AAT does not inhibit the 20S enzymatic activity of the proteasome. CD4+ T cells were obtained and treated as in Figure 2. The cells were then lysed, the A) cytoplasmic or B) nuclear fraction obtained and the proteasomes immunoprecipitated using Ab directed against the 20S subunit. The precipitated complexes were washed and tested for 20S proteasomal activity as indicated in Materials and Methods. The data are presented as box plots where the thick horizontal lines represent the median, the box extensions (whiskers) represent the data range and the box itself covers from the 25th to the 75th percentile. The data depicted are representative of 3 independent experiments. T, lysates of untreated T cells; T+IP, immunoprecipitation of 20S subunit from lysates of untreated T cells; T+AAT+IP, immunoprecipitation of 20S subunit from lysates of AAT (5 mg/ml) treated T cells; T+AAT+IP+AAT, immunoprecipitation of 20S subunit from lysates of AAT (5 mg/ml) treated T cells with additional AAT (5 mg/ml) added after precipitation. No significant change in 20S enzymatic activity was observed (cytoplasmic protein, p<0.50; nuclear protein p<0.55).