Poor immune reconstitution after four or five major HLA antigens mismatched T cell-depleted allogeneic and autologous stem cell transplantation.

Two adults with primary liver cancer underwent liver transplantation from 5/6 and 4/6 major HLA-antigen mismatched unrelated donors. They were then conditioned with 4 x 2 Gy of total lymphoid irradiation, 120 mg/kg cyclophosphamide, 7.5 Gy total body irradiation and anti-T cell antibodies. Thereafter, the patients received T cell-depleted autologous: unrelated mismatched bone marrow in a proportion of 0.5:3.0 and 0.35:1.1 x 10(6) CD34+ cells/kg, respectively. After allogeneic stem cell transplantation (ASCT), both became mixed chimeras, as determined with polymerase chain reaction amplification of variable number tandem repeats from DNA obtained from CD3+, CD19+ and CD45+ magnetic bead-separated cells. Due to a reduction in donor T cells, the first patient was given 10(5) donor T cells/kg and became a complete donor chimera within 3 months. The second patient rejected all donor cells within 1 month after ASCT. Leucocytes normalized in both patients within 1 month. CD8+ cells normalized after 4 and 2 months in the two patients, respectively. However, CD4+, CD56+ and CD19+ cells remained low, except for a transient increase in patient 2. Lymphocyte responses to mitogens were negative in patient 1 from 1 to 5 months after ASCT. This patient also showed an oligoclonal pattern of the B cell repertoire, performed by CDR3 spectratyping. Epstein-Barr virus DNA in lymphocytes increased by 4-5 log in both patients. Prior to ASCT, recipients and donors were mutually reactive in mixed lymphocyte cultures (MLC). In the first patient, who became a complete donor chimera, the chimera cells showed no response to recipient or donor, but a positive response to third party. In the other patient, recipient cells reacted vigorously against donor lymphocytes at the time of rejection. Both patients suffered from overwhelming bacterial, fungal and viral infections, and died of pneumonia 5 and 3 months after ASCT, respectively. To conclude, with a major HLA-mismatch barrier, stable mixed chimerism seems difficult to achieve. The first patient became a full donor chimera and the second one rejected the graft. Both suffered from immune incompetence.