Phenotypic assessment of the percentage of Fas+ cells indicates that marked augmentation of Fas antigen expression is present in the Peyer's patch cells is confined primarily to the B220⁺ (B-lymphocytes) subpopulation but not the B220- of cells harvested from septic (CLP) C3H/HeJ mice. Significance indicated by * at P< .05 v sham, Mann-Whitney U test; mean ± SEM; n = 5 to 6 mice sampled/group.