Heart transplantation across antibodies against human leukocyte antigen and ABO-post-transplant follow-up of donor reactive antibodies.

Background: We have successfully performed heart transplantation despite the most unfavourable risk factors for graft and patient survival: the presence of a high level of antibodies (Abs) against the donor's human leukocyte antigens (HLA) class I/II and blood group A1 antigens. The present study concerns post-transplant follow-up and characterization of donor reactive antibodies (DRA).

Methods: Pre-transplant treatment consisted of mycophenolate mofetil (MMF), prednisolone, tacrolimus, intravenous immunoglobulin (IVIG), rituximab, protein-A immunoadsorption (PAIA) and per-operative plasma exchange. A standard triple-drug immunosuppressive protocol was used post-operatively. Abs were analyzed by the complement dependent cytotoxicity (CDC) test against donor and panel B/T cells and by flow cytometry (FlowPRA tests detecting isolated HLA class I/II antigens). Abs against the donor's erythrocytes were analyzed using a standard direct agglutination test for immunoglobulin M (IgM) Abs and a Bio-Rad AHG gel card test detecting IgG Abs and C3d.

Results: Pre-transplant treatment reduced Ab titers against the donor's lymphocytes from 128 to 16 and against the donor's blood group A1 antigen from 256 to 0. The patient was emergently transplanted with a heart from a blood group incompatible donor (A1 secretor to O). No hyperacute rejection was seen. DRA were present against all mismatched HLA class I and class II antigens at the time of transplantation; two of these DRA Abs disappeared within the first year post-transplant (anti-B62 and anti-DR4), one showed weakened reactivity (anti-A24) and one is still strongly reactive (anti-DQ3). The donor-specific CDC cross-match is still positive (titers 2 to 8). The level of panel reactive antibodies (PRA) remained unchanged from 6 months on post-transplant. Rising anti-A1 blood group Abs preceded the second rejection and were adsorbed by two blood group specific immunoadsorptions (Glycosorb)-ABO) and remained at a low level. IgM anti-A1 blood group Abs disappeared at 1 yr post-transplant and IgG Abs are still reactive with blood group A1 erythrocytes but at low titers (1 to 2).

Conclusions: The patient is clinically well 2 years after heart transplantation despite the constant persistence of donor reactive IgG Abs against blood group A1 and HLA-DQ antigens. The reactivity of DRA against other mismatched HLA antigens disappeared or weakened during the follow-up period.