High frequency of graft-versus-host-like syndromes following syngeneic bone marrow transplantation.

Occurrence of acute graft-versus-host reactivity-like (GvHR) syndromes has been shown in at least 3 and possibly in 4 further cases of 9 patients with bone marrow transplants from identical twin donors. The diagnosis of GvHR-like syndromes is based on clinical, immunologic, and histologic features indistinguishable from those observed in graft-versus-host disease (GvHD) grades I-III of patients receiving allogeneic major histocompatibility complex (MHC) matched bone marrow transplants. Induction of GvHR-like symptoms appeared to be correlated with reactivated viral infections after bone marrow transplantation (BMT) or, like in animal models, was due to specific conditioning therapy with cyclophosphamide. The high incidence of acute GvHR-like syndromes in the first months after syngeneic BMT suggests inability of the immune system to discriminate appropriately self from nonself antigens during a normal tolerance induction period after grafting.