HS1 absence affects migration, adhesion, and homotypic aggregation. (A) Spontaneous migration after 4 hours on transwell (pore size 5.0 μm) of CNTR and HS1 KD cell and (B) WT and HS1^−/− mice purified B splenocytes (6 animals/group) is shown (*P ≤ .05; **P ≤ .01; ***P < .001). (C) Adhesion was quantified as mean fluorescence intensity (MFI) values for CNTR and HS1 KD cells and (D) as adhesion index for WT and HS1^−/− mice B cells (*P ≤ .05; **P ≤ .01; ***P < .001). (E) CNTR and HS1 KD cells adhesion on a HS-5 stroma cell layer after 2 hours of coculture was acquired with Nikon TS100 microscope with the use of a 10× dry objective. (F) Immunoprecipitation experiments with the use of anti–P-Tyr on CNTR and HS1 KD cells before and after anti-IgM stimulation and WB analysis for Vav1 (top) and HIP-55 (bottom). Total lysates are shown as control. (G) Rac1/2 activation assay was performed as pull-down on CNTR and HS1 KD cells (positive controls were provided with the kit). Total lysates were also used to detect Rac1/2 expression.