Immunohistochemical localization of NF-κB p65 in term and preterm fetal membranes and decidua. (A) Representative photomicrograph demonstrating characteristic p65 immunolabeling. In almost all cases, nuclear p65 labeling was absent in the amnion (Amn) and chorion (Chor), but prominent in the decidua (Dec). (B) Foci of nuclear p65 labeling were exceedingly rare in the amnion and absent in the chorion among all tissues examined. In both panels, arrows indicate areas of with nuclear p65 immunolabeling, while arrowheads demonstrate nuclei with deficient p65 labeling. Bars = 100 μm. (C) Box-and-whiskers plot of the p65 NLI in decidua from the following cohorts: preterm no labor (PNL, N = 22), spontaneous preterm labor (PTL, N = 21), term no labor (TNL, N = 23), and spontaneous term labor (STL, N = 21). NLI was calculated from a total of five micrographs per case, as selected using the targeted strategy described in the Methods section. The NLI in the TNL group was significantly less than that in the STL group (* P < 0.05, one-way ANOVA with Tukey's multiple comparison post hoc test).