, 2011a), MICA expression on noninfected bystander cells in C. trachomatis-exposed cultures was unaffected. Further, we also demonstrated that active C. trachomatis infection is required for changes in ligand expression to occur, as these phenomena were not observed when cells were exposed to UV-inactivated EBs (Fig. 2b). These data clearly indicate distinct kinetics and effects of C. trachomatis on MHC class LBH589 supplier I and MICA and suggest that cytokines and/or chemokines released by infected host cells

do not influence MICA expression on neighboring cells. To assess the physiological consequences of C. trachomatis serovar D-mediated MHC class I and MICA modulation, mock-infected, UVEB-infected, and C. trachomatis-infected A2EN cells were

exposed to NK92MI cells in coculture experiments. NK92MI expresses NK2GD and KIR this website – receptors for MICA and MHC class I, respectively, (Fig. 3a). Similar to NK cells derived from peripheral blood mononuclear cells, these cells also contain the intracellular cytolytic granule proteins perforin and granzyme (Fig. 3b). Morphologic assessment of C. trachomatis-infected and mock-infected cocultures revealed that the majority of mock-infected cells retain normal A2EN monolayer morphology over 4 h of exposure (data not shown), while infected cells reveal morphologic evidence of cell lysis, including membrane blebbing (Video S1, Supporting information). Quantification of LDH release confirmed a significant increase in A2EN cell lysis among infected cells at 34 hpi

when compared to mock-infected control (P < 0.01), suggesting that C. trachomatis infection enhances the susceptibility of infected endocervical epithelial cell to NK cell cytolytic HAS1 activity (Fig. 4a). Pertinent to these observations, addition of a neutralizing anti-MICA antibody significantly decreased NK92MI lytic activity against C. trachomatis-infected cultures (P < 0.01). This indicates that the enhanced C. trachomatis-infected cell lysis by NK cells was dependent on MICA. Furthermore, no significant increase in susceptibility to NK cell lysis was observed in A2EN cells infected with UV-inactivated Chlamydial elementary bodies, supporting previous data that active C. trachomatis infection is required for the modulation of NK ligand expression to increase NK cell lysis. Interestingly, the differences in lysis of C. trachomatis-infected A2EN vs. mock-infected, UVEB-exposed and anti-MICA-treated targets are markedly greater at 34 hpi than at 42 hpi (Fig. 4). These data indicate that there is a significant decrease in the efficiency of lysis of C. trachomatis-infected A2EN cells at later time points postinfection (42 hpi) when compared to earlier stage infection (34 hpi) and suggest that the temporal modulation of MHC class I downregulation may impact the susceptibility of C. trachomatis-infected cells to NK cell lysis. Infected host cell lysis could result in the release of infectious or noninfectious chlamydial particles.