Blood type change identifies late dominance reversal of chimerism after double umbilical cord blood transplantation with review of the literature.

BACKGROUND

A 30-year-old man underwent double umbilical cord blood transplantation (UCBT) for acute myeloid leukemia (AML) with reduced intensity conditioning. The cords had identical HLA types and were each a 5/6 match to the patient. Following transplantation, cord 2 initially dominated all tested cell populations. At day +306, we observed an unusual reversal of dominance chimerism pattern in which cord 1 instead dominated all tested populations.

STUDY DESIGN & METHODS: Polymerase chain reaction (PCR)-based short tandem repeat (STR) assays were performed on the peripheral blood and bone marrow samples. The white blood cell (WBC) populations from the peripheral blood were manipulated for testing to create subpopulations enriched for CD3, CD33, and CD56.

RESULTS

Chimerism studies on day +77 showed the following: cord 1: 44%-CD3; 0%-CD33; 16%-CD56; cord 2: 56%-CD3; 100%-CD33; 84%-CD56. Cord 2 initially dominated in all tested cell populations. Chimerism studies performed on post-transplantation day +306 uncovered a reversal of dominance chimerism pattern in which cord 1 now dominated in all cell populations (cord 1: 82%-CD3; >95%-CD33; 67%-CD56; cord 2: 18%-CD3; <5%-CD33; 33%-CD56). Between days +127 and  +244, the patient's blood type shifted from B Rh-positive to A Rh-negative.

CONCLUSION

The change in the patient's blood type identified a late reversal of dominance chimerism pattern. This is a rare occurrence, previously cited only once, which is inconsistent with published data that early high CD3 counts and unseparated bone marrow chimerism predominance at day +100 predict long-term cord dominance in double UCBT in the vast majority of cases.