The reconversion of S-sulfonated antitetanus γ-globulin (S-GG) into the original γ-globulin was studied. S-sulfonate groups in S-GG could be converted into disulfide bonds in vitro. The conversion restored the greater part of both complement-fixing and skin-sensitizing activities. S-GG administered intravenously formed interchain disulfide bonds again in vivo, which was accompanied by restoration of the C-dependent passive hemolytic activity. Intravenous injection of S-GG did not cause a significant decrease in serum complement level.

S-sulfonated γ-globulin (S-GG) was prepared by treating γ-globulin with sulfite and tetrathionate ions. About four interchain disulfide bonds were selectively cleaved to give S-sulfonate groups. Although the above treatment strongly suppresses anticomplementary activity and nonspecific skin reactivity, the resulting S-GG retains high antibody activity. Furthermore, S-GG was found to maintain satisfactory levels for prolonged periods in vivo. The physicochemical and antigenic analyses of S-GG suggest that the S-sulfonation induces structural modification only at restricted sites.