Dominant LOF mutations of STAT1 that suppress phosphorylation of Y701 in STAT1, strongly reduce IFN-γ response, and lead to mendelian susceptibility to mycobacterial diseases (MSMD) and osteomyelitis with already one affected allele, while the response to IFN-α and antiviral defense seems comparably unaffected34. This evidence concerns the gene STAT1 and Mendelian susceptibility to mycobacterial diseases.