Rituximab induces CD20 relocalization and A-SMase activation into raft microdomains. Daudi and RL cells were treated or not for 10 minutes with 10 μg/mL rituximab, after which raft microdomains were isolated as described in “Materials and methods.” (A) CD20 localization was determined by Western blot analysis using a mouse anti-CD20 antibody. (i) Light (fractions 1-3); (ii) rafts (fractions 4-6); (iii) intermediate (fractions 7-9); and (iv) heavy (fractions 10-12). (B) A-SMase activity was measured on each fraction after raft isolation as described in “Materials and methods.” Results are the mean of 3 independent experiments ± SD. (C) Daudi cells were treated with 10 μg/mL rituximab for 15 minutes, then localization of CD20, CER, and raft microdomains was determined as described in “Materials and methods” by confocal microscopy.