THE IMMUNOHISTOCHEMICAL COMPOSITION OF THE HUMAN CORNEAL BASEMENT-MEMBRANE

Frozen sections of human cornea and conjunctiva were stained by immuno fluorescence and immunoperoxidase methods with a panel of antibodies a gainst various basement membrane (BM) and extracellular matrix protein s to study the composition of the human corneal BM. Laminin (Ln) immun oreactivity was detected in the BMs of the blood vessels and conjuncti val, limbal, and corneal epithelia by using a polyclonal antiserum and monoclonal antibodies (MAbs) against Ln chains alpha 1, beta 1, and g amma 1, but in the cornea the reaction with MAbs against alpha 1, beta 1, and gamma 1 chains was clearly weaker than in the other BMs and in some sections totally absent. Immunoreactivity to Ln alpha 2 chain wa s detected only in the BM of the limbus, whereas Ln beta 2 chain was d etected in the BMs of blood vessels and that of conjunctival and limba l epithelia. Ln-5 and Ln alpha 3 and beta 3 chains were seen in the BM s of the corneal, limbal, and conjunctival epithelia coaligning the in tegrin beta 4. Immunoreactivity for collagen type IV was lacking in th e BM of the corneal epithelium, but present in the BMs of the limbal a nd conjunctival epithelia as well as in the vascular BM. Collagen type VII immunoreactivity was seen in the BM areas of the corneal, limbal, and conjunctival epithelia. BMs of corneal, limbal, conjunctival, and vascular epithelia expressed fibronectin (Fn), including extradomain A cellular Fn and oncofetal cellular Fn isoforms, all lacking, however , extradomain B cellular Fn. The present results give new information on the Ln chain distribution and show that the BM of the corneal epith elium differs from that of surrounding epithelia by the lack of collag en type IV.