Production and characterisation of monoclonal antibodies against a very small hapten, 3-methylindole

Monoclonal antibodies were produced against a very small (131.2 Da) hapten, 3-methylindole. Nine derivatives of 3- methylindole were synthesised with spacers ending in a carboxyl group, and coupled to immunogenic carriers and europium chelate labels. Almost all the antigens elicited an antihapten re sponse, but the majority of the mAbs produced strongly recognised the space r group and did not bind free 3-methylindole. However, specific antibodies were obtained with five immunogens. Specificity could be directed against t he pyrrole ring by locating the bridging group to the aromatic moiety of th e indole ring system. Any modification in the position 3 of the indole ring strongly hindered mAb binding to the compound, and the cross-reactivity of physiologically important compounds, such as tryptophan and tryptamine, wa s negligible for all of the mAbs. The developed hapten structures successfu lly focused antibody recognition to the important sub-determinants in the i ndole ring system. Similar constructs could also be useful in the developme nt of antibodies against other indolic compounds. (C) 2000 Elsevier Science B.V. All rights reserved.