Diagnosis of lung allograft rejection by bronchial intraepithelial Leu-7 positive T lymphocytes

Currently there is no reliable technique for the diagnosis of lung allograft rejection. The presence of intraepithelial lymphocytes expressing the Leu-7 antigen is a specific marker of renal rejection. We examined whether immunoperoxidase techniques that detect Leu-7 positive lymphocytes could be used to diagnose lung rejection in heart-lung transplant recipients. In lungs from two autopsied patients with lung allograft rejection, numerous Leu-7 positive lymphocytes were present in the donor bronchial mucosa (32 and 65 cells/section), submucosa (23 and 80 cells/section), and submucosal glands (7 and 19 cells/section). These Leu-7 positive lymphocytes were associated with proximal airway injury, including squamous metaplasia, destruction of submucosal glands, and ulceration. In one case, there was bronchiectasis. Both cases also had distal airway bronchiolitis obliterans. In contrast, Leu-7 positive lymphocyts were not identified in the epithelium of the native trachea of these two patients; nor were they found in the bronchial epithelium of two sets of transplanted lungs without evidence of rejection. Only rare Leu-7 positive lymphocytes were evident in the epithelium (0 to 2 cells/section) and submucosal glands (0 to 1 cell/section) of 20 lungs from autopsied patients who had not received a transplant. Application of this technique to epithelial biopsy specimens obtained at bronchoscopic examinations demonstrated that it could be applied to the diagnosis of rejection in living heart-lung transplant recipients.