DIFFERENTIAL SOLUBLE INTERLEUKIN-2R LEVELS IN BILATERAL BRONCHOALVEOLAR LAVAGE AFTER SINGLE-LUNG TRANSPLANTATION

Preliminary reports suggest that measurement of the soluble 55 kd subu nit of the interleukin-2 receptor may facilitate the diagnosis of allo graft rejection in solid organ transplants. Levels of soluble interleu kin-2 receptor in serum or plasma have previously lacked sufficient se nsitivity and specificity for the diagnosis of acute allograft rejecti on. Because single lung transplantation is preferentially performed fo r nonseptic end-stage pulmonary and cardiopulmonary maladies, we quest ioned whether the pattern of soluble interleukin-2 receptor recovery i n bronchoalveolar lavage fluid obtained from both the native and trans planted lungs may enhance correct diagnosis. Fifty-three consecutive f iberoptic bronchoscopic procedures were performed with bilateral bronc hoalveolar lavage fluid. Transbronchoscopic biopsies were histological ly classified by the International Society for Heart Transplantation W orking Formulation for Standardized Nomenclature. ''Soluble interleuki n-2 receptor index'' was calculated as the quotient of soluble interle ukin-2 receptor (in units per milliliter) by enzyme-linked immunosorbe nt assay, divided by protein (in milligrams per milliliter) to correct for differences in bronchoalveolar lavage fluid techniques and cellul arity. Soluble interleukin-2 receptor indexes were significantly incre ased in the allograft bronchoalveolar lavage fluid during histologic g rade A (acute rejection) versus normal transbronchoscopic biopsy speci mens (3395 +/- 1298 U/mg versus 76 +/- 21 U/mg) associated with an inc reased transplanted/native lung ratio (69.9 +/- 46 versus 2 +/- 1 [mea n +/- standard error of the mean]) (one-way analysis of variance, p < 0.01). Soluble interleukin-2 receptor indexes for transplanted and nat ive lungs and transplanted/native lung ratio could not differentiate h istologic grade B, normal, cytomegalovirus, or bacterial pneumonia. Pa tients with histologic grade C (obliterative bronchiolitis) status had no statistically significant increase in soluble interleukin-2 recept or indexes compared with patients with normal conditions. We conclude that further investigation of bilateral bronchoalveolar lavage fluid s oluble interleukin-2 receptor levels may improve accuracy of diagnosis after single lung transplantation. Furthermore, other cytokines or me chanisms are likely involved in episodes of acute pulmonary allograft rejection, as well as in obliterative bronchiolitis.