Impact of hypogammaglobulinemia on bacterial infections after allogeneic hematopoietic cell transplantation

Background : Infections are major complications in patients with hematologic neoplasms. Humoral immunity plays a critical role in defense against pathogens. Although hypogammaglobulinemia can carry a risk of infection, there is no confirmed association between low immunoglobulin levels and bacterial infections after allogeneic hematopoietic cell transplantation. Methods : In this study, we assessed the association between different variables, including hypogammaglobulinemia, and the incidence of bacterial infections in 579 consecutive patients receiving allogeneic hematopoietic cell transplantation. Data obtained during three different periods post-transplantation (early, intermediate, and late) were analyzed retrospectively. Results: During the intermediate phase, the median serum trough level of IgG was significantly lower in patients with bacterial infections than in those without (5.39 vs. 6.00 g/L, respectively; p <0.01); however, there was no difference during the early (6.50 vs. 6.53 g/L, respectively; p =0.37) or late (8.60 vs. 9.30 g/L, respectively; p =0.53) phases. The incidence of bacterial infections during the intermediate phase fell as the serum IgG trough level increased (incidence rate ratio, 0.85; 95% confidence interval: 0.78–0.94, p <0.01). Hypogammaglobulinemia (incidence rate ratio, 1.70; 95% confidence interval: 1.11–2.62, p =0.02), as well as grade II–IV acute graft-versus-host disease (incidence rate ratio, 2.10; 95% confidence interval: 1.39–3.18, p <0.01), was significantly associated with bacterial infections solely during the intermediate phase. Conclusions: There was a significant association between hypogammaglobulinemia and bacterial infections solely during the intermediate phase post-transplantation. Immunoglobulin levels and recovery of innate immune cells may affect the incidence of bacterial infections.