Identification of binding sites of ILT5-specific antibodies. (A) Scheme of chimeric ILT5v1/v2 molecules representing amino acids 3 to 278 (ILT5-C1), 150 to 278 (ILT5-C2), and 324 to 350 (ILT5-C3) of ILTv1. (B) Plasmids encoding ILT5 chimeras C1 to C3 and ILT5v1 were retrovirally expressed on Bw cells and tested with serum G106/1 (gray histograms). Reactivity of serum G106/1 with untransduced Bw cells is depicted as open histograms. (C) Bw cells expressing ILT5v1 were stained with serum G106/1 preincubated with Bw cells or Bw cells expressing ILT5 chimera (C1-C3) or ILT5v1 as indicated. Percentage reduction of reactivity compared with control Bw treated serum is shown.