Late onset haemolysis and red cell autoimmunisation after allogeneic bone marrow transplant.

We reviewed the medical records of 293 patients who underwent allogeneic bone marrow transplants at the Hammersmith Hospital between 1989 and 1994. There was clinical evidence of an autoimmune reaction against red cells in nine patients. Seven of these patients had significant haemolysis; the other two had red cell autoagglutination. Haemolysis was resistant to treatment in three cases. Six of the nine patients had monoclonal Ig bands identified within 1 year of transplant. The autoimmune reaction could be classified broadly into two types: an early onset type (n = 4) beginning 2 to 8 months post-transplant associated with a cold antibody, and a late onset type (n = 5) beginning 6 to 18 months post-transplant associated with warm antibodies. The predominant antibody in the two categories described may reflect the kinetics of immune reconstitution post-transplant, since serum IgM levels typically return to normal 2 to 6 months post-transplant, while IgG levels may not reach normal levels until 12-18 months post-transplant. We speculate that unbalanced reconstitution of B and T cell lymphopoiesis post-transplant may favour emergence of oligoclonal proliferation and that some of the resulting antibodies may have activity against red cells.