FIGURE 5.

Autoantibodies from CIDP patient 3 specifically recognize contactin bearing mannose-rich N-glycans. N2a cells were co-transfected with contactin-GFP and Caspr (A) or transfected with contactin-GFP alone (B) and surface-labeled with purified IgGs from CIDP patient 3 (red). CHO Lec1 mutant cells transfected with contactin (C) or contactin-Ig (D) were surface-labeled with IgGs from CIDP patient 3 (C and D, red) and rabbit anti-contactin antibody (green). CHO Lec1 cells were transfected with contactin and surface-labeled with IgGs from patient 1 (E) and patient 2 (F). As schematized, contactin co-expressed with Caspr in N2a cells or contactin expressed in Lec1 cells bears mannose-rich N-glycans. In contrast, contactin expressed in N2a cells bears complex N-glycans. Only mannose-rich contactin was targeted by autoantibodies from CIDP patient 3. G and H, N2a transfected with Caspr and contactin (G) and Lec1 cells transfected with contactin alone (H). Preincubation of IgGs from patient 3 with 20 μm oligomannose-5 did not prevent surface labeling. Bar, 10 μm.