Somatomedin production and response to mitogen by lymphocytes in children with growth hormone deficiency

Studies on the lymphocyte proliferative activity of the sera from growth hormone (GH) deficient patients have resulted in contradictory observations. The ability of lymphocytes to synthesize somatomedin-C (Sm-C) and thus account for a normal proliferative activity (previously observed by us) of the GH-deficient sera was studied, by measuring Sm-C concentration in the culture medium using a standard radioimmunoassay for Sm-C. The response of lymphocytes to the mitogen phytohemagglutinin (PHA), as determined by the incorporation of 3H thymidine into DNA, was also studied. The Sm-C concentrations in the cultures reflected the Sm-C concentrations of the respective serum added and did not alter with significant increases in the cell number induced by PHA. The lymphocytes from GH-deficient children and normal children were indistinguishable in their ability to respond to PHA. We conclude that lymphocyte proliferation in short-term culture, was not associated with an increase in Sm-C and that in the lymphocyte proliferation assay the sera and the lymphocytes from GH-deficient children respond similarly to the sera and lymphocytes from normal children.