Decrease of antibodies to insulin, proinsulin and contaminating hormones after changing treatment from conventional beef to purified pork insulin.

The sera of 30 patients who had been treated with conventional beef insulin were tested for binding of insulin and other pancreatic hormones. All showed antibody binding of insulin, 29 binding of proinsulin, 29 binding of pancreatic polypeptide, two binding of glucagon but none of the sera bound vasoactive intestinal peptide or somatostatin. After changing therapy to highly purified pork insulin the binding capacity of sera for insulin and the other hormones was monitored for up to 35 months and a steady fall was found in nearly all cases. In eight of the patients conventional beef insulin treatment was resumed: in one month binding of insulin and of the other hormones increased back to the initial levels. In eighteen subjects who had only received highly purified pork insulin low levels of insulin binding were found with no binding of proinsulin or other hormones. The amounts of proinsulin and contaminating hormones in highly purified pork insulin are so low that they are not immunogenic; conventional beef insulin not only contains immunogenic amounts of proinsulin and the contaminating hormones pancreatic polypeptide and glucagon but also is more immunogenic than purified pork insulin.