Analysis of CSF IgG immunoreactivity in MS patients by protein expression arrays. (A) Incubation of the protein expression array with CSF from a representative MS patient (left) and a control donor (right). A 3 cm × 3 cm section of the 24 cm × 24 cm array is shown. IgG immunoreacitivity of the MS CSF to the expression clone B3 (spotted in duplicate) is marked by a circle. IgG concentration was adjusted to 1 mg/l IgG in MS and control CSF. (B) Western blot with purified protein B3. Immunoractivity was observed in the CSF of a representative MS patient (left) but not the NIND (middle) or OIND (right) control donors. All CSF samples were adjusted to 10 mg/l IgG. IgG binding was developed with ECL. M, molecular weight marker. (C) Analysis of immunoreactivity to B3 protein (left) and control protein GAPDH (right) with CSF (1:5 diluted) of 132 MS patients and 125 NIND patients by ELISA. Antibody titers were significantly higher in MS patients. Dot points represent the OD of a single CSF sample. Cut-off point, OD > 0.3 (mean ± 6 SEM). (D) CSF from a patient with high immunoreacitivty to patterns I and II proteins was separated by IEF and blotted against proteins B3, C6, C5, F4, and G4 as well as the control protein GAPDH. Binding of proteins from both patterns was similar with little overlap between the patterns. Similar results were obtained with CSF from another patient (data not shown). (E) IEF immunoblot with CSF (C) and serum (S) from 3 MS patients (adjusted to 10 mg IgG/l) was performed to compare IgG binding patterns to proteins B3, C5, and G4. A stronger and more focused immune response to the proteins was observed in the CSF of 10 patients analyzed in total. *P < 0.001, Fisher’s exact test.