TBCE and dry eye syndrome: To distinguish KCs from monocyte-derived macrophages (27), we used Clec4f as a specific marker for mouse KCs together with CD68 as a distinct marker combination for KCs, i.e. KCs stain Clec4f+/CD68+ whereas macrophages are Clec4f negative but CD68 positive and thus stain Clec4f-/CD68+.