Solubility properties of IgG immune complexes. Comparison between the effects of low molecular weight solvents and polyethylene glycols.

A systematic study of the influence of organic solvents on the interaction between human IgG and rabbit anti-human IgG IgG++ has been conducted, using difference turbidity and sucrose gradient centrifugation methods. It was found that very small alcohols like methanol and ethanol increased the turbidity signal, whereas larger alcohols (propanol, isopropanol, propanediol and ethylene glycol) had no influence on the signal. Sucrose, dioxane, dimethylformamide and dimethylsulphoxide decreased the difference turbidity signal. Sucrose gradient centrifugation did not show any influence. Polyethylene glycols were investigated with regard to molecular weights as well as concentrations. In contrast to the low molecular weight solvents, polyethylene glycols with molecular weights from 600 up to 20,000 gave a clearly expressed increase in the development of turbidity as well as in the size of the final turbidity signal. By sucrose gradient centrifugation, it was found that polyethylene glycols of molecular weights from 1000 to 10,000 had a profound effect on the solubility of immune complexes. The influence depended on the molecular weight as well as on the concentration. By use of [14C]-labelled polyethylene glycol it was found that polyethylene glycols did not form stable complexes with immune complexes. Furthermore, it was found that the zoning phenomenon was retained in the presence of small concentrations of polyethylene glycols, but higher concentrations of polyethylene glycols caused even antigen-excess complexes to show turbidity.