Immunological Recovery after Nonmyeloablative Transplant: A Prospective Study of 24 Patients Treated in a Single Center.

Background: Nonmyeloablative conditioning regimens are more and more widely used in the setting of stem cell transplant due to a reduced transplant related mortality. However, these conditioning regimens include more immunosuppressive agents and little data in terms of immunological recovery are found in the literature.

Population: 24 patients (pts) admitted for nonmyeloablative transplant from HLA identical donors were prospectively followed during a period of 1 year. All pts received a conditioning regimen consisting of rabbit ATG (fresenius), Fludarabine phosphate, Cyclophosphamide ( ARA-C for myeloid malignancies) cyclosporin A and mycophenolate mofetil (MMF). Lymphocytes markers expression as well as lymphocytes absolute numbers were studied to evaluate the cellular immunologic recovery. IgG, IgA and IgM levels were also monitored during one year. Pts were stratified according to the presence of GVHD(acute and chronic) or not.

Results: 24 pts with a median age of 52 (20–64) years old transplanted with an attenuated conditioning regimen, were evaluated. Median delay to recover 500 ANC and 20000 plt/ul was 8 days. Without GVHD, the pts recover a normal level of CD3, CD8, CD19,CD56 and CD45RO positive lymphocytes within 6 months. CD4+ and CD45RA + lymphocytes did not reach normal values within 1 year; Therefore the CD4/CD8 ratio remains low for more than 12 months. This observation explains the high incidence of oppotunistic infections in these pts even 6 months after transplantion. In our small seies,with or without GVHD neither IgA, nor IgM recovered within 1 year. IgG recovery is not evaluable because of human IVIG administration monthly after transplant.

Conclusion: our small series confirms the rapid hematologic recovery after nonmyeloablative transplant.Cellular immunological recovery without GVHD is achieved within 6 months for most of the lymphocytes subsets excepted the CD4+ lymphocytes who need more than 12 months to recover. IgM and IgA recovery is also very slow.