Down-regulation of cell-surface Fas and FasL in early erythroblasts from β-thal mice. (A) Representative flow cytometric histograms showing an example of the changes found in erythroblast frequencies within Ter119⁺ cells in spleen in a β-thal mouse compared with a littermate wild-type mouse. (B) Representative flow cytometric histograms of Fas and FasL expression in spleen Ery.A, B, and C, in β-thal erythroblasts, and in erythroblasts from a wild-type littermate. The percentage of Ery.A positive for Fas relative to FMO control (not shown) is shown in red. The percentage of Ery.B positive for Fas is shown in blue. (C-D) Changes in erythroblast subset frequencies, and in Fas and FasL expression, in spleen (C) and bone marrow (D), in β-thal mice (n = 8) compared with littermate wild-type mice (n = 8). Data are mean ± SEM. Spleen and bone marrow cells were analyzed as illustrated in panels A-B. ^*P < .05, ^**P < .01, ^***P < .001, ^****P < .001.