Cellular localization of Syt IX, ARF1, and TGN38. (A) RBL-Syt IX⁺ (i-vi) and RBL-Syt IX⁻ (vii-viii) cells were transiently transfected with ARF1-GFP cDNA (i-ii,v-viii) or with HA-TGN38 cDNA (i-iv,vii,viii). Cells were grown on glass coverslips for 24 hours and either left untreated (UT) or treated with nocodazole (20 μM) for 2 hours, as indicated. Cells were subsequently labeled with monoclonal anti-HA antibodies (i-iv,vii-viii) or polyclonal anti–Syt IX antibodies (iii-vi) followed by Cy3- or FITC-conjugated donkey anti–mouse or anti–rabbit IgG as indicated. Bars represent 3 μm. (B) RBL-Syt IX⁺ cells were double labeled with polyclonal anti–Syt IX and monoclonal anti-TGN38 antibodies followed by FITC- or Cy3-conjugated donkey anti–mouse or anti–rabbit IgG. Bars represent 8 μm.