Fig. 2.

Differential MHC class I and MICA expression on Chlamydia trachomatis-infected and uninfected, bystander A2EN endocervical epithelial cells. The expression of MHC class I and MICA were assessed in different populations of A2EN cells 38 hpi. (a) Uninfected bystander cells were delineated from C. trachomatis-infected cells based on Chlamydial-LPS-FITC positivity. Uninfected bystander cells were identified by setting the gate below the threshold of basal-FITC signals from uninfected cells (Chlamydia-negative, mock-infected control). Chlamydia trachomatis-infected cells were identified by gating for cells above the threshold FITC signal of the control. (b) The degree of change in MHC class I and MICA expression on A2EN exposed to UV-irradiated elementary bodies (UVEB) and those from bystander-uninfected cells and C. trachomatis-infected cells from an A2EN cell culture exposed to infectious EBs are presented as delta MFI values. The horizontal line represents the delta MFI of mock-infected cells and the degree of difference in MHC class I and MICA expression between the different A2EN cell groups and the mock-infected control is illustrated by the diversion from mock delta MFI = 0. Negative delta MFI values indicate a decrease in MHC class I expression, while positive delta MFI values indicate an increase in MICA expression; ‘delta MFI’ = 0.5 represents a 100% upregulation of the absolute MFI value (see Materials and methods for ‘delta MFI’ calculation). Statistical analyses were performed using Student’s t-test. Asterisks indicate a significant difference relative to the mock-infected control (*P < 0.5; **P < 0.01). Differences in MHC class I and MICA expression between bystander cells and C. trachomatis-infected cells were also tested. Delta MFIs shown in the graph are the means and standard deviations from three to six independent experiments.