Supplemental Materials

This article contains the following supporting material:

• Figure S1 - Ag presentation assays were performed as described in figure 1A but using either NP coupled to BCR-ligand (anti-IgG) (A) or to the Ag used (LACK or HEL) (B), only. Syk-sufficient and -deficient cells are not able to activate T cells under such conditions.
• Figure S2 - H2-DM and LAMP-1 localize to the same intracellular compartments in WT and ΔSyk cells. (A) 3-D reconstitutions of confocal images showing WT and ΔSyk cells activated with BCR polyvalent ligands for various time-periods, fixed and stained for the indicated markers. (B) Quantification of the experiment described in A using the Metamorph co-localization program shows a perfect match for H2-DM and LAMP-1 staining in both cell types (100-150 per condition, two independent experiments).
• Movies S1 - Time-lapse experiments performed on WT (S1) or ΔSyk (S2) cells activated with multivalent BCR ligands. Films were obtained from a z-stack acquisition of 4 planes acquired every 40 sec during 35 min, immediatly after BCR stimulation. Images were deconvolved and projected into a single image for each time point. WT cells show polarization of their actin cortex, actin filaments being concentrated at and extending from one cell pole. In contrast, Syk-deficient cells present a non-polarized and homogeneously distributed actin network.
• Movies S2 - Time-lapse experiments performed on WT (S1) or ΔSyk (S2) cells activated with multivalent BCR ligands. Films were obtained from a z-stack acquisition of 4 planes acquired every 40 sec during 35 min, immediatly after BCR stimulation. Images were deconvolved and projected into a single image for each time point. WT cells show polarization of their actin cortex, actin filaments being concentrated at and extending from one cell pole. In contrast, Syk-deficient cells present a non-polarized and homogeneously distributed actin network.