Monotypic immunoglobulin E plasma cells in an allogeneic bone marrow transplant recipient.

A patient with acute lymphoblastic leukaemia in first remission received a bone marrow transplant from his HLA-identical brother. The patient had a remote history of asthma and the bone marrow donor had allergic asthma. The patient developed acute graft-versus-host disease and died 2 months after transplantation. At autopsy there were high numbers of plasma cells in lymphoid tissues. The majority of this cell population was of polytypic IgG, IgM or IgA origin, but there was a significant contribution by monotypic IgE-lambda-containing cells, varying from 10% in the appendix to 35% in lymph node. The serum IgE level in the patient was less than 0.5 IU/ml before transplantation, and 8.5 IU/ml 1 month thereafter. In the donor the value was about 400 IU/ml. In the donor only, specific IgE antibodies to various allergens were detectable. The bone marrow of the donor contained 0.4% plasma cells, of which 36% were IgE positive (chi/lambda ratio 1/11). These findings are compatible with literature data on elevations in serum IgE level following bone marrow transplantation. We suggest that the IgE-lambda plasma cell population is of donor origin.