A flow cytometric method for the detection of the development of antibody to Orthoclone OKT3

Orthoclone OKT3 is a monoclonal antibody used in the treatment of transplant rejection. The development of anti-OKT3 antibodies after therapy with this drug is a side effect which must be monitored. The current ELISA test to detect these antibodies is difficult to standardize between laboratories and does not lend itself to frequent monitoring of small numbers of samples. This prompted us to develop a new method employing flow cytometry to detect the development of anti-murine antibodies. Comparing samples tested by both techniques, we found the flow cytometric method to be more sensitive and as the ELISA methodology. This technique is adaptable to numerous serologic assays and could greatly expand the use of flow cytometry in the clinical laboratory.