Expression and regulation of adhesion molecules by γδ T cells from lymphoid tissues and intestinal epithelium

Abstract

T cells bearing the γδ T cell receptor localize largely in epithelial tissues, but are also present at low frequency in organized secondary lymphoid organs. To assess the role of cell surface adhesion molecules in the traffic and tissue localization of γδ T cells, we compared the expression of these molecules on both αβ and γδ T cells in several lymphoid and non‐lymphoid organs. In the gut epithelium, γδ cells express less LFA‐1 (CD11a), Pgp‐1 (CD44), and α4 integrin than the corresponding αβ cells. In lymph nodes (LN) and Peyer's patches (PP), adhesion molecule expression by γδ cells is heterogeneous, with some of the cells having a phenotype similar to that of intraepithelial γδ cells and the rest expressing high levels of CD44 and L‐selectin (CD62L) but lower β7 and α_M290, a phenotype more like lymph node αβ cells. Therefore, the particular set of adhesion molecules expressed by a T cell is dependent, in part, on its anatomic location. Superimposed upon this, however, are differences in expression that are based on the type of T cell; LN and PP γδ T cells express less CD44 but much more β7, α_M290 and ICAM‐1 (CD54) than αβ T cells in the same organ. The differences in adhesion molecules between αβ and γδ cells are not due simply to differences in their activation status, because these molecules are regulated differently after activation through the T cell receptor (TcR)/CD3 complex. The differential expression of adhesion molecules on cells bearing a particular TcR V region suggests that distinct adhesion phenotypes may arise from prior contact with specific antigen and resultant cell activation in vivo. Lastly, the presence of high level expression of α4β7 and α_M290 on L‐selectin^lo γδ cells in lymph nodes suggests that these γδ cells may be uniquely capable of migrating to the gut. The differences in adhesion molecule expression and regulation between γδ and αβ T cells could explain, in part, the distinct homing and tissue localization of these T cell subsets in vivo.