ILT5-specific antibodies arise from disparities in the ILT5 protein. (A) G106 does not react with autologous DCs. mdDCs (donor derived) generated from patient G106 were probed with serum G106/1 (left panel, gray histogram) and a murine anti-ILT5 antibody (right panel, gray histogram). Reactivity of a control serum (left panel) or the isotype control antibody (right panel) is depicted as open histograms. (B) G106/1 reacts with recipient-derived ILT5 but not donor-derived ILT5. The ilt5 products of the recipient G106 (pretransplantation; alleles 1 and 2) and posttransplantation (donor-derived; ilt5v2 and v2b) were cloned and expressed on Bw cells. The transfectants were probed with an ILT5-PE mAb (left panels), a healthy control serum (middle left panels), serum G106/1 (middle right panels), and donor serum (right panels) shown as gray histograms. Reactivity of anti–ILT5-PE mAb and sera to untransduced Bw cells is depicted as open histograms. Bound human sera were detected with PE-labeled goat anti–human IgG (Fcμ-specific) antibodies. (C) Alignment of the deduced amino acid sequence of ilt5v1 and ilt5 variants derived from patient G106 pretransplantation (ilt5 recipient alleles 1 and 2) and posttransplantation ILT5 donor alleles 1 (= ilt5v2) and 2 (= ilt5v2b).