[Labile disulfide bonds and free thiol groups in human IgG. III. The "sigma S value" in gynecologic neoplasms].

The immunoglobulins G contain labile disulfide bonds which can easily be opened by dithionitrobenzoic acid in the subclass G1, and free SH groups in the subclass G2. The "sigma S value" is a photometrically determined quantitative measure of both groups added together. 57 cases of different gynaecological malignant tumours gave a mean sigma S value of 1.02 +/- 0.24 and 7 cases of stage 0 a sigma S of 1.05 +/- 0.25, whereas in 45 cases of benign diseases the sigma S was found to be 1.45 +/- 0,21. The difference between the values in the malignant and benign cases was highly significant (p less than 0.001). The sigma S in the benign cases lies within the normal range ascertained with healthy serum donors. These results are in accordance with results formerly obtained with malignant tumours in other locations. This leads us to the assumption that the shift in sigma S may be functionally and/or symptomatically associated with malignancy. The decrease in sigma S is interpreted in terms of a decrease in the percentage of subclass G1 in the total IgG.