MHC CLASS-II AND ICAM-1 EXPRESSION AND LYMPHOCYTE SUBSETS IN TRANSBRONCHIAL BIOPSIES FROM LUNG-TRANSPLANT RECIPIENTS

The expression of MHC class II antigens and ICAM-1 and the composition of lymphocyte infiltrates have been studied in frozen sections of tra nsbronchial biopsies from lung transplant recipients. First, biopsies obtained from patients who showed acute rejection, OB, and normal feat ures were compared. Second, we compared first-year biopsies from patie nts developing OB and patients with a good clinical outcome. HLA-DR wa s widely expressed on epithelia and vascular endothelium. Increased va scular HLA-DP expression was found in OB biopsies. In OB patients ther e was a significantly increased frequency of bronchial HLA-DP and vasc ular HLA-DQ expression. Expression of ICAM-1 by bronchial and bronchio lar basal cells, a phenomenon not reported previously in humans, was s een in a small number of biopsies. CDS predominant lymphocytic infiltr ates were present in all groups and were increased in OB biopsies and OB patients. Increased numbers of CD4-positive cells were found in rej ection and OB when compared with normal biopsies. These findings suppo rt an immunological basis for the development of OB.