Anti-complementary action of polymorphic "solubility forms" of particulate inulin.

Inulin crystallizes in a series of polymorphic forms with different solubility rates, ranging from one instantly soluble at 23 degrees C (beta 0(23) inulin) through a form soluble at 37 degrees C with a half-time of 8 min (alpha 8(37) inulin) to a form virtually insoluble at 37 degrees C (gamma inulin). All forms are interconvertible, the more soluble and unstable progressing on standing to less soluble and more stable forms, only reversible by complete solution followed by recrystallization. The end product is the stable gamma inulin, only formed by polymers greater than 8000 mol. wt. A method is given for preparing pure "gamma inulin for injection", comprising insoluble ovoids of less than 1 micron diameter free of soluble inulin and endotoxin. An assay developed for complement action by the alternative pathway showed that gamma inulin was the most potent activator polymorph, more active than killed S. aureus and zymosan. Dissolved inulin and the more soluble polymorphs were inactive and in a mixture hindered alternative pathway activation by the gamma form.