*2.3.4 Mast cells and eosinophils*

After infection of mast cells with Chlamydia, cytokines such as TNF-α and IL-4 are released. As a result of these cytokines opening tight junctions, infiltration of the airways with immune cells occurs. This situation has a negative effect on the spread of Chlamydia [60, 61].

Eosinophils secrete IL-4 in the upper genital tract during genital *C. trachomatis* infection. It has been reported that this cytokine indirectly promotes the proliferation of endometrial stromal cells. In addition, it is thought that IL-4 may regulate the development of Th2 immune response after *C. trachomatis* infection [62].

### **2.4 Cytokines of the innate immune response**

In various animal and human studies, it has been shown that proinflammatory cytokines such as TNF-α IL-8, IL-1, and GM-CSF are associated with the development of tissue damage during the innate immune response to *C. trachomatis* infection [27, 29].
