Susceptibility to tuberculosis (TB) in mice has recently been attributed to the IPR1 gene.  IPR1 is a member of the SP100/SP140 family of nuclear body proteins and encodes a leukocyte-specific nuclear body component. The protein can function as an activator of gene transcription and may serve as a nuclear hormone receptor coactivator. Alternative splicing has been observed for this gene and three transcript variants, encoding distinct isoforms, have been identified. SP110 is the closest homolog of the IPR1 protein in humans.  The IPR1/Sp110 gene product might play a role in integrating signals generated by intracellular pathogens with mechanisms controlling innate immunity, cell death, and pathogenesis.  IPR1/Sp110 is up-regulated after infection with M. tuberculosis and required by Anaplasma phagocytophilum for infection of human promyelocytic cells. Defects in Sp110 are a cause of severely impaired resistance to infection by M. tuberculosis.