The generation of ABO hemagglutinins was used as a model to assess the tempo of reconstitution of antibody responses in recipients of elutriated (CCE) and nonelutriated (nonCCE) HLA matched bone marrow allografts. The study included 29 CCE recipients (10 major, 6 minor, and 1 major/minor ABO-mismatched, and 12 ABO-matched) and 40 nonCCE recipients (14 major, 12 minor, 2 major/minor, and 12 matched). Plasma volume in the graft and in blood product transfusions was uncorrelated with changes in hemagglutinin titers and therefore was excluded as a significant source of antibody. Removal of graft lymphocytes by CCE did not result in prolongation of host-derived hemagglutinins in recipients of major ABO-mismatched grafts. However, CCE resulted in a complete abrogation of the adoptive transfer of donor-derived antibody as detected in recipients of minor ABO-mismatched grafts. Despite the absence of adoptively transferred donor immunity in recipients of CCE grafts, they had hemagglutinin levels comparable with those of recipients of nonCCE grafts by 6 months after transplantation. This demonstrates that recipients of elutriated marrow were competent to mount de novo responses at that time. The strong correlation between donor pretransplant hemagglutinin titer and recipient titer 1 year after bone marrow transplantation in recipients of nonCCE grafts suggests that even late after transplant, antibody remains the product of adoptively transferred memory cells in recipients of grafts containing large numbers of mature lymphocytes.

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