Monocytotoxic antibodies after bone marrow transplantation in aplastic anemia

Pre- and post-transplant sera from 51 cases of bone marrow transplants performed for severe aplastic anemia were tested on monocytes (M) and corresponding B cells (B) from a panel of unrelated donors. One-third of the sera were cytotoxic for B and M either from different or from the same individuals, while 45% reacted only to M and appeared to recognize non-HLA M-associated antigens. No significant reaction to endothelial cells was obtained with these sera. The subsequent clinical course was not associated with any reaction pattern of pretransplant sera. There was a significant relationship between rejection and the development of M antibodies after grafting, but since these were also found in many other patients without rejection, their occurrence has no predictive value for an individual patient.