Freund's adjuvant

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Freund's adjuvant is an antigen solution emulsified in mineral oil, used as an immunopotentiator (booster of the immune system). The so-called complete form (FCA) is composed of inactivated and dried mycobacteria, usually Mycobacterium tuberculosis (the pathogenic agent of tuberculosis). The so-called incomplete form (FIA) is the same adjuvant, but without the mycobacterial components. Named after Jules T. Freund (1890-1960), Hungarian-born American immunologist.

Freund's adjuvant is effective in stimulating cell-mediated immunity and may lead to the potentiation of the production of certain immunoglobulins, but this effect depends on the animal model used. Its use in humans is forbidden, due to its toxicity. Even for animal research there are currently guidelines associated with its use, due to its painful reaction and potential for tissue damage. Injections of FCA should be subcutaneous or intraperitoneal, because intradermal injections may cause skin ulceration and necrosis; intramuscular injections may lead to temporary or permanent muscle lesion, and intravenous injections may produce pulmonary lipid embolism.

When administered to mice, in some laboratory experiments Freund's complete adjuvant was said to have prevented juvenile-onset diabetes (Sadelain 1991) (Qin 1993) and combined with prepared spleen cells was said to have reversed it (Kodama 2003). In 2006 these claims were challenged by the findings of several other researchers (Couzin 2006). Although newspapers have described the 2006 findings as confirming the earlier experiments (Kolata 2006 March 25), in substantial ways they conflict with them.

The adjuvant is known to stimulate production of tumor necrosis factor, which is thought to kill the T-cells responsible for the autoimmune destruction of the pancratic Beta cells. Still in question is whether the regrowth of functional insulin-producing cells occurs due to differentiation and proliferation of existing pancreatic stem cells, or whether the injected spleen cells re-differentiate to an insulin producing form. Denise Faustman, whose work has been central to developing the protocol, has suggested that both mechanisms may play a role. However, in experiments to verify and examine her work, (Suri 2006) reported that DNA-based evidence yielded no sign of spleen cell derivatives in pancreatic islet Beta cells analyzed after treatments.