library_construction_protocol: Tissue pieces from the ovarian tumors were mechanically sissociated and single cell suspensions were prepared after debris removal. B cells were sorted using anti-human CD19 antibodies. The scRNA-Seq libraries were prepared following the protocol provided by the 10X genomics. The cDNA and ATAC-seq libraries were completed in a single bulk reaction using the 10X Genomics Chromium NextGEM Single Cell Multiome ATAC + Gene Expression Reagent Kit.  50,000 or 25,000 sequencing reads per cell for scRNA-seq or ATAC-seq libraries, respectively, were generated on dedicated Illumina NextSeq 500 sequencing runs according to the vendor protocol.