Freund's adjuvants: relationship of arthritogenicity and adjuvanticity in rats to vehicle composition

Abstract

Over a hundred compounds and natural materials were examined for their ability to induce arthritis in rats when mixed with heat-killed delipidated Mycobacteria tuberculosis. Many of these materials were also assessed for (CMI) adjuvant activity by their ability to induce allergic encephalomyelitis (EAE) in rats when mixed with guinea-pig spinal cord, both with and without added M. tuberculosis.

Cyclization and/or the presence of oxygen atoms, or double bonds reduced (or abolished) the arthritogenic potential and adjuvanticity of alkanes>C₁₀. Esters/triglycerides of fatty acids >C₁₂, retinol acetate (not palmitate) and vitamins E and K showed co-arthritogenic and adjuvant activity. Other active lipids included squalene and cholesterol oleate, which are both present in human sebum. Sebaceous lipids may therefore perhaps function as natural adjuvants if resorbed during abrasion and infection.

Squalane (perhydrosqualene), pristane and hexadecane were excellent substitutes for mineral oil in preparing arthritogenic adjuvants from various mycobacteria, C. rubrum and N. asteroides. These oily compounds were also very effective adjuvants per se, in the absence of bacterial material or emulsifier, for inducing EAE in Lewis rats.