INTERACTION OF MOUSE THYMOCYTES AND A THYMOCYTE-LIKE CELL-LINE WITH THE ECM GLYCOPROTEIN ENTACTIN

Entactin, a sulfated glycoprotein of 150-kDa, is a component of the ex tracellular matrix that promotes the adhesion of numerous types of cel ls, including lymphocytes (Li and Cheung, J. Immunol. 149, 3174, 1992) , prompting us to question whether developing T lymphocytes in the thy mus (thymocytes) also interact with this molecule. We thus investigate d the adhesion of a thymocyte-like cell line (S49.1) to entactin, as w ell as the adhesion and migration of primary mouse thymocytes upon ent actin-coated surfaces. In dose-response and time-course experiments, a 50 mu g/ml coating concentration of entactin and a 60-min incubation period induced a high level (approximately 65-85%) of S49.1 cell adhes ion. Preincubation of the S49.1 cells in medium containing the metabol ic inhibitors sodium azide or a-deoxy-D-glucose inhibited adhesion to entactin 47.2 and 79.5%, respectively. Furthermore, performing the adh esion assay at 4 degrees C instead of at 37 degrees C inhibited S49.1 cell adhesion 27.1%. A high percentage (approximately 90-100%) of S49. 1 cells also bound to the lectin concanavalin A and to fibronectin, wh ile laminin promoted only 19.3% adhesion. Our adhesion assay (St. John eb al, J. Immunol. Methods, 170, 159, 1994) was then modified to perm it a comparison of S49.1 cell adhesion strength to entactin relative t o the other substrates. Consequently, concanavalin A promoted the stro ngest adhesion, followed by fibronectin and then entactin. In addition , high percentages (92,5, 63, and 75,9%, respectively) of primary thym ocytes from 4- to 5-week-old BALB/c mice adhered to entactin, Con A, a nd fibronectin, while much lower levels (7.6%) of adhesion to laminin were observed, Using a capillary tube random migration assay to measur e hapto-kinesis, entactin-, concanavalin A-, and fibronectin-coated su rfaces stimulated little migration, while laminin-coated surfaces enha nced thymocyte migration extensively. Since entactin promoted thymocyt e adhesion but affected migration only marginally, we suggest that thi s molecule may play a role in thymocyte localization during T cell dev elopment. (C) 1996 Academic Press, Inc.