TYPE-II COLLAGEN DURING CARTILAGE AND CORNEAL DEVELOPMENT - IMMUNOHISTOCHEMICAL ANALYSIS WITH AN ANTI-TELOPEPTIDE ANTIBODY

We have examined the pattern of immunoreactivity of a monoclonal antib ody, II-5B2, with specificity for an epitope which resides within the NH2-terminal extension peptide (telopeptide) of the avian type II coll agen molecule. This epitope is available in regions of matrix where de novo synthesis of the molecule is ongoing, but not where synthesis ha s ceased and maturation and crosslink formation have occurred. Within the cartilaginous growth plate, the epitope disappears from the matrix soon after the chondrocytes become hypertrophic; within the cornea, t he epitope disappears subjacent to the epithelium. The II-5B2 epitope is not made available by a variety of procedures shown to remove poten tially masking substances and to disrupt fibrillar organization. It is rendered available, however, when covalent crosslink formation betwee n collagen molecules is blocked through administration of beta-aminopr opionitrile or penicillamine. In contrast, the epitope of another mono clonal antibody against type II collagen, II-II6B3, which resides in t he triple-helical domain of the molecule, in cartilage is present thro ughout the growth plate including the hypertrophic zone, and in cornea extends for a considerable distance into the stroma. Thus, it is avai lable for antibody binding regardless of fibril maturation and crossli nking. These data suggest that the II-5B2 epitope becomes unavailable when the telopeptide becomes crosslinked. By using these two monoclona l antibodies in serial sections, one can establish the crosslinking pa ttern of type II collagen in the tissue. This set of antibodies is a p otentially useful tool for analyzing normal and abnormal development, remodeling, and repair processes in the skeletal system and in other t issues where type II collagen is involved in organization of the matri x, such as the primary corneal stroma.