CAMPATH-1G IN-VIVO CONFERS A LOW INCIDENCE OF GRAFT-VERSUS-HOST DISEASE-ASSOCIATED WITH A HIGH-INCIDENCE OF MIXED CHIMERISM AFTER BONE-MARROW TRANSPLANTATION FOR SEVERE APLASTIC-ANEMIA USING HLA-IDENTICAL SIBLING DONORS

We have evaluated the effect of in vivo Campath-1G on engraftment and GVHD in 23 patients with severe aplastic anaemia transplanted from HLA -identical sibling donors, In 14 patients Campath 1G was given pretran splant for up to 9 days in an attempt to overcome graft rejection (gro up 1), In nine patients Campath-1G was given pre-transplant, but also continued post-transplant until day +5 to reduce GVHD (group 2), There were three patients with late graft failure in group I following init ial neutrophil engraftment, and four cases of grade II+ GVHD, In group II, two patients had early graft failure (no take), and there were no cases of acute GVHD out of seven evaluable patients, One patient in g roup I developed chronic GVHD of the liver, and two patients (one in e ach group) had transient localised chronic GVHD, PCR of short tandem r epeats was used to evaluate chimaeric status in 13 patients, Of 11 pat ients with initial neutrophil engraftment, only one had 100% donor hae mopoiesis at all times, The remaining patients had either transient mi xed chimaerism or persistence of recipient (<20%) cells, We conclude t hat in vivo Campath-1G is associated with a high incidence of mixed ch imaerism which tips the balance away from GVHD but towards graft rejec tion.