Given the previous identification of GZMK-expressing T cells within inflamed synovial tissues of rheumatoid arthritis (RA) patients (49, 62) and the drastically increased incidence of BPH among RA patients (40, 49), we hypothesized that similar GZMK-expressing subsets would be present in both RA and aged prostate tissues, indicating a similar pro-inflammatory tissue microenvironment. This evidence concerns the gene GZMK and benign prostatic hyperplasia.