From the Guidelines
For ABO-incompatible (ABOI) kidney transplantation, a pre-transplant anti-blood group antibody titre of 1:8 or lower is generally considered safe for proceeding with transplantation. This threshold is based on clinical experience showing significantly higher rates of antibody-mediated rejection when transplants proceed with titres above 1:8 1. The desensitization protocol typically aims to reduce titres to this level or below before surgery.
Key Considerations
- The protocol usually includes rituximab (375 mg/m² given 2-4 weeks pre-transplant), plasmapheresis or immunoadsorption sessions (typically 2-6 sessions depending on initial titre levels), and intravenous immunoglobulin (IVIG, often 0.1 g/kg after each plasmapheresis) 1.
- Maintenance immunosuppression typically consists of tacrolimus, mycophenolate mofetil, and steroids, started 1-2 weeks before transplantation.
- Post-transplant monitoring of antibody titres is essential, particularly in the first two weeks, with additional plasmapheresis performed if titres rise above 1:8.
Rationale
- Some centers with extensive experience may accept titres up to 1:16 or 1:32, but this carries higher risk and requires more aggressive immunosuppression 1.
- The presence and quantity of antibodies to HLA antigens can fluctuate with time, and patients may display an anamnestic (memory) immune response leading to accelerated rejection despite a negative pretransplant crossmatch with current or pretransplant sera 1.
Important Factors
- Methods used to test for the presence of alloantibodies should be sensitive and identify clinically relevant IgG antibodies to HLA antigens 1.
- Newer assays, such as enzyme-linked immunosorbent assay (ELISA) and Flow Bead, have been introduced to identify antibodies specific to HLA antigens 1.
From the Research
Safe Titre for ABOI Kidney Transplant
- A decrease in the isoagglutinin titer <1:8 is usually required for ABO-incompatible (ABOi) transplantation 2
- The presence of high predesensitization titers may condition future transplantation 2
- Baseline isoagglutinin titer does not influence the prognosis of ABOi patients after desensitization 2
- A higher number of apheresis sessions was observed in patients with titer >128, but this does not influence the number of days of hospital admission 2
Desensitization Protocols
- Desensitization protocols for ABO-incompatible kidney transplantation often include plasmapheresis, rituximab, and immunosuppressive drugs 3, 4, 5
- A low-dose rituximab regimen for ABOI KTX is acceptable for preventing acute antibody-mediated rejection with a low incidence of delayed adverse events 3
- Antigen-specific immunoadsorption, rituximab, and a conventional triple-drug immunosuppressive protocol can be used without splenectomy 4
- A preconditioning protocol consisting of rituximab infusions, splenectomy, plasmapheresis, and pharmacologic immunosuppression enabled ABO-incompatible renal transplantation in patients with high (> 1:512) anti-A/B antibody titer 5
Outcomes of ABO-Incompatible Kidney Transplantation
- Recent reports document outcomes for ABO-incompatible kidney transplantation similar to the outcomes of standard transplantation 6
- Desensitization of the recipient to remove the antibodies and to prevent their rebound after transplantation is a key strategy for overcoming ABO incompatibility 6
- A tailored desensitization approach can be the most efficient strategy, avoiding excess immunosuppression and related side effects 6