[Binding of the monoclonal antibody BW 250/183 to human granulocytes]. / Bindung des monoklonalen Antikörpers BW 250/183 an menschliche Granulozyten.

Lately, the specific binding of appropriate monoclonal antibodies to human granulocytes has been used for the scintigraphic detection of inflammatory foci. Using the antibody BW 250/183 we studied the underlying binding kinetics. As an important requirement for a specific cell binding it has been shown that the labelling procedure does not change the immunoreactivity of the antibody. An affinity constant of 2 x 10(9) l/mol has been calculated from binding studies. Usually, 0.25-1.0 mg of the 99mTc-labelled antibody are applied per patient. In the present study an equilibrium in blood appeared quickly after intravenous application; at steady state about one fourth of the activity was cell-bound. The rest of the activity circulated in the plasma in the form of labelled IgG and was able to react directly with those granulocytes which were already accumulated in the inflamed area. Even a drastic reduction of the applied protein mass did not change this equilibrium. The law of mass action seems not to be directly applicable to this problem. Interferences with components of the plasma can be excluded as explanation for this behaviour. After application of in-vitro labelled granulocytes from which unbound antibodies were removed completely by washing, an identical steady state was observed within 10 min after injection; however, in this situation the intravasal residence time of activity increased distinctly.

Folding and association of triose phosphate isomerase from rabbit muscle.

The enzymatic activity and quaternary structure of rabbit muscle triose phosphate isomerase remains unchanged in the concentration range from 2 micrograms/ml to 2 ng/ml. In this concentration range the enzyme can be reactivated after dissociation and denaturation in 6.5 M guanidine hydrochloride. Removal of the denaturant by dilution and separation of inactive wrong aggregates (5-20%) lead back to active dimers, indistinguishable from the native enzymes as far as enzymatic and physicochemical properties are concerned. Based on the long term stability of the enzyme, the reactivation kinetics were analyzed at low concentrations and 0 degrees C, conditions where the association of inactive monomers to active dimers is predominant in the process of reactivation. The concentration dependence of the rate of reactivation and the kinetic profiles could be described by a consecutive first-order folding and second-order association reaction scheme with the rate constants kuni = 1.9 X 10(-2)s-1 and kbi = 3 X 10(5) M x s-1. This implies that the folded monomers of triose phosphate isomerase, which are intermediate states during reconstitution, cannot possess appreciable enzymatic activity.