Kinetics of IgG subclasses and their effects on the incidence of infection after allogeneic hematopoietic stem cell transplantation.

BACKGROUND: The impact of the reconstitution of IgG subclasses after allogeneic hematopoietic cell transplantation (allo-HCT) on the outcomes is unclear. METHODS: We investigated the effects of stem cell source on the levels of serum IgG subclasses and their influence on the infection risk and prognosis. The levels of serum IgG, IgG2 and IgG4 were measured chronologically in 100 patients who underwent allo-HCT at our institute. RESULTS: The median levels of serum IgG, IgA and IgM and the number of total B-cells were determined up to one year after allo-HCT. The serum IgG2 levels decreased within one year. A multiple linear regression analysis identified lymphoid malignancy, cord blood, and days after allo-HCT as significant risk factors for low serum IgG2 levels. There were no significant differences in the level of IgG or IgG2 at 90 days after allo-HCT between the late bacterial infection group (≥90 days following allo-HCT) and the control group (P = 0.34 and 0.45, respectively). There was no significant impact of the IgG, IgG2 or IgG4 levels on the survival or non-relapse mortality. CONCLUSION: The results suggest that cord blood transplantation might affect humoral immune reconstitution, including the IgG2 level, after allo-HCT.