Immunoglobulin Levels and Occurrence of Infections After Lung Transplantation and Impact of IgG Replacement

Immunosuppressive therapies have led to remarkable improvements in survival in lung transplantation (LT) patients. However, one important adverse effect of these therapies has been the increasing emergence of hypogammaglobulinemia (HGG) which has been previously seen mostly in patients with primary immunodeficiency (PID). The goal of treatment of HGG in PID has been to maintain the trough IgG level above 500 mg/dl which might provide better protection against infections than do lower IgG serum concentrations. Although IgG therapy is of substantial benefit, the doses and trough levels of IgG that are optimal are not yet clearly established. The impact of high versus low IgG dosing on the frequency and severity of infections and rejection has not been studied before in LT patients with HGG. The specific aims for this study are to compare the incidence of infections in lung transplant recipients receiving higher versus lower dose of SQ IgG and to compare the incidence of infections in lung transplant recipients with mild hypogammaglobulinemia versus normal IgG levels. This study will be a single center study of all lung transplant recipients, age 18 years or older, at the University of Pittsburgh Medical Center (UPMC), with a randomized treatment arm and an observational arm. The hypotheses for the research study are: * Therapy with IV or SQ IgG is of substantial benefit in reducing the number of infections in lung transplant recipients with severe hypogammaglobulinemia (IgG < 500) * A higher dose of SQ IgG, with subsequent higher trough IgG levels, may have a higher impact on the frequency and severity of infections and rejection episodes, compared to a lower dose of SQ IgG, with subsequent lower IgG trough levels * Lung transplant recipients with mild hypogammaglobulinemia ( IgG= 500-750) have a higher incidence of infections compared to patients with normal IgG levels