EXPRESSION AND REGULATION OF ADHESION MOLECULES BY GAMMA-DELTA T-CELLS FROM LYMPHOID-TISSUES AND INTESTINAL EPITHELIUM

T cells bearing the gamma delta T cell receptor localize largely in ep ithelial tissues, but are also present at low frequency in organized s econdary lymphoid organs. To assess the role of cell surface adhesion molecules in the traffic and tissue localization of gamma delta T cell s, we compared the expression of these molecules on both alpha beta an d gamma delta T cells in several lymphoid and non-lymphoid organs. In the gut epithelium, gamma delta cells express less LFA-1 (CD11a), Pgp- 1 (CD44), and alpha 4 integrin than the corresponding up cells. In lym ph nodes (LN) and Peyer's patches (PP), adhesion molecule expression b y gamma delta cells is heterogeneous, with some of the cells having a phenotype similar to that of intraepithelial gamma delta cells and the rest expressing high levels of CD44 and L-selectin (CD62L) but lower beta 7 and alpha(M290), a phenotype more like lymph node up cells. The refore, the particular set of adhesion molecules expressed by a T cell is dependent, in part, on its anatomic location. Superimposed upon th is, however, are differences in expression that are based on the type of T cell; LN and PP gamma delta T cells express less CD44 but much mo re beta 7, alpha(M290) and ICAM-1 (CD54) than alpha beta T cells in th e same organ. The differences in adhesion molecules between alpha beta and gamma delta cells are not due simply to differences in their acti vation status, because these molecules are regulated differently after activation through the T cell receptor (TcR)/CD3 complex. The differe ntial expression of adhesion molecules on cells bearing a particular T cR V region suggests that distinct adhesion phenotypes may arise from prior contact with specific antigen and resultant cell activation in v ivo. Lastly, the presence of high level expression of alpha 4 beta 7 a nd alpha(M290) on L-selectin(lo) gamma delta cells in lymph nodes sugg ests that these gamma delta cells may be uniquely capable of migrating to the gut. The differences in adhesion molecule expression and regul ation between gamma delta and alpha beta T cells could explain, in par t, the distinct homing and tissue localization of these T cell subsets in vivo.