P083 : DETERMINATION OF THE CLINICAL USEFULNESS OF HLA NEUTRALIZATION PROFILES

Abstract

Aim Some earlier studies indicated that monoclonal Abs can be neutralized and inhibition measured with a bioassay design structured to reduce 95–100% of the maximal signal at 100 μ g/ml sHLA if operated in the mid linear range of the response signal. The aim of this investigation was to determine whether the theoretical concepts describing the basic nature of neutralization of HLA antibodies could be applied to more complex serological specimen resulting in clinically useful information. Methods Sera specimens were tested by individually adding different combinations of sHLA molecules as neutralizing agents prior to response measurement. After subtraction of the resulting inhibitory profile from the non-treated reference profile, a neutralization profile was generated, visualizing Ab responses directly related to the applied neutralizer allele. Results As shown, sHLA-A ∗ 02:01 was able to 100% neutralize A2-related responses, leaving other HLA/antibody interactions untouched. In this example, when also subtracting B ∗ 08:01 and B ∗ 49:01, a near complete inhibition of the reference profile was achieved. Minor assay-to-assay background fluctuations of 10% can generally be observed. Significantly, HLA antigens considered directly responsible for the immunizing event generally showed a complete inhibition of the reference profile, whereas partial inhibitions were seen as indicator of HLA antibody species present with different antigen/epitope correlation. Conclusion Creating a neutralizer profile subtracting the inhibitory profile from the reference profile is most helpful for better analytical assessment of signal patterns, delivering a positive view of the blocking event, ultimately allowing better interpretation of antibody populations. As demonstrated, complex reactivity patterns could be reduced to more simplifying outputs. We believe that reductive profiling techniques will greatly assist in obtaining more accurate and meaningful data in the assessment of risk for immunologic rejection.