Different efficacy of various blocking reagents to eliminate interferences by human antimouse antibodies with a two-site immunoassay

• Published in: Clinical biochemistry 1996-04, Vol.29 (2), p.145-148
• Main Author: Reinsberg, Jochen
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Blocking; Antibodies, Heterophile - blood; Blood Chemical Analysis - methods; CA-125; CA-125 Antigen - blood; Evaluation Studies as Topic; False Positive Reactions; human antimouse antibodies; Humans; immunoassay; Immunoassay - methods; Indicators and Reagents; interference; Mice
• ISSN: 0009-9120; 1873-2933
• DOI: 10.1016/0009-9120(95)02044-6

Objective: The efficacy of three reagents to eliminate interferences with the cancer antigen 125 (CA-125) assay Enzymun CA-125 II by human antimouse antibodies (HAMA) formed by patients after injection of the murine anti-CA-125 antibody OC125 is compared. Methods: Apparent CA-125 concentrations of 14 serum samples obtained from 6 patients after multiple injections of 1 mg radiolabeled OC125 F(ab′) 2 fragments were measured with the Enzymun CA-125 II before and after preincubation, either with nonspecific mouse IgG, with the polymerized mouse IgG MAK-33, or with the commercially available HAMA-blocking reagent IIR. Results: In all samples with HAM concentrations ranging from 341 to 46900 μg/L, false-positive CA-125 values were measured with the Enzymun CA-125 II, which could be reduced by preincubation with the HAMA-blocking reagents. However, although after preincubation with 2 g/L IIR for all samples the CA-125 concentrations measured were reduced to values within the normal range, after preincubation with 0.7 g/L of polyclonal mouse IgG for five samples and after preincubation with 0.7 g/L of MAK-33 for all samples also the reduced values were considerably elevated. Larger amounts of mouse IgG or MAK-33 led only to a slight reduction of the remaining false-positive CA-125 values. Conclusion: The present results demonstrate that the polymerized mouse IgG MAK-33 and also the normal murine IgG are not suitable for completely eliminating interferences by HAMAs formed after OC125 treatment. Only the HAMA-blocking reagent IIR seems to be an effective agent to eliminate these interferences. Thus, further studies of this material as a blocking reagent seem to be warranted.