Facilitation of the growth promoting effect of growth hormone (GH) by an antibody to methionyl-GH.

Despite the development of antibodies to methionyl growth hormone in a child with hypopituitarism, the patient grew at a rapid rate on low doses of somatotropin. Serum immunoglobulins from this patient stimulated the growth of Nb2 lymphoma cells in vitro in samples obtained within 48 hours after the last dose of growth hormone, while samples obtained several weeks after an injection of methionyl growth hormone did not. Immunoglobulins from normal subjects or from hyposomatotropic patients being treated with methionyl growth hormone who had not developed antibodies did not stimulate Nb2 lymphoma cell growth. We suggest that the antibodies to methionyl growth hormone in this child served as a reservoir for exogenous growth hormone or facilitated the interaction of growth hormone with the prolactin receptor on the Nb2 lymphoma cell.