TGFB1 and Peritoneal Fibrosis: Transforming growth factor beta (TGFB) is a predominant cytokine involved in the initiation and progression of peritoneal fibrosis.3, 4 Mesothelial cells secrete TGFB in response to injury from dialysis solutions and infection.4 TGFB has been observed to induce changes in peritoneal structure including thickening of the submesothelial zone and angiogenesis.