The Bombay blood group kidney transplant has long been considered one of the most formidable immunologic challenges in transplant medicine. For decades, severe blood group mismatches were viewed as an absolute contraindication to renal transplantation.
Today, I am proud to share that a landmark study from my team at MIOT Hospitals, Chennai has been published in the American Journal of Transplantation. The paper, first-authored by our colleague Dr. Thiagarajan Yashwanth Raj, with me serving as the senior and lead author, describes what is, to our knowledge, the world’s first Bombay blood group kidney transplant in a recipient with the classical digenic Bombay phenotype.
The Challenge: Bombay Phenotype and Solid Organ Transplantation
The Bombay blood group is an exceptionally rare blood phenotype—occurring in approximately 1 in 10,000 individuals in India and 1 in 250,000 globally. Resulting from loss-of-function mutations in the FUT1 gene and concurrent FUT2 deficiency, individuals with this phenotype lack the H antigen on their red blood cells and secretions.
Because the H antigen acts as the underlying precursor for A and B blood group antigens, Bombay phenotype recipients generate strong, pre-formed anti-H antibodies alongside anti-A and anti-B isoagglutinins. Standard organ donors express the H antigen on their vascular endothelium. Consequently, placing an H-expressing kidney into a Bombay phenotype recipient historically presented a prohibitive risk of hyperacute graft rejection.
Without a rare, matched Bombay phenotype donor, transplantation was previously considered impossible. Patients with end-stage kidney disease and the Bombay phenotype were effectively left without a living-donor option—a particularly severe limitation in India, where the Bombay phenotype is more prevalent than in most other populations. This is what makes the Bombay blood group kidney transplant described here a genuine breakthrough.
Case Presentation and Desensitization Strategy
A 30-year-old male with end-stage kidney disease secondary to IgA nephropathy was evaluated for a living-donor kidney transplant, with his mother (blood group B) as the donor. Genetic analysis confirmed a homozygous missense variant in FUT1 (p.Leu242Arg) and a FUT2 homozygous deletion. High-titer anti-H antibodies (IgG titer 1:64) and anti-B antibodies were identified.
To clear the immunological barrier, the team implemented a targeted pre-transplant desensitization protocol featuring:
- Rituximab to inhibit B-cell antibody production
- Therapeutic Plasma Exchange (TPE) paired with Intravenous Immunoglobulin (IVIg) to lower circulating isoagglutinins
- Maintenance immunosuppression utilizing Tacrolimus, Mycophenolate Mofetil, and Steroids
By the day of surgery, the recipient’s IgG anti-H titer was safely lowered to 1:16. The transplant was performed successfully under Basiliximab induction without perioperative complications.
Clinical Outcomes and Future Implications
At 14 months post-transplant, the recipient demonstrated stable renal function with a serum creatinine of 1.6 mg/dL and persistently low anti-H titers (1:8).
This sustained graft function suggests that immunological accommodation—a known phenomenon in standard ABO-incompatible transplantation—can also occur across the ABO-H incompatibility barrier. In other words, the recipient’s immune system appears to have adapted to the presence of the H antigen without rejecting the graft, opening a pathway that was previously thought to be immunologically closed.
Key Clinical Insights
- Controllable Isoagglutinin Thresholds: Pre-transplant desensitization can reduce high-titer anti-H antibodies to clinically safe thresholds (1:16 or lower).
- Expanding Donor Pools: The Bombay blood group phenotype should no longer be viewed as an absolute contraindication to living donor kidney transplantation.
- Proof-of-Concept: Tailored antibody removal opens new pathways for patients with rare blood phenotypes facing organ failure.
Dr. Rajan Ravichandran’s Broader Work in ABO-Incompatible Transplantation
This achievement did not emerge in isolation. Dr. Rajan Ravichandran’s team at MIOT Hospitals has one of India’s most extensive clinical experiences in ABO-incompatible kidney transplantation, documented across multiple peer-reviewed publications—including long-term follow-up studies, a single-centre case series, a review of ABO-incompatible transplantation from an Indian perspective, and experience with Bortezomib-based desensitization protocols. The Bombay blood group kidney transplant represents the logical extension of that two-decade body of work into the most extreme form of blood group incompatibility encountered in clinical practice.
Dr. Rajan Ravichandran is the senior and lead author of this study, Director of Nephrology at MIOT Hospitals, and Chairman of Sapiens Health Foundation.
Citation: Raj TY, et al. Kidney Transplantation Across ABO-H Incompatibility in a recipient with Bombay Blood Group: A Novel Report. American Journal of Transplantation. 2026;26(3):646-649. doi: 10.1016/j.ajt.2025.11.002. PMID: 41238022.
