PECAM-1 affects the rate and extent of apoptosis in human Jurkat T cells. Wild-type, PECAM-1⁺ Jurkat cells were FACS sorted through 6 rounds of anti—PECAM-1 antibody screening to enrich for cells negative for PECAM-1 expression, finally yielding the PECAM-1⁺ (A) and PECAM-1^- (B) Jurkat cell lines shown. A PECAM-1 cDNA expression vector or a vector control was transfected back into PECAM-1^- Jurkat cells to reconstitute genetically identical lines differing only in PECAM-1 expression (C-D) while retaining similar levels of Bax, Bcl-2, Mcl-1, Bcl-X_L, and SHP-2 (E). Upon exposure to varying doses of UV irradiation, PECAM-1^- Jurkat cells with enforced expression of PECAM-1 were found to be resistant to this proapoptotic stimulus, as judged by nuclear condensation (F-G). Original magnification, panel F: × 40. Data shown in panel G represent the mean ± the standard deviation of triplicate determinations.