Acquired Downregulation of Donor‐Specific Antibody Production After ABO ‐Incompatible Kidney Transplantation

The mechanism of long‐term B cell immunity against donor blood group antigens in recipients who undergo ABO ‐incompatible ( ABO i) living‐donor kidney transplantation ( LKT x) is unknown. To address this question, we evaluated serial anti‐A and anti‐B antibody titers in 50 adult recipients. Donor‐specific antibody titers remained low (≤1:4) in 42 recipients (84%). However, antibodies against nondonor blood group antigens were continuously produced in recipients with blood type O. We stimulated recipients' peripheral blood mononuclear cells in vitro to investigate whether B cells produced antibodies against donor blood group antigens in the absence of graft adsorption in vivo . Antibodies in cell culture supernatant were measured using specific enzyme‐linked immunosorbent assays ( ELISAs ). Thirty‐five healthy volunteers and 57 recipients who underwent ABO ‐compatible LKT x served as controls. Antibody production in vitro against donor blood group antigens by cells from ABO i LKT x patients was lower than in the control groups. Immunoglobulin deposits were undetectable in biopsies of grafts of eight recipients with low antibody titers (≤1:4) after ABO i LKT x. One patient with blood type A1 who received a second ABO i LKT x from a type B donor did not produce B‐specific antibodies. These findings suggest diminished donor‐specific antibody production function in the setting of adult ABO i LKT x.