Problems connected with the production of highly specific antisera against prostaglandin E2 (PGE2) and prostaglandin A2 (PGA2) for radioimmunoassay

To obtain sensitive and specific antisera against PGE2 and PGA2 these substances were coupled to thyroglobulin (Tg). Coupling reactions were either performed by using a hydroxysuccinimideester as intermediate step leading to a complex carrying 170 mol PGE2 per mol Tg ('PGE2-OSU-Tg') and 240 mol PGA2 per mol Tg ('PGA2-OSU-Tg') or alternatively by using N,N'-carbonyl-diimidazole resulting in 'PGE2-CDI-Tg' (400 mol PGE2 per mol Tg) and 'PGA2-CDI-Tg' (600 mol PGA2 per mol Tg). Two tracer systems (3H-prostaglandin, 125I-histamine-prostaglandin) were used for analysis of antibody activity. Both PGE2- and PGA2-CDI-Tg complexes were poor immunogens in rabbits. The PGE2- and PGA2-OSU-Tg conjugates were injected both in rabbits and in guinea pigs. These two compounds resulted in very high antibody titers in both animal species. However, in guinea pigs markedly higher antibody sensitivity and antibody specificity were observed than in rabbits. Our results indicate that the guinea pig may be the animal of choice for immunization against prostaglandins. Antibody specificity of guinea pig antisera may be perhaps high enough to measure the concentration of PGE2 and PGA2 in the presence of other prostaglandins or prostaglandin metabolites. (orig.)