Corneal allografts fail to express Ia antigens [31]

Although the surface determinants encoded by class I genes of the major histocompatibility complex (murine K/D; human HLA-A/B/C) are expressed on virtually all nucleated cells, the molecular products of class II genes (murine I, human HLA-D/DR) are expressed only on B lymphocytes, macrophages, sperm and certain subsets of T lymphocytes, especially suppressor cells^1,2. Controversy exists concerning the expression of class II antigens on cells of the epidermis. On the one hand, Hammerling et al.³ and Frelinger et al.⁴ have used serological methods to detect Ia antigens on epidermal cells. On the other hand, fluorescein isothiocyanate-conjugated antisera have been used to show that human and guinea pig class II alloantigens are only expressed on Langerhans cells in the epidermis^5-7. Recently, Rowden et al.⁸ have convincingly demonstrated that Ia antigens are expressed exclusively on Langerhans cells within murine epidermis. We have now shown that cornea, which is an epidermal tissue devoid of Langerhans cells, does not express Ia antigens.