Studies on the optimal conditions of CSF generation by endotoxic LPS and its PS derivative in mice.

Not only the endotoxic LPS preparations, but a non-toxic, lipid-free, non-mitogenic hydrolytic breakdown product of it (called PS) is also capable of inducing colony stimulating factor (CSF) release (1). Due to difficulties to reproduce above findings it became necessary to study the optimal conditions to obtain CSF active PS preparations. It was found that the CSF generating component of the highly heterogeneous PS mixture is sensitive to acidic hydrolyses, but it is less sensitive than the toxic site in the lipid moiety of the LPS. Carefully controlled optimal hydrolytic conditions give PS preparations which have less than one percent residual endotoxicity but maintained 40 to 80% of the original CSF generating capacity. Prolonged hydrolysis will destroy this activity too. Optimal dose of LPS and PS for CSF induction in mice differed widely. For LPS the optimal dose is 25 micrograms, injecting more gave a much reduced or non-detectable CSF level. Optimal dose for PS was 160 micrograms, and this generated a significantly higher CSF level than 25 micrograms LPS. At concentrations below 25 micrograms, LPS was clearly more active than PS. The CSF level reached its peak at 3-4 hours after other LPS or PS injection. Intravenous route was sometimes but not always more effective than intraperitoneal.