CD274 and tuberculosis: The theoretical possibility that monocyte surface PDL1 is related to TB bacillary load has been strengthened by observations such as reversal of PDL1 modulation with TB therapy, findings of significantly higher levels of PDL1 on pleural fluid derived monocytes as opposed to blood monocytes in patients with pleural TB [16], and experiments demonstrating modulation by intact mycobacteria on monocytes in-vitro [18].