Chick "crooked-toe" syndrome induced by polar lipid in synovial fluids from some rheumatoid arthritis patients.

Injection into fertile chicken eggs of synovial fluids from some rheumatoid arthritis patients resulted in either embryo death or the development of the "crooked-toe" (CT) syndrome, or both, in newly hatched chicks. Synovial fluids from most RA patients (and fluids from a few non-RA individuals), however, were harmless. Dialyzing, partitioning, and gel filtration experiments indicated that the CT syndrome-inducing factor consists of 1 or more heat stable, dialyzable, polar lipids with molecular weights of about 3 to 4 x 10(3). Thin-layer chromatography revealed quantitative and qualitative differences between partially purified lipid preparations from "active" and "inactive" synovial fluids.