ABO, alemtuzumab and allogeneic transplantation

To the Editor

“…Donor RBCs are usually detected within 3-6 weeks after HSCT but can be significantly delayed, especially with group A/group O major-incompatible HSCT, high-titer ABO antibodies in the recipient, and nonmyeloablative, reduced-intensity conditioning (RIC) chemotherapy. [2][3][4] At some point after gaining evidence of stable engraftment and transfusion independence, the patient's ABO blood group is officially changed to that of the HSCT donor. At our institution, a patient may be considered for an ABO blood group change 1 year after ABOi HSCT, provided that (1) the patient has no clinical or laboratory evidence of disease relapse, (2) the patient has not received any transfusions for at least 3 months, (3) there is no evidence of mixed-field agglutination in the forward typing, (4) a direct antiglobulin test is negative, and (5) an isoagglutinin crossmatch of recipient plasma against the donor ABO-group RBCs is negative (tube method; 15 minutes at room temperature incubation, and indirect antiglobulin test [15 minutes at 37°C incubation, anti-IgG]).…”

“…SCID patients who undergo conditioning chemotherapy will show donor RBC engraftment at rates similar to other allogeneic ABOi transplants. [2][3][4] Laura L.W. Cooling ) not done at the time of testing.…”

“…2 Furthermore, patients with high-titer ABO antibodies may undergo a prophylactic, pre-transplant plasma exchange to further reduce the risk of acute hemolysis, delayed RBC engraftment, and pure RBC aplasia. [2][3][4] ABO minor-incompatible HSCTs, in which donor plasma is ABOi with the recipient, have less risk for hemolysis at the time of infusion but can result in transient hemolysis approximately 10-21 days post-transplant, especially in patients undergoing nonmyeloablative HSCT and/or patients who have not received methotrexate for graft-versus-host-disease (GVHD) prophylaxis. [1][2][3][4] In these patients, viable donor B-lymphocytes in the graft may expand and produce ABO antibodies capable of hemolyzing patient RBCs.…”