Evaluation of the immunoreactive fraction of an anti-tumour monoclonal antibody.
Over a period of approximately 1 year, the immunoreactivity of the anti-ovary carcinoma MAb MOv18 was evaluated after radiolabelling with 125I on two different ovarian carcinoma cell lines, OvCa432 and IGROV1. A high variability of the immunoreactive values was observed by analysing different preparations of radiolabelled MOv18 (from 12 to 21% on OvCa432 and from 22 to 56% on IGROV1) and by using the same radiolabelled preparation (12% on OvCa432 and 51% on IGROV1). Since the variability could be due to the target cells, we set up an alternative binding assay using the anti-idiotypic MAb anti-Id18.1 directed against a private idiotype closely associated with the MOv18 paratope. Three different experiments carried out with the anti-idiotypic MAb gave reproducible results with an immunoreactive range from 71 to 83%. A direct comparison between the reactivity of the same 125I-MOv18 preparation on anti-Id18.1 and on IGROV1 confirmed the higher value of the immunoreactive fraction estimated on the more homogeneous anti-idiotypic reagent (71%), rather than on the tumour cells (56%). These data suggest that anti-idiotypic MAbs could represent suitable reagents for the evaluation of the immunoreactivity of an antibody preparation after radiolabelling and before in vivo administration.
Mantovani
L
L
Division of Experimental Oncology E. Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy.
Ménard
S
S
Mezzanzanica
D
D
Miotti
S
S
Pupa
S M
SM
Colnaghi
M I
MI
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal / Q000276:immunology*; D005069:Evaluation Studies as Topic; D006801:Humans; D007457:Iodine Radioisotopes; D009369:Neoplasms / Q000276:immunology*; D014407:Tumor Cells, Cultured
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes