P036

• Published in: Human immunology Vol. 75; p. 73
• Main Authors: Gandhi, Manish J, DeGoey, Steven, Henderson, Nicole, Voit, Laurie, Kreuter, Justin
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: Allergy and Immunology
• ISSN: 0198-8859
• DOI: 10.1016/j.humimm.2014.08.098

Detection of donor-specific anti-HLA antibodies (DSA) by solid phase assay (SpA) helps donor selection by predicting the actual crossmatch (xM), a process referred as a virtual crossmatch (VxM). At our center we find good correlation ( R2 = 0.85) between flow xM (FxM) and VxM using single antigen bead (SAB) assay to identify DSA. The SAB assay is considered a sensitive SpA; however, a concern is that clinically insignificant anti-HLA antibodies (HLA-Ab) may be detected and preclude the recipient from receiving a transplant. The complement fixing (C1q) SAB assay has been proposed as a way to minimize the detection of clinically insignificant HLA-Ab. We present a summary of our evaluation of this assay. Materials and Methods 20 positive sera, previously used for serological typing, were tested with SAB, at 1:8 dilution with SAB and by C1q SAB method as per the manufacturer’s protocol. Serological HLA-Ab specificities were compared with those that were obtained by SAB and C1q SAB. For the SpA, specificities >5000 MFI were considered as positive. Specificities were grouped into two categories: 5000–10,000 MFI and >10,000 MFI as in our center >5000 MFI correlates with a positive FxM and >10,000 MFI correlates with cytotoxicity xM. Results In total there were 53 HLA-Ab specificities as defined by serology, 328 as defined by SAB, and 123 as defined by C1q. SAB identified all 53 specificities defined by serology; 49 with MFI >10,000. Of the 4 with MFI 10,000 on 1:8 dilution and other 2 were not detected by C1q assay. In addition, C1q assay did not detect 3 specificities identified by serology (all with MFI >10,000 by SAB). C1q assay identified 123/179 (69%) of the specificities with MFI >10,000 and 0/151 specificities with MFI: 5000–10,000 as detected by SAB (table). Conclusions For Class I HLA-Ab, C1q assay only detects high titer/avidity antibodies as defined by SAB. As DSA with SAB MFI: 5000–10,000 can result in a positive FxM, additional investigation is warranted to determine the clinical significance of these HLA-Ab. Serology positive N % SAB Total positive 53 100 MFI: >10,000 49 92 MFI: 5000–10,000 4 8 Total negative 0 0 C1q SAB Total positive 47 89 MFI: >10,000 47 89 MFI: 5000–10,000 0 0 Total negative 5 11 M.J. Gandhi: Consultant; Company/Organization; Thermo Fisher-One Lambda.