**3.2 The** *Chlamydia pneumoniae* **(CP); virulence factors, the host cells of CP, and cytokine responses and target cell activation mechanisms triggered by the CP infection**

#### *3.2.1 Virulence factors of CP*


CP protein, which translocates some proteins that modulate cellular response [33]. The reactive oxygen species production in CP-infected macrophages are limited by upregulating of antioxidant enzyme systems such as superoxide dismutase (SOD) and γ-glutamylcysteine synthase (γ-GCS) thereby limits the bacteria killing ability of macrophages [34].

III.CP inhibits host cell apoptosis *via* signaling specific cascades in monocytes; pro-apoptotic proteins that stimulate apoptosis can be degraded by CP and release of apoptotic trigger cytochrome-c can be inhibited by CP and the caspase-3 activity is reduced [33, 35, 36]

All of these virulence factors of CP create an appropriate environment for replication and survival [32].
