Thymopoietin and myasthenia gravis: neostigmine-responsive neuromuscular block produced in mice by a synthetic peptide fragment of thymopoietin.

Thymopoietin is the thymic hormone responsible for inducing the differentiation of thymocytes. A synthetic peptide corresponding to positions 29-41 of bovine thymopoietin II, which can reproduce this function of the parent molecule in vitro, also caused neostigmine-responsive neuromuscular block in mice similar to that which thymopoietin itself produces, and which resembles the neuromuscular block of myasthenia gravis. This 13 aminoacid sequence must therefore contain the key residues in the thymopoietin molecule responsible for both T-cell differentiation and neuromuscular effects. These data provide further support for the view that myasthenia gravis is a consequence of thymic disease associated with systemic release of thymopoietin, with ensuing neuromuscular block. This evidence supports the empirically proven treatment of myasthenia gravis by early total thymectomy.