While professional antigen-presenting cells (APCs) accounted for most of the human leukocyte antigen (HLA) gene expression (encoding MHC class II molecules), age-biased expression was driven by CAFs, vascular cells and cancer cells in older patients (Extended Data Fig. 6a), suggesting IFNγ exposure32 and aligning with enriched IFN response genes in these cells (Fig. 3b). This evidence concerns the gene IFNA1 and cancer.