IL-6 can be produced by almost every immune cells and many non-immune cells including endothelial cells, fibroblasts and keratinocytes45, and KC is produced mainly by epithelial cells and endothelial cells48, 49, while TNF-α is secreted by immune cells, including macrophages, monocytes, neutrophils, T-cells (principally CD4+), and NK-cells50. The gene discussed is CD4; the disease is keratoconus.