Furthermore, GNLY and PRF1 expression levels were also significantly lower in TB patients compared to TST+ and TST- individuals, which is consistent with published data [33,34] and might be explained by rapid consumption of both perforin and granulysin during active disease due to an ongoing effector immune response, or due to migration of the T cell subset responsible for its production [35]. This evidence concerns the gene PRF1 and tuberculosis.