FALSE POSITIVE REACTION AGAINST 73ID EPLET IN SINGLE ANTIGEN BEAD ASSAY

Area of Science:

• Immunogenetics
• Transplantation Immunology

Background:

• The 73ID eplet is present in HLA-A*02:11, which is not on the One Lambda single antigen bead (OL-SAB) panel.
• Reactivity with HLA-A31 and HLA-A33 has been used as a surrogate for detecting antibodies against HLA-A*02:11.

Purpose of the Study:

• To investigate if the 73ID eplet solely explains false-positive reactions against HLA-A*31:01, -A*33:01, and -A*33:03 beads in the OL-SAB.
• To determine the reliability of HLA-A31 and HLA-A33 reactivity as a surrogate marker for HLA-A*02:11 antibodies.

Main Methods:

• Sera from seven patients with the 73ID profile were tested.
• Assays included untreated and acid-treated OL-SAB, adsorption/elution (A/E) experiments, and flow cytometry crossmatch (FCXM).

Main Results:

• Increased mean fluorescence intensity (MFI) was observed with acid-treated beads.
• Antibody recovery was not achieved in A/E assays.
• FCXM results were negative with all tested cells.

Conclusions:

• The 73ID eplet is accessible only in denatured HLA molecules.
• Reactivity solely against HLA-A31 and HLA-A33 in OL-SAB assays is likely false-positive.
• These reactivities are not reliable surrogate markers for HLA-A*02:11 antibodies.