PTPRC and keratoconus: A significant increase in the proportions of total natural killer (NK) cells (CD45+CD66b−CD3−CD56+), CD56Low NK cells or cytotoxic NK cells (CD45+CD66b−CD3−CD56Low) and CD56High NK cells or increased cytokine-producing NK cells (CD45+CD66b−CD3−CD56High) was present in KC (across all grades) compared to controls (Fig. 2a–c).