Immunolocalization of type XII collagen at the corneoscleral angle of the embryonic avian eye.

A monoclonal antibody specific for the chicken alpha 1 (XII) collagen chain was used to immunolocalize type XII collagen in the corneoscleral of 17-19-day-old chicken embryos. These immunofluorescence studies localized type XII collagen around the scleral cartilages and ossicles. There was also a striking positive staining in the scleral spur and stroma of the corneolimbus beneath the external scleral sulcus. By immunofluorescence the corneal stroma proper was found to be relatively poor in type XII collagen. Immunoblot analysis confirmed the relative absence of alpha 1(XII) in the corneal stroma and demonstrated the presence of a 240 -kD polypeptide representative of alpha 1(XII) in extracts of the corneoscleral angle. It was suggested that type XII collagen in the corneoscleral angle reinforces the collagenous matrix at specific sites which require high tensile strength.