Effect of the aggregational state on the mitogenicity of lipoprotein from the outer membrane of Escherichia coli.

The effects of ultrasonication, electrodialysis, and centrifugation through sucrose gradients on the mitogenicity of the lipoprotein (LP) from the outer membrane of Escherichia coli were studied in several inbred mouse strains. LP is not readily soluble in aqueous solution. By ultrasonication for 1 minute we obtained LP aggregates which were fully mitogenic; prolonged sonification had no influence on activity. Solubilization in 4% sodium dodecyl sulphate (SDS) and centrifugation into sucrose gradients yielded different aggregation forms of LP, which were B-lymphocyte mitogens towards LPS non responder C3H/HeJ mouse splenocytes, and towards congenitally athymic nude mice. By electrodialysis, LP could be transformed into different salt forms. The TEA-salt of LP exhibited enhanced mitogenicity. The results suggest that the mitogenicity of lipoprotein is widely independent from the aggregational state in which it is offered to the cells.