Donor HLA-specific Abs: to BMT or not to BMT?

Area of Science:

• Immunology
• Hematology
• Transplantation Medicine

Background:

• Engraftment failure in bone marrow transplantation (BMT) is often caused by antibodies to donor-specific human leukocyte antigens (DSA).
• Sensitized BMT candidates with limited donor options face significant challenges due to DSA.
• Current desensitization protocols may not be suitable for all BMT candidates.

Purpose of the Study:

• To evaluate the efficacy of a modified desensitization regimen in patients with donor-specific HLA antibodies undergoing BMT.
• To assess the impact of desensitization on DSA levels and subsequent engraftment in highly sensitized BMT candidates.
• To identify factors influencing the response to desensitization and post-transplant outcomes.

Main Methods:

• A cohort of 14 highly sensitized patients with limited donor options received desensitization therapy.
• The regimen included plasmapheresis and low-dose intravenous immunoglobulin (IVIg), modified for pre-BMT conditioning.
• Donor-specific HLA antibody (DSA) levels were measured using solid-phase immunoassays and cell-based crossmatch tests, with monitoring for rebound.

Main Results:

• A mean DSA reduction of 64.4% was achieved post-desensitization and 85.5% post-transplantation.
• Eleven patients achieved DSA levels considered negative post-BMT; three had low residual DSA.
• All 14 patients achieved donor engraftment by day +60, though seven experienced disease relapse and four had mild GVHD.

Conclusions:

• Modified desensitization protocols can facilitate successful engraftment in sensitized BMT candidates with limited donor options.
• Careful assessment and monitoring of DSA levels are critical for managing desensitization and improving BMT outcomes.
• Factors such as initial DSA strength, specificity, and rebound influence treatment response.