The content of free SH groups (about 0.24) and labile S-S bonds (about 0.64) per mole human IgG can be differentially determined by the reaction with 5,5′-dithio(2,2′-dinitro)benzoate (DTNB) for 30 min and 24 h, respectively. Highly significant linear correlations were found between the number of labile S-S and the percentage of IgG₁, and the number of free SH and the percentage of IgG₂ of the total IgG fraction. It is concluded that the IgG₁ molecule contains one S-S bond which is opened during the 24 h interaction with DTNB by a disulfide exchange reaction. This was also confirmed by the investigation of pure monomeric IgG₁. The splitting of this bond does not alter molecular weight, antigenic properties or antigen binding activity, but reduces significantly the complement binding activity of IgG. On the other hand, one free SH group could be found in the IgG₂ molecule. Changes have been observed in SH and S-S levels of total IgG in patients with various malignant diseases that are to be explained by corresponding changes of the percentages of IgG₁ and IgG₂.

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4-Hydroxynonenal (HNE), a major aldehydic product of lipid peroxidation, is a chemoattractant for neutrophilic polymorphonuclear granulocytes in vitro. The question was studied, whether HNE is formed during the ingress of neutrophils in the Sephadex model of inflammation. The polydextrane Sephadex G-200, which causes an acute aseptic traumatic inflammation, was injected subcutaneously into rats. The implants were excised 6-36 hours later, and the neutrophils separated from the exsudate by centrifugation. After extraction with dichloromethane HNE was identified in the exsudate by non-derivative reversed phase HPLC in combination with on-line uv-spectroscopy. The concentration of HNE in the inflammatory focus did not correlate with the number of neutrophils present. While the peak of HNE coincided with the time point of the highest turnover rate of neutrophils (0.13 microM at 6 hrs after implantation), the highest number of neutrophils (about 100 million cells) occurred not earlier than 18 hrs later (24 hrs after onset of inflammation). When neutrophils were isolated from the inflammatory focus and stimulated with Zymosan, they were able to produce HNE in vitro depending on the time of isolation. The highest production of HNE (0.17 microM) by phagocyting neutrophils was observed at the shortest inflammation time studied (3 hrs). In order to compare these results with the oxidative burst of neutrophils the formation of superoxide was also measured by the cytochrome c reduction assay in vitro. The maximum of the production rate of superoxide anion was observed at the same inflammation time (6 hrs), when the HNE maximum occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

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