HETEROLOGOUS HUMORAL IMMUNE-RESPONSE IN PATIENTS TREATED WITH HUMAN GROWTH-HORMONE FROM DIFFERENT SOURCES

The existence of homologous anti-human growth hormone (anti-hGH) and h eterologous anti-bovine growth hormone (anti-bGH) humoral immune respo nses in hypopituitary patients under hGH therapy has been reported pre viously. In order to study the influence of the hormone source, both r esponses were compared by radiobinding assays performed with [I-125]bG H or [I-125]bGH as tracers. Fifty-seven hypopituitary patients treated with extractive hGH, recombinant methionyl hGH or authentic recombina nt hGH were studied. A very low incidence of heterologous antibodies w as found in patients under recombinant hGH therapy, contrary to the hi gh incidence observed in patients treated with extractive hGH preparat ions. In addition, immunochemical studies performed with a synthetic p eptide (hGH 44-128) indicated that this peptide exhibited, in the anti -bGH/[I-125]bGH radioimmunoassay system, higher reactivity than the na tive hGH, suggesting that such a fragment resembled an altered conform ation of the hormone. The high heterologous response elicited only by the extractive hGH along with the behaviour of the hGH 44-128 fragment supports the fact that the extraction and purification procedures in extractive preparations may alter slightly the structure of the hGH mo lecule and trigger a heterologous immune response.