Non-precipitating rabbit antibody to hapten: purification and properties.

Anti-azo benzene sulphonate antibodies were isolated from rabbit serum using two different methods in succession: first specific precipitation, and then specific absorption to a solid immunoadsorbent. The two purified preparations of antibody differed considerably in their ability to precipitate with antigen. It was found, however, that the non-precipitating antibody could largely be coprecipitated with antigen when mixed with precipitating antibody. Hapten binding experiments carried out on both preparations of antibody indicated that the κ values were of the same order of magnitude. The difference in method of preparation used was shown to have negligible effect on the hapten binding properties of the two antibodies. The important differences between the non-precipitating and precipitating antibodies were: (1) electrophoretic mobility, and (2) antigenic specificity. The precipitating antibody was identified as a γG-globulin, the non-precipitating variety as probably a γA-globulin. These results are compatible with the presence of a greater number of ionizable groups, i.e. potentially hydrophilic groups, on the non-precipitating antibody. The consequent higher molecular charge of the non-precipitating antibody may be an important factor in the failure of this antibody to precipitate with antigen.