“…Blood type ABO antigens have been detected primarily on epithelial cells. 9 Class 1 antigens (HLA-A, B, and C) are expressed by all nucleated cells in the body and are found on the corneal epithelium, stromal keratocytes, and endothelial cells. Class II antigens (HLA-DR, DQ, and DP) are present mainly on antigen-presenting cells such as macrophages and Langerhans cells.…”