T cells from CD28-SA–treated donors specifically kill alloantigen-expressing target cells with similar efficiency as do T cells from PBS-treated donors. (A) Experimental design. FACS indicates fluorescence-activated cell sorting. (B) Representative dot plots used for identifying the different indicator cell populations at the end of the in vivo killing assay are shown. (C) Circles represent individual animals and the horizontal bars the median values with 5 animals per group (T cells [PBS], n = 4). (D) The spleens of mice that had been transferred with T cells from either PBS- or CD28-SA–treated donor mice harbored similar numbers of donor CD90.1⁺ CD8⁻ and CD90.1⁺ CD8⁺ T cells at the time of the analysis of the killing assay. The experiment has been repeated with in vitro CD28-SA–activated T cells rendering similar results.