Fas-induced apoptosis suppresses sVCAM-Ig binding to Jurkat cells.

Jurkat cells were untreated (A) or were treated with anti-Fas antibody CH11 (300 ng/mL) for 4 hours (B-D). 7 Ig-domain VCAM-Ig binding was assayed as described in “Materials and Methods” (A-C). (D) Cells were stained with the anti-α4-integrin mAb 9F10. Outer membrane phosphatidylserine exposure was assayed by PE-conjugated annexin-V binding, as described in “Materials and Methods”. The percentage of cells in each quadrant is indicated. Note the marked reduction in VCAM-Ig binding to annexin-V(+) cells (B) without a major reduction in α4 expression (D). VCAM-Ig binding to annexin-V(+) cells is restored by the activating antibody 8A2 (C). 8A2 also markedly increased annexin-V binding to previously negative cells (C). (E) Kinetics of sVCAM-1 and annexin-V binding to Jurkat cells after anti-Fas antibody treatment was analyzed. Cells that bound VCAM-Ig (V+) or failed to bind VCAM-Ig (V−) are indicated. Similarly, annexin-V binding (A+) and nonbinding (A−) cells are also indicated. Note that the A(−)/V(−) cells initially increased coordinately with the decrease in A(−)/V(+) cells, before any increase in A(+) cells, and note the nearly complete absence of V(+)/A(+) cells, indicating that in apoptotic cells α4-integrin activation is blocked. Results are representative of 3 separate experiments.