This study evaluated the immunohistochemical expression of matrix metalloproteinases 2 (MMP2), 9 (MMP9), and interleukin-1 beta (IL-1β) in cardiac transplant patients, correlating their expression with acute cellular rejection (ACR), antibody-mediated rejection (AMR), inflammation, vasculitis, the Quilty effect, and immune markers. The gene discussed is MMP9; the disease is vasculitis.