Characterizing the antigenic profile of the human trachea: Implications for tracheal transplantation

Background. Tracheal transplantation may be a viable alternative in select situations of long-segment tracheal stenosis. Issues concerning human tracheal antigenicity and the requirement for systemic immunosuppression need to be addressed. This study examined the distribution of the major transplantation antigens on fresh human trachea. Methods. Frozen sections of 10 human tracheas were examined for class I (HLA [human leukocyte antigen]- A, -B, -C) and class II (HLA-DR) histocompatibility antigens using mouse monoclonal antibodies in an indirect immunoperoxidase assay. The tracheal mucosa, perichondrium, cartilage matrix, and chondrocytes were examined and assigned a semiquantitative score for HLA class I and class II expression. Results. The tracheal mucosa was strongly antigenic for HLA class I and class II antigens, whereas the perichondrium contained only scattered fibroblasts that were positive for both classes. The polysaccharide matrix was consistently devoid of class I or class II expression. The chondrocytes of all 10 specimens expressed diffuse class I positivity; only two specimens contained chondrocytes that expressed class II positivity. Conclusions. The human trachea contains 'compartments' of highly antigenic tissue that are morphologically distinct from regions of lesser antigenicity.