Marilen Benner

B CELLS CONTRIBUTE TO DECIDUAL IMMUNITY 97 4 (Thermo Scientific) or Poly-HRP-goat-anti-mouse/rabbit/rat IgG (BrightVision, Duiven, the Netherlands) with permanent red. IHC staining was assessed microscopically (AxioImager M2; Zeiss, Sliedrecht, the Netherlands) and sections were photographed using a high resolution color camera for bright field microscopy (AxioCam 105 color, Zeiss). Images were assessed using ZEN blue edition version 2.3 (Zeiss). For IF staining, visualization was performed using the Opal seven-color IHC Kit (Akoya Biosciences) on the BOND RX IHC & ISH Research Platform (Leica Biosystems). All staining cycles contained heating steps in between cycles. Tissue sections were counterstained with DAPI and mounted in Fluoromount-G (SouthernBiotech). Images of stained slides were acquired using the Vectra (Vectra 3.0.4, PerkinElmer) and exported with inForm software (Version 2.4.8, Akoya Biosciences). All staining Abs are listed in order of application in Supplemental Table S2. Quantification and statistical analysis All statistical analysis was performed using GraphPad Prism 5 (La Jolla, CA, USA). All values represent mean percentages ± SEM (error bars). Kruskal-Wallis and post-hoc Dunn’s multiple comparison test (non-parametric) were performed to assess differences between mucosal isolates compared to peripheral blood as well as when assessing differences between mucosal tissues. Details on sample size and statistical outcomes can be found in the respective figure legends. ACKNOWLEDGEMENTS We thank all women who participated in this study and the staff of MildredHuis. We appreciate all help of Dr. Anita van der Zwan for helpful discussions to optimize placenta dissociation for phenotyping, Daan Zegers during processing, and Niklas Bruse and Rindert Hartman for assistance in data formatting. MB is supported by a junior researcher grant of the Radboud Institute for Molecular Life Sciences.