Interaction of Protein Antigens and Antibodies

Summary

Experiments on the solubilization and dissociation of egg albumin-anti-egg albumin precipitates have been conducted with acid, alkali, salts, dodecyl sulfate, and urea and with combinations of these substances.

Alkaline buffers of pH 11.0 and higher at 2 C dissolved the egg albumin-anti-egg albumin precipitate. Electrophoretic examination of dissolved precipitates showed no dissociation of the precipitate at pH 11.15, approximately 17% dissociation at pH 11.7, and 100% dissociation at pH 12.3. Tests with egg albumin and isolated rabbit immune γ-globulin revealed that the immune γ-globulin was altered only slightly at pH 11.7 but that marked changes occurred at pH 12.3.

A mixture of 0.3 M KCNS and 2 M urea at pH 10.75 produced complete dissolution of egg albumin-anti-egg albumin precipitates: however, electrophoretic analysis revealed only approximately 5% dissociation under these conditions. Increase in the pH of the mixture resulted in changes in the egg albumin and immune γ-globulin as measured by survival tests.

Egg albumin-anti-egg albumin precipitates dissolved completely in acid buffers at pH 3.4 or lower. Electrophoretic evaluation of possible dissociation at pH 2.8–3.2 was not feasible because of the similar mobilities of the components in this pH range. Exposure of immune γ-globulin at pH 3.4 or less produced changes as evidenced by complex formation leading to increased precipitate formation following egg albumin addition.

The dependence of dissociation of egg albumin-anti-egg albumin precipitates upon conditions sufficiently drastic to cause changes in the antibody component of the precipitates when tested separately suggest that the forces responsible for the primary interaction of egg albumin and anti-egg albumin are of the same nature and magnitude as those responsible for maintaining the native configuration of the γ-globulin.