VCAM-1 inhibits neutrophil but not lymphocyte apoptosis. (A) CD31, ICAM-1, and VCAM-1 were immobilized at the concentrations shown (micrograms per milliliter) and neutrophils added for 18 hours before apoptosis was measured by DiOC₆ staining. Results are expressed as the percentage of apoptotic neutrophils compared with neutrophils cultured in medium alone; mean ± SD of 3 separate experiments. (B) VCAM-1 was immobilized in a 96-well plate, and neutrophils were added in the absence (□) or presence (▪) of 1000 U/mL IFN-β. After 18 hours, apoptosis was measured by DiOC₆ staining. (C) Cells from a CD4 T-cell line were incubated in the presence or absence of the survival factors IL-2 (50 U/mL), IFN-β (1000 U/mL), or sVCAM-1 (10 μg/mL). Apoptosis was measured by DiOC₆ staining. Data in panels B-C are from a single experiment that is representative of 3 performed.