Acinetobacter and E. coli lipopolysaccharide preparations comparative mitogenicity and induction in vitro of immunoglobulin synthesis in adult and neonatal pig lymphocytes.

Lipopolysaccharide (LPS) was prepared by phenol/water extraction of bacterial membranes prepared from Acinetobacter and Escherichia coli. The mitogenicity of laboratory-prepared LPS was significantly greater than that of commercial E. coli LPS for pig, sheep, calf and rat lymphocytes, assayed as [3H]-thymidine incorporation. Mouse lymphocytes responded well to commercial LPS and no greater response was obtained with other LPS preparations. A small proportion (14%) of the Acinetobacter LPS preparations was soluble in aqueous medium, the remainder comprising membraneous fragments of variable form and size. It is suggested that the insoluble presentation of LPS to cells may contribute to the improved mitogenicity compared with wholly soluble LPS. Acinetobacter LPS preparations were used to induce synthesis and secretion in vitro of immunoglobulin by adult blood lymphocytes and pre-suckled, neonatal spleen cells of the pig. IgM was the dominant class of immunoglobulin secreted. This work thus demonstrated that virgin, unprimed B cells could be induced into immunoglobulin secretion by mitogen stimulation.