Analysis of some immunochemical properties of human β-crystallin by radioimmunoassay

While radioimmunoassays for α- and γ-crystallin have been reported, this technology has not previously been applied successfully to the β-crystallins because of their instability to iodination by oxidative methods. We have succeeded in iodinating the human β-crystallins with the Bolton-Hunter reagent, a non-oxidative technique, and have developed radioimmunoassays for these proteins. Antisera to each of the three major classes of human β-crystallins were prepared and the feasibility of assaying the β₁, β₂ and β₃-crystallins individually by radioimmunoassay was investigated. Antisera to β₁ and β₃-crystallins were found to react equally well with all three β-crystallin antigens, suggesting that specific antigenic determinants may not be present in these fractions. In contrast β₂-crystallin was found to contain at least one highly specific antigen which can be detected as a minor precipitin band in immunodiffusion, but which appears to confer a high degree of specificity in the competitive binding situation of the radioimmunoassay. This apparent discrepancy between results from the two methods is discussed in terms of the marked differences in antibody concentration present.