Organization of collagen types I and V in the embryonic chicken cornea: monoclonal antibody studies.

To determine whether type V collagen is antigenically masked in situ by its fibrillar organization, two different methods were used to perturb selectively the structure of collagen fibrils in sections of embryonic chicken corneas. The experimentally modified tissues were probed by immunohistochemical procedures with monoclonal antibodies against types V and I. A lathyritic agent was used to block crosslinking of newly synthesized collagen. This results in reversible temperature-sensitive alterations in fibrillar packing, such that freshly formed collagen fibrils retain their aggregated state at 37 degrees C but become dissociated upon cooling. Type V-specific immunofluorescence remained masked at 37 degrees C but was revealed at 0 degree C. The effect of temperature was partially reversible, indicating that type V collagen is normally unavailable for antibody binding because of its fibrillar arrangement. In sections of normal corneas, treatment with corneal collagenase, which degrades type I collagen, but not type V, also unmasked the latter. This implicates type I collagen as the masking agent. We propose that collagen types I and V are incorporated together in heterotypic fibrils.