Immunoglobulin A and secretory immunoglobulin A in the bronchoalveolar lavage from patients after lung transplantation.

Secretory immunoglobulin A (sIgA) is the most important Ig on mucosal surfaces. In bronchoalveolar lavage (BAL) fluid, sIgA is mainly produced by bronchus-associated lymphoid tissue (BALT). The presence of pre-formed antibodies against donor tissue in kidney transplantation is associated with hyperacute rejection, indicating a humoral (antibody-mediated) reaction. In heart and liver transplantation, humoral rejection has also been documented. The goal of this study was to evaluate the role of IgA in patients after lung transplantation. An enzyme-linked immunosorbent assay was established to determine the levels of sIgA, IgA, and total protein in the lavage. IgA and sIgA were both detectable in BAL from transplanted lungs. IgA and sIgA levels were both higher during episodes of infection than during episodes of rejection or during the control episodes. The level of IgA during episodes of rejection equaled the level of IgA during the control episodes. The level of sIgA was significantly decreased during episodes of acute rejection (1.8 +/- 1.0 microg/mL) when compared with the control (7.2 +/- 1.0 microg/mL; p = 0.013). This study demonstrates that BALT retains the ability to produce Ig even after lung transplantation. The levels of IgA and sIgA and their ratio do not contribute to the differentiation between rejection and infection in lung-transplanted patients.