Lights and shadows of anti-HLA antibodies detected by solid-phase assay

Recently, management of patients awaiting solid organ transplantation has taken advantages after the development of more sensitive and accurate solid phase assays which have supported the historic complement dependent cytotoxicity. This approach has allowed the detection of antibodies in patients previously considered negative. The use of the single antigen beads resulted in a more accurate anti-human leukocyte antigen (HLA) antibody characterization. The detection of anti-HLA antibodies specific for C, DQ and DP loci that were not so well characterized has been possible through the implementation of the single antigen assay. The assessment of HLA compatibility has been expanded through the introduction of "epitope matching" concept and the definition of the unacceptable antigens for a more adequate evaluation of donor-recipient compatibility. However, the clinical impact of pre-formed and de novo anti-HLA antibodies detected by solid phase assays is still controversial due to the drawback related to result interpretation. Until today, the unresolved issues concern if all antibodies affect the medium and long term clinical outcome. An open debate on the clinical relevance of anti-HLA antibodies detected by single-antigen beads highlights needing to further investigations. Here, we describe the novel applications and the improvements of the solid-phase assay use.