Monoclonal antibodies against protease inhibitors: the case of the bovine pancreatic trypsin inhibitor.
A monoclonal antibody (MoAb) directed against bovine basic pancreatic trypsin inhibitor (BPTI or aprotinin), a small protein made up by 58 aminoacids, has been produced. Mice were immunized with the native form of the protein and gave low antibody response. After somatic hybridization of spleen cells from immunized mice, few clones secreting antibodies against BPTI have been found and just two of them were stable. Both secreted IgM. One (ICI) produces a monoclonal antibody which binds to BPTI with an equilibrium dissociation constant, Kd, of 6.1 x 10(-7) M at pH 7.4. Competition experiments demonstrated that ICI recognizes an epitope close to the reactive site of BPTI. Furthermore, Kd of ICI with an isoinhibitor similar to BPTI (S.I. II) but with few differences at the active site is higher, confirming specificity of binding.
Marini
S
S
Dipartimento di Medicina Sperimentale e Scienze Biochimiche, Università degli Studi, Tor Vergata, Rome, Italy.
Fiorucci
L
L
Fioretti
E
E
Giardina
B
B
Ascoli
F
F
D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology*; D000915:Antibody Affinity; D007611:Aprotinin / Q000276:immunology*; D001665:Binding Sites; D000939:Epitopes / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology
D000911:Antibodies, Monoclonal; D000939:Epitopes; C062659:spleen protease inhibitor II; D007611:Aprotinin