CD8 and CD103 are highly expressed in asthmatic bronchial intraepithelial lymphocytes

Although characteristics of intraepithelial lymphocytes (IELs) in mucosal immunity have been well defined in the intestine, bronchial IELs have been little investigated. Recently, we showed that bronchial IELs have a distinct function that partly resembles that of intestinal IELs; however, surface antigen expression of bronchial IELs and the relationship of that expression to airway disease have not been studied.

We analyzed phenotypic profiles of human bronchial IELs and lamina propria lymphocytes (LPLs) by double-staining immunohistochemistry using full-thickness bronchial specimens (10 nonasthmatic controls and 7 asthmatics) from lung resections.

In controls, the percentage of CD4+ cells was lower, and the percentage of CD8+ cells was higher in IELs compared to LPLs (CD4: median 50.0% in IELs vs. 65.9% in LPLs, p = 0.01; CD8: 50.9% in IELs vs. 34.4% in LPLs, p = 0.007). The percentage of cells positive for CD103 (αE-integrin) was higher in IELs than that in LPLs (median 60.1% in IELs vs. 16.9% in LPLs; p < 0.001). In IELs from asthmatics, these characteristics were particularly significant (CD4: median 26.2%, p = 0.008; CD8: 79.8%, p = 0.007; CD103: 76.2%, p = 0.019; all compared with IELs from nonasthmatics).

These results suggest that human bronchial IELs have roles distinct from subsets of other lymphocytes, and that CD8+ cells and CD103+ cells have potentially important functions in the bronchial epithelium.