(A through F) shows the results of typical two-color flow cytometric analysis of a cell suspension obtained from C3H/HeN mice Peyer's Patches 24 hours after sham-CLP (sham)(A, C, E, G) or CLP (B, D, F, H; simultaneously stained and analyzed). (A and B) are histograms of cell number versus FITC-fluorescent intensity generated from the ungated populations stain either antibody to Fas antigen (solid black histogram) or isotypic antibody control (light gray overlayed histogram)(summary data for repeated experiments is provided in Fig 9A and B). The nonspecific/negatively (M1) stained cells were delineated from the Fas-antigen positively (M2) stained cells by the use of isotypic antibody controls. Similarly, B220⁺ cells were discriminated from B220- cells by using isotypic Cychrome antibody control. The percentage of cells expressing a given phenotype are given (C and D). Histograms (E and F) of cell number v Fas antigen fluorescent intensity produced from each of the B220 phenotypically defined populations, respectively, illustrate the typical changes observed in the frequency of Fas antigen positive cells encountered after CLP in the Peyer's patch cells (summary data for repeated experiments is provided in Fig 10).