A unique high-titer antiserum to gastrin

Among twenty rabbits immunized with hexadecapeptide gastrin coupled to bovine serum albumin, one (No. 4562) produced, after four immunizations, antisera with a titer of 108. The titer remained above 107 for 8 months without boosting. Upon storage the titer declined to 4 ± 106 after a year irrespective of storage conditions. The titer has remained stable at this level for 5 years, After the third immunization the avidity has remained high, Ko eff. varying from 9 to 5 ± 1012 l/mol. The antiserum binds the bioactive C-terminus of gastrin. Using tyr-12 monoiodinated gastrin as tracer, ID50 gastrin-17 (ns); ID50 cholecysto-kinin-33 is 0.026. Sulphated gastrins are bound less well than non-sulphated forms, ID50 gastrin-17 (ns) : ID50 gastrin-17 (s) being 0.08. For gastrin component I and gastrin-34 ID50 gastrin-17 (ns): ID50 gastrin-34 (ns) or component I is 0.7. The binding homology of the antiserum is high, α (the heterogeneity index) varying between 0.68 and 0.85. Samples of the antiserum have now been distributed to more than 200 laboratories for radioimmunoassay, immunosorption and immunocytochemistry.