ITGAM and keratoconus: Subsequent data have now demonstrated that most tissue macrophages arise from embryonic progenitors and are long-lived and self-renewing.[26, 27, 28, 34, 35] Two principal KC subsets have been described based on F4/80 and CD11b expression.[3, 4, 6] CD32 and CD68 have also been utilized to characterize KCs.[3, 5] However, CD32 is expressed on other cells, such as B cells.