Antibodies with high affinity for spiroperidol--II. Cross reactivity with iodobenzamide and domperidone.
Three radioligands, 3H-spiroperidol (3H-SPD), 3H-domperidone (3H-DOMP) and 125I-iodobenzamide (125I-IBZM), were used to investigate the antibody response to two haptens, aminospiroperidol (NH2SPD) and N-aminophenethylspiroperidol (NAPS). Although structurally different, these three radioligands each bind with high affinity to the D2 dopamine receptor. Antibodies with high affinity for 3H-SPD were elicited in rabbits following immunization with the hapten NH2SPD covalently linked to keyhole limpet hemocyanin (KLH). In addition, antibodies in the rabbit anti-NH2SPD antisera bound 125I-IBZM or 3H-DOMP. Rabbit anti-NH2SPD antibodies that bound 125I-IBZM or 3H-DOMP were found to have higher affinity for IBZM or DOMP, respectively, than for SPD. The binding properties of the anti-NH2SPD antibodies that bound 3H-SPD, 125I-IBZM and 3H-DOMP were characterized using a panel of competitive inhibitors and each radioligand appeared to bind to a distinct subpopulation of anti-NH2SPD antibodies. BALB/c mice were immunized with NH2SPD-KLH or NAPS-KLH. A population of antibodies that bound 3H-SPD and a population of antibodies that bound 3H-DOMP were detected. The population of antibodies that bound 3H-DOMP was found to be heteroclitic for DOMP, since DOMP was a more effective competitive inhibitor than SPD. Binding sites for 125I-IBZM were not detected in either the anti-NH2SPD or the anti-NAPS BALB/c antisera. However, two anti-NAPS monoclonal antibodies, N6-24 and N6-29, that bind 3H-SPD with high affinity (Kd = 10(-9) M), were also found to bind IBZM (Ki = 2 x 10(-7) M) and DOMP (Ki = 2 x 10(-6) M). Although anti-NH2SPD and anti-NAPS antibodies were identified that appeared to bind 3H-SPD, 3H-DOMP or 125I-IBZM with high affinity, none of the populations of polyclonal antibodies or monoclonal antibodies bound all three ligands with high affinity.
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104.
R R
RR
Luedtke
M
M
Bush
R H
RH
Mach
R E
RE
Ehrenkaufer
H F
HF
Kung
P B
PB
Molinoff
D000818:Animals; D000910:Antibodies, Heterophile / Q000276:immunology; D000915:Antibody Affinity; D000918:Antibody Specificity; D001549:Benzamides / Q000276:immunology*; D001667:Binding, Competitive; D003429:Cross Reactions; D004294:Domperidone / Q000276:immunology*; D006241:Haptens; D006825:Hybridomas / Q000276:immunology; D051379:Mice; D011759:Pyrrolidines / Q000276:immunology*; D011817:Rabbits; D013134:Spiperone / Q000276:immunology*
D000910:Antibodies, Heterophile; D001549:Benzamides; D006241:Haptens; D011759:Pyrrolidines; D013134:Spiperone; D004294:Domperidone; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide