Sprouting inducing activity of human sera: low capacity in sera from patients with cranial polyneuropathy.

Cranial idiopathic acute peripheral facial nerve paralysis (Bell palsy) has been used as a model disease in the present study mainly to investigate trophic capacity of serum components. The ability to induce sprouting from chick embryo dorsal root ganglia was used as the bioassay for trophic activity. Sera from normal patients induce neuritic outgrowth from dorsal root ganglia of chick embryo in the absence of any exogenous factor. Sprouting, to a very limited extent or none, has been induced by 80% of the sera derived from the Bell palsy patients. Further analysis of the biochemical nature of the reduced activity has revealed that in sera of Bell palsy patients the substances that are fractionated within the Ig fraction are responsible for the reduced capacity to induce sprouting without loss of supportive molecules.