Species-specificity of human anti-beef, pork insulin

Previous studies have revealed the presence of insulin-binding antibodies in the serums of in-sulin-treated human subjects. Antigen-antibody complexes in this system do not precipitate out of solution but are readily identified by paper chro-mato-electrophoresis employing insulin-I13 ' ( 1). Kinetic studies of the reaction between crystalline beef insulin and antiserum have indicated that in-sulin is probably univalent and that there are at least two distinct orders of antibody-combining sites (2-4). Since insulins from five different mammalian species have been found to differ in amino acid sequence only in positions 8 to 10 of the A (glycyl) chain (5), it appeared of interest to study the reactivity and cross reactivity of these various insulins in the same antiserum. Studies with human insulin, several different preparations of beef insulin, including beef des-amido insulin, and the A and B chains of insulin are also reported. MATERIALS AND METHODS The following species-specific insulins and insulin fractions 1 were labeled with I...: beef insulin (Lilly, Lot No. 535664), pork insulin (Lilly, Lot No. 499667), horse insulin, sheep insulin, beef insulin (Boots 2), desamido insulin derived from the Boots beef insulin by countercurrent fractionation by Dr. Lyman Craig, A chain and B chain of beef insulin. All the aforementioned in-sulins were crystalline preparations. A crude prepara-1 We are greatly indebted to Doctors 0. H. Behrens and C. W. Pettinga for supplies of the Lilly beef and pork insulins, to Dr. Hans Neurath for the horse insulin, to Dr. L. Craig for Boots beef insulin, desamido insulin, sheep insulin, and A and B chains, and to Doctors F. Tietze and J. Field for human insulin. The Lilly beef and pork insulins assayed at 27 to 29 units per mg. and the horse insulin at 25 units per mg. in the Lilly labora-tories. The Boots beef insulin assayed at 21 to 23 units per mg. in the Boots laboratories but this insulin is said to be comparable in purity to that of the Lilly prepara-tions (6). The desamido insulin showed the same hor-monal potency as the parent preparation (6). 2 Standardized sample of insulin from the Commissio