Clinical investigations utilizing murine monoclonal antibodies require
techniques for the detection of the human anti-mouse antibody (HAMA)
response in patient serum. We report here a flow cytometric assay for
the quantitation of HAMA. Commercially available beads conjugated with
goat anti-mouse antibody provide a solid phase matrix for a triple br
idge immunoassay. The measurement of fluorescein labeled antibodies by
flow cytometry allows accurate quantitation of the HAMA. The assay wi
ll detect antibody levels of approximately 1.0 ng/ml. Antibody recover
y in serum samples with known amounts of antibody added was greater th
an 90% at levels greater-than-or-equal-to 10-mu-g/ml. Serum samples ob
tained from 41 patients prior to and after single or multidose infusio
ns of KS1/4-Desacetylvinblastine were analyzed. These results were com
pared with HAMA titers previously determined by ELISA. With few except
ions, patients with low titers as determined by ELISA demonstrated low
HAMA potencies by flow cytometry and those with highest titers the hi
ghest potencies. Patients with no detectable HAMA by ELISA were also n
egative by flow analysis. The results of our studies demonstrate that
HAMA levels can be accurately and quantitatively determined by flow cy
tometry.