Splenocytes from mice immunized against hMOR are sensitized to CD95-mediated apoptosis.

BALB/c mice were injected intraperitoneally with either PBS (n = 8), CHO cells (n = 10), or recombinant hMOR/CHO cells (n = 10). Mice were injected 9 times, with a 2-week interval between each injection. Panel A shows, for one representative mouse from each group, the DNA content of nuclei of splenocytes incubated for 24 hours in the absence (i) or presence of 5 μg/mL of either hamster anti-KLH IgG mAb (clone Ha4/8) (ii) or hamster anti-CD95 IgG mAb (clone Jo2) (iii). DNA content of nuclei was analyzed by cytofluorometry after incubation of the cells in hypotonic medium containing propidium iodide. Each experiment was performed at least in duplicate. The percentage of subdiploid DNA content is indicated. The arrow indicates nuclei with subdiploid DNA content typical of apoptosis. Panel B depicts the anti-Fas antibody–induced apoptosis of splenocytes from each mouse injected with PBS (○), CHO cells (▵), or hMOR/ CHO cells (■). Basal apoptosis of splenocytes in the absence or presence of hamster anti-KLH IgG mAb was 7% ± 3%. One-way analysis of variance was used for statistical analysis.