Background: Rituximab is commonly prescribed in ABO- or HLA-incompatible kidney transplantation. When used before transplant it interferes with B lymphocyte complement-dependent crossmatch (CDC CM) or FACS crossmatch (FACS CM) results thus rendering their interpretation impossible. This effect has been described up to 9 months following rituximab infusion.

We describe here a new method to abolish rituximab interference in both CDC CM and FACS CM.

Methods: We used an anti-rituximab mouse monoclonal antibody (10C5 clone, ABNOVA®) directed against the F(ab)2 fragment of rituximab. Normally this antibody is employed to dose rituximab by ELISA technique.

We tested different antibody concentrations in different settings (rituximab infusions 0 days to 270 days before CM; patients with and without class 1 and 2 HLA antibodies) and evaluated whether the interference of rituximab was abolished in FACS CM and CDC CM.

Results: A concentration of 0.17[micro]g/[micro]l of the 10C5 clone abolished completely false positive results in both CDC and FACS CM. 1[micro]l of 10C5 was thus added to 5[micro]l of serum for 15 minutes at room temperature, the CM was then performed. While these concentrations dilute the serum they did not nullify expected positive results. CDC and FACS CM stayed positive when donor specific HLA antibodies had a Luminex mean fluorescence intensity respectively >8000 and >4000.

Conclusion: We describe an easy, efficient and relatively inexpensive method to eliminate rituximab interference on CDC and FACS CM results.

CITATION INFORMATION: Malvezzi P., Senoussi O., Jouve T., De Palma C., Rostaing L., Bardy B., Masson D. Rituximab Interference in B-Cell Crossmatch: A Problem Solved Am J Transplant. 2017;17 (suppl 3).

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