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J. Exp. Med.,
Volume 189, Number 6, March 15, 1999 979-990
By


From the * Division of Rheumatology and Clinical Immunology, Jichi Medical School, Tochigi
329-04, Japan; and the In extravasation of T cells, little is known about the mechanisms of transendothelial migration
subsequent to the T cells' tight adhesion to endothelium. To investigate these mechanisms, we
developed a monoclonal antibody (mAb), termed anti-4C8, that blocks transmigration but not
adhesion in a culture system in which high CD26-expressing (CD26hi) T cells preferentially
migrate through human umbilical vein endothelial cell (HUVEC) monolayers cultured on collagen gels. Anti-4C8 reacted with all CD3+ T cells and monocytes but not neutrophils or HUVECs. The structure defined by this antibody was an 80-kD molecule. The mAb at 1 µg/ml inhibited 80-90% of migration of CD3+ T cells through unstimulated and interferon
Second Department of Physiology, Osaka City University Medical School,
Osaka 545, Japan
-stimulated HUVEC monolayers without interfering with adhesion and cell motility. When added to
the cultures after the adhesion, anti-4C8 completely blocked subsequent transmigration of adherent T cells. Phase-contrast and electron microscopy revealed that T cells are arrested at the
intercellular junctions of HUVECs in the presence of anti-4C8. Anti-4C8 exhibited agonistic
effects on resting T cells without other stimuli under culture conditions in which anti-4C8 can
stimulate T cells. First, in the checkerboard assay using collagen gels, the antibody promoted
chemokinetic migration of the cells in a dose-dependent manner from 0.1 to 10 µg/ml. The
predominant population of T cells that migrated into collagen gels with impregnated anti-4C8 were CD26hi. Second, solid-phase-immobilized anti-4C8 induced adhesion of T cells to the
substrate, often with polarizations in cell shape and large pseudopods rich in filamentous (F-)
actin. Third, soluble anti-4C8 augmented F-actin content preferentially in CD26hi T cells
when added to T cells at a high dose of 10 µg/ml. Finally, both anti-4C8-induced chemokinetic migration and transendothelial migration were inhibited by pretreatment of T cells with
pertussis toxin. These findings suggest that stimulation via the 4C8 antigen increases cell motility of CD26hi cells with profound cytoskeletal changes through signaling pathways including G
proteins. The 4C8 antigen may be involved in preferential transmigration of CD26hi cells adherent to HUVECs.
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