Figure 7.

Fas localization to lipid raft microdomains in human memory T cells promotes susceptibility to Fas-induced apoptosis. (a) Cell death from activated human CD4⁺ T-cell subsets was calculated from annexin/PI staining, after treatment for 8 h either with anti-Fas IgG1 (bivalent) or anti-Fas APO-1-3 crosslinked with anti-IgG3 (crosslinked). Data are an average of nine different donors and error bars are ± S.E.M. (b) Immunoblot analysis of the distribution of Fas in sucrose gradient fractions of memory and naïve CD4⁺ T cells. Lck is shown as a positive control for raft localization (bottom immunoblot panels). Densitometry analysis of the percentage of Fas and Lck in each fraction is shown in the lower graphs. Data are an average ± S.E.M. of five independent experiments. (c) Effect of the palmitoylation inhibitor 2-bromopalmitate on susceptibility of naïve and memory CD4⁺ T cells to apoptosis triggered by either bivalent or crosslinked anti-Fas mAb for 8 h is indicated. Data are an average of two experiments done in triplicates ± S.E.M., ^*P<0.02, ^**P<0.009, ^***P<0.0001, paired Student's t-test