Enhancement of allergic encephalomyelitis by particulate adjuvants inoculated long before antigen.

Carbonyl iron and several other particulate materials have been reported to enhance the development of experimental allergic encephalomyelitis when injected with neural antigen. In the present work, silicon and silica powders have been added to the list of particulate adjuvants. In addition, several particulate materials, but not carbonyl iron, were effective adjuvants when inoculated four weeks or even six months before the neural antigen. It was necessary for adjuvant and antigen to be injected in the same region, but both intraperitoneal and subcutaneous routes were effective. The long-lasting adjuvanticity of certain particulates in the tissues is probably related to their bland and unabsorbable nature. The reasons for restrictions in the range of adjuvants and antigens that are effective in this system and the possibility of a similar occurrence in nature remain to be investigated.