Effect of incubation or endocytosis/re-expression on sIgD signaling. Cells were either untreated (A-D) or treated (E-H) treated with polyclonal goat anti–L chain F(ab′)2. The change in the ability of untreated cell populations to respond to ligation of sIgD was monitored over time in cases previously designated as (A,C,E,G) “responders” or (B,D,F,H) “nonresponders” to sIgM ligation. In parallel, (C-D) the level of expression of sIgD (MFI) was measured. Antibody-treated cell populations from “responders” or “nonresponders” underwent endocytosis of sIgD. (E-F) The ability of cell populations to reacquire signaling capacity or (G-H) sIgD expression was monitored. Unmutated cases have open symbols and mutated cases have filled symbols. Circled symbols in panels E-H indicate values at 72 hours for untreated cultures. Case numbers were as follows: “Responders” (A,C,E,G): 255 (□), 191 (▴), 269 (•), 273 (▪), 189 (♦), 231 (△), and 239 (▪). “Nonresponders” (B,D,F,H): 236 (•), 169 (large ♦), 159 (△), 153 (▪), 261 (▴), 201 (□), and 299 (small ♦).
