*2.5. Single-Cell RNA Sequencing*

Freshly isolated cells, or in vitro cultivated MFB, were analyzed by using the Chromium Single Cell 5 kit (10× Genomics, Pleasanton, CA, USA), according to manufacturer's protocol. In detail, cells were resuspended at 500 cells per μL in sterile filtered cold PBS containing 0.1% BSA. The experiment was conducted for 5000 recovered cells. After, library generation sequencing was performed by Illumina sequencing on a NextSeq 550 (IZKF genomics facility of the RWTH Aachen University, Aachen, Germany) as detailed before [6]. Primary analysis was done by using an in-house pipeline based on "cellranger" (10× Genomics). Additional analysis was then performed by using the "Seurat" (v2.3.2) [7] package for R (v3.5) (https://www.r-project.org/). Cluster identification was based on the 50 most significant principal components.
