Shown is an IGHV4-39 derived, truncated IgG-VH with OCB peptides identified by mass-spectrometry in IEF gel slices “A”, “B”, “D”, “J”, and “K” (Figure 1, Table S3) in patient MS-3 CSF. Shaded in light gray are aligned AA sequences of identified OCB peptides reflective of ongoing affinity-maturation in a B cell cluster contributing to OCB production in patient MS-3. H-CDR2 and H-CDR-3 are in grey frames. Dots (․) indicate identity with the consensus sequence (top).