Pre-transplant donor-specific B cell memory for prediction of antibody mediated rejection - a pilot study

G.E. Karahan, C. Wehmeier, J. Krop, Y. de Vaal, J. Langerak-Langerak, D.L. Roelen, N.M. Lardy, F.J. Bemelman, I. ten Berge, M.E.J. Reinders, C. van Kooten, S. Schaub, F.H.J. Claas, S. Heidt

Wednesday 13 march 2019

14:08 - 14:10h at Mauritszaal

Categories: Klinisch, Parallelsessie

Parallel session: Parallelsessie IV - Klinisch I

Background: Pre-transplant immunological risk assessment is currently based on the evaluation of donor-specific HLA antibodies (DSA) present in serum. While being an excellent source for HLA antibodies produced by bone marrow-residing plasma cells, serum analysis does not provide information on the memory B cell compartment. Therefore, we have developed a highly sensitive method to profile memory B cell-derived HLA antibodies and evaluated the clinical relevance of this novel method in a pilot study.

Methods: Peripheral blood mononuclear cells (PBMC) and paired serum samples were obtained from transplant candidates with serum HLA antibodies (n=13) and alloantigen non-exposed individuals (n=10). Culture supernatants from polyclonally activated PBMC were either 10-fold concentrated or IgG was isolated from culture supernatants (eluates) using a protein G affinity purification method. Clinical utility of detecting donor HLA-specific memory B cell-derived antibodies (DSA-M) in eluates were investigated in a separate cohort of 20 patients transplanted across a luminex single antigen bead (SAB)-defined serum DSA with negative complement-dependent cytotoxic crossmatches. All patients had at least two allograft biopsies (indication and/or surveillance) within the first year post-transplant. Serum samples as well as processed culture supernatants were tested using luminex SAB assays.

Results: Utilization of eluates enabled detection of HLA-specific B cell memory in 82% of immunized individuals in comparison 64% in 10-fold concentrated supernatants. No B cell memory was detected in eluates of individuals without history of alloantigen exposure, confirming the specificity of the assay. Using this novel, highly sensitive method, DSA-M was detected in 9 patients (45%) with pre-transplant DSA. Patients with concurrent DSA and DSA-M had a higher incidence of of (sub)clinical antibody-mediated rejection (p=0.032) and a higher extent (g≥1+ptc≥1) of microvascular inflammation (67% versus 9%, p=0.02).

Conclusions: The current highly sensitive and easy to apply method for the detection of HLA-specific memory B cells allows for donor-specific memory B cell analyses in clinical settings. Results of our pilot study suggest that analysis of memory B cell-derived HLA antibodies can serve as a novel tool supplementary to serum HLA antibody analysis in pre-transplant risk assessment.