The following factors contributed to a faster immune recovery: peripheral blood as a stem cell source and reactivation of CMV infection for CD3<sup>+</sup> and CD4<sup>+</sup> lymphocyte subpopulations; reactivation of CMV infection for CD8<sup>+</sup> subset; donor EBV-IgG<sup>+</sup> and no EBV reactivation for CD19 lymphocytes; recipient age below 10 years and peripheral blood as a stem cell source for NK cells.
Factors associated with lower CD19+ B cell levels were as follows: aGVHD grades II-IV had a trend to affect CD19+ B cell reconstitution at +180 days; clinically extensive cGVHD was significantly associated with CD19+ B cell deficiency at +360 days and serum IgG level at +180 and +360 days; cytomegalovirus (CMV) infection occurred after +38 days was correlated with lower B cell level at both +90 and +360 days, while those occurred before +38 days did not show this effect; glucocorticoids used around +90 and +180 days was associated with lower CD19+ B cell levels at +90 and +360 days, respectively, especially in patients that did not experience extensive cGVHD.
To investigate if delayed immune recovery was a potential risk factor, the recovery of the CD3(+), CD4(+), CD8(+) and CD19(+) cells was related retrospectively to genotypic detected resistance development in three pediatric patients with ganciclovir (GCV)-resistant human cytomegalovirus (HCMV)-infection out of 79 receiving allogeneic PBSCT.