LPS response during systemic Chlamydia infection

The overall study examines the mechanism and role of innate re-stimulation of T cells after activation and differentiation during infection. This particular study is focused on the restimulation of Th1 cells activated during Chlamydia infection, using in vivo LPS stimulation to increase the response. The study was conducted to compare the expression profile after LPS stimulation during Chlamydia infection to that seen after LPS stimulation during Salmonella infection (submitted as a separate dataset). Six female C57BL/6 mice were infected iv with Chlamydia muridarum, then 7 days post-infection (at the peak of T cell activation) 3 of the 6 mice were injected iv with LPS. All of the mice were cervically dislocated 4 hours later, and the spleens were removed and flash frozen for mRNA extraction. The Affymetrix GeneChip 'Mouse Gene 1.0 ST Array' was used to compare mRNA expression in total splenocytes for all murine genes that were well-annotated at the time of GeneChip purchase (2012). Biological replicates were averaged within each group and the fold-change difference between the averages was assessed for statistical significance by dChip software to determine which genes were up- or down-regulated in the spleen after LPS stimulation during Chlamydia infection. Total RNA was DNase treated, quantified, and assessed for quality, then submitted to the UC Davis Microarray Core Facility for RNA processing, hybridization, chip scanning, and initial data processing