Figure 1. Binding of natural anti-rat brain IgM in the serum of immunized and non-immunized rats as evaluated by immunoblotting. Rat brain extracts were separated by SDS PAGE and probed by immunoblotting as described in the 'Methods' section. The analysis was limited to 15 animals (n = 8 immunized; lanes I1 through I8, and n = 7 non-immunized; lanes N1 through N7) due to size constraints of the gel. A control strip with no serum is labelled “C”, and indicates the reactivity of the anti-IgM conjugate with muscle-derived antigens.