Comparison of S100B and S100A1 sequences to underscore similarities (normal character) and differences (in bold).

There is 94% (4 aa are different) similarity between bovine S100B used for these experiments and rat S100B. Thus, the uptake by immune cells is not due to foreign antigen sequence. Same considerations can be made for human S100A1 used as a tracer, since the human protein used shared 96% identity with rat protein.