RNF31 and lymphopenia: The first HOIP deficient patient was noted to have severe T cell defects, such as T cell lymphopenia especially affecting naïve T population and impaired response to T cell stimulations, consistent with previous reports of HOIP knockdown experiments in the Jurkat cells (16) and specific Rnf31 knock-in mice lacking the C-terminal half of the HOIP protein (17).