Immunochemical characterization of a Mr 115 lens fiber cell-specific extrinsic membrane protein

Monoclonal and polyclonal antibodies have been produced against a lens fiber cell extrinsic membrane protein, with a relative molecular weight of approximately 115 kd. Enzyme Linked Immunosorbent Assays (ELISA) of retina, ciliary body-iris, liver, and skeletal muscle, utilizing these antibodies, suggest that the antigen is unique to the lens. Immunocytochemistry indicates that the antigen is present only in the differentiated fiber cell, and is absent from the lens epithelium. Further, immunocytochemical reactivity is predominantly associated with the fiber cell plasma membrane. However, sequential extraction of fiber cell homogenate, followed by quantitative, competitive ELISA analysis, indicates that most of the antigen is recovered in the neutral buffer extract. ELISA analysis using monoclonal antibodies indicates that an analogous antigen is present in human and rabbit lenses. On the basis of these results we characterize this antigen as a conserved extrinsic membrane protein, which is unique to the differentiated lens fiber cell. The relationship of this antigen to a previously described Mr 95 beaded filament-associated protein is discussed.