Autoantibodies in sera from patients with multiple sclerosis directed against antigenic determinants in pituitary growth hormone-producing cells and in structures containing vasopressin/oxytocin.

We have reported previously that autoantibodies in sera from patients with multiple sclerosis (MS) were reactive with rat brain, including pituitary, and with swine pituitary in areas thought to contain peptides of the somatotropin family and/or vasopressin/oxytocin. We have now tested the same patient sera for their specificity to antigenic determinants which are common to animal and human peptides. Localization of the binding sites of the MS sera was demonstrated in rat pituitaries and brains using the double immunofluorescence staining method, employing anti-bovine somatotropin (STH), anti-ovine prolactin (PRL), anti-neurophysin I and II, anti-somatostatin, and anti-vasopressin as reference antibodies. In the pituitary, the positive MS sera reacted specifically with cells which were also reactive with anti-bSTH. In the brain, positivity of MS sera was mainly localized in structures reactive with anti-neurophysin I and II and anti-vasopressin. Absorption experiments, immunocytochemical model assays, and radioimmunoassays, however, did not show specific binding of the MS sera to any of the above-mentioned peptides. Therefore, while these data present additional evidence on the localization of the immunocytochemical reaction sites of the MS autoantibodies, they do not enable us to identify the specificity of these antibodies.