combination of candidiasis and mycobacteriosis. RORgammaT is a well-known key transcription factor of Th17 cells, which produce IL-17 and IL-22.
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