Cellular and humoral immune reconstitution after autologous peripheral blood stem cell transplantation (PBSCT)

Immune reconstitution after autologous peripheral blood stem cell transplantation (PBSCT) is of particular interest because of its importance for clinical outcome. Despite prolonged immunosuppression, especially of CD4(+) cells, few infections after neutrophil recovery occur. Only reactivation of varicella zoster virus (VZV) is more frequent in the first year after transplantation. From August 1997 to May 2001, we prospectively evaluated 38 patients prior to conditioning and during follow-up of 12 months post-transplant for virus antibodies [measles, mumps, rubella, polio, herpes simplex, varicella zoster, mononucleosis, cytomegalovirus (CMV)] and lymphocyte subpopulations by flow cytometry. CD3(+) T lymphocytes, CD8(+) T cells, and B-lymphocyte reconstitution in our study confirms previous reports. Complete CD4(+) lymphocyte reconstitution was not achieved in the 12 months post-transplant leading to a suppressed CD4/CD8 ratio. IgG antibody titers against measles, mumps, rubella, and polio were present in almost all patients pretransplant and during 12 months post-transplant, indicating persistent humoral immunity. CD3(+) and CD8(+) counts of patients with clinical VZV reactivation ( n=5) post-transplant were significantly higher (median: 1201/microl and 938/microl, respectively) than in patients without VZV reactivation (median: 594/microl and 482/microl, respectively) 6-12 months post-transplant. Positive CMV titers pretransplant ( n=19) were also correlated with higher CD3(+) and CD8(+) counts 3-6 months post-transplant (median: 1050/microl and 1056/microl, respectively) compared to CMV-negative patients (738/microl and 584/microl, respectively), although none of the patients suffered from CMV disease. Therefore, we conclude that persistent viral infections can contribute to the CD8(+) T-cell reconstitution after PBSCT by oligoclonal expansion of antigen-specific memory CD8(+) T cells.