TLR9 and infection: It is suggested that the downregulation of Tlr9 suppresses the release of Ifnα [31] and therefore Ifnγ [32], which is important for the successful clearance of M. tb. Here we present evidence that the host downregulates Tlr9 gene expression after infection with R179NT M. tb, which is not observed in host cells infected with M. tb cultured in the presence of Tween 80.