Acute lymphoblastic leukaemic in two boys relapsed after engraftment of marrow from siblings identical at HLA A, B, and D loci but went into remission during subsequent graft-versus-host reactions without specific anti-leukaemia therapy. Later leukaemic relapse was primarily in extramedullary sites, with little or no involvement of bone-marrow, liver, or spleen. Cytogenetic studies in both cases showed that the relapsed leukaemic blasts were those of the recipients while marrow cells and blood lymphocytes detected during marrow remission originated from the female donors. Blood lymphocytes from one of the recepients kiled. 51Cr-labelled autologous lymphoblast. The prolonged bone-marrow remission in the face of active and even massive extramedullary leukaemia suggests a graft-versus-leukaemia reaction in these two patients VSports手机版. .