Fig. 6.

Is the PE25/PPE41 complex involved in quorum sensing of the immune system? A schematic representation of the likely role of the secreted PE25/PPE41 complex on the host immune system. The secretion of the PPE41 or PE25/PPE41 complex is mediated by Type VII secretion system. The PPE41 or the PE25/PPE41 protein complex is secreted outside by the bacterium, which could be recognized by host immune system. But the proteins may help the bacterium by sensing the strength of the host immune system. Weak immune system may induce these proteins to regulate their own expression or signal for multiplication of the bacteria to spread outside the cells by inducing direct lysis of macrophages via necrosis, which in turn helps the bacterium to multiply and spread infection in the surrounding cells resulting into disease reactivation.