Comparison Of Different Immunoadsorption Techniques And Plasma Exchange

Comparison Of Different Immunoadsorption Techniques And Plasma Exchange

In the management of ABO-incompatible (ABOi) kidney transplantation, different antibody-removal techniques—classical plasma exchange (PEX), double-filtration plasmapheresis (DFPP), and immunoadsorption (IA)—are used to reduce anti-A/B titers to safe levels (typically <1:8). While all serve the same clinical goal, they differ significantly in selectivity, efficiency, and procedural risks.

1. Classical Plasma Exchange (PEX/PP)

PEX is the most established and widely available method, particularly in the United States and Australia.

• • Mechanism:
    The patient’s plasma is separated (via centrifugation or large-pore filtration) and completely replaced with a substitute such as albumin, colloid solutions, or fresh frozen plasma (FFP).

• Advantages:
  Less expensive and more rapidly available than specialized adsorption columns.
  Effective at removing non-ABO factors such as anti-HLA antibodies and complement components.

• Disadvantages:
  Non-selective removal leads to loss of essential plasma components, including coagulation factors, hormones, albumin, and protective antibacterial/antiviral immunoglobulins.
  Centrifugation-based PEX can also cause substantial platelet loss (up to 50%).

2. Double-Filtration Plasmapheresis (DFPP)

Commonly used in Japan and Europe, DFPP offers a more targeted approach than classical PEX.

• Mechanism:
  A secondary filter selectively removes the gamma-globulin (immunoglobulin) fraction before the remaining plasma is returned to the patient.
• Efficiency:
  Highly efficient; the amount of immunoglobulin removed in a single session is equivalent to the concentration found in 5 liters of plasma.

3. Immunoadsorption (IA)

IA represents the most selective category of antibody removal and is the cornerstone of many European “modern era” protocols.

• Antigen-Specific IA:
  Uses columns (such as the Glycosorb device) coated with synthetic blood group A or B antigens.
  Selectively binds anti-A or anti-B antibodies while preserving essential plasma proteins and protective antibodies.
• Non-Antigen-Specific IA:
  Uses protein A or polyclonal sheep anti-human IgG antibodies to clear a broader range of immunoglobulins.
• Clinical Benefits:
  Highly efficient, prevents loss of essential plasma components, and reduces complement components, which may help prevent Antibody-Mediated Rejection (ABMR).

4. Comparison of Clinical Risks and Outcomes

• Bleeding Risk:
  ABOi recipients face a doubled risk of bleeding compared to compatible recipients, regardless of whether PEX or IA is used.
  In IA, the number of preoperative sessions is the only independent predictor of bleeding; each session increases the odds of requiring a transfusion by 1.9.
  IA using filtration techniques causes roughly a 28% drop in platelet count.
• Infection Risk:
  Because PEX removes protective immunoglobulins, it has been hypothesized to carry a higher infection risk.
  However, de Weerd’s meta-analysis found no significant difference in mortality or infectious complications between IA and PEX subgroups.

Graft Survival:
One meta-analysis (Lo et al.) suggested graft survival was worse after PEX compared to IA.
In contrast, the de Weerd meta-analysis found similar patterns of safety and efficacy for both techniques.