How specific are these S100 antibodies?

[BabcockHall]

"Protein. The S-100 brain protein studied in these experiments was purified by Moore (1965) from bovine brain, and was kindly supplied by Dr. Blake Moore.

 

Antiserum. Antibodies to bovine brain S-100 were successfully produced in rabbits after complexing the purified protein with methylated bovine serum albumin according to the method of Plescia et al. (1964) and using this complex as immunogen. The antiserum gave one major band in double-diffusion tests in agar with purified beef brain S-100 protein as antigen and, in addition, a second minor band with crude brain extract as antigen."

 

This is a passage from a 1968 paper (Kessler D, Levine L and Fasman G, Biochemistry 7:758-64). I am trying to understand one aspect of this passage, namely the identity of the second band seen when crude brain extract is being treated with the antibodies. It is regrettable that they did not provide the relative positions of the two bands in the Ouchterlony experiment, which might have been helpful in discriminating among the possibilities. The second band could conceivably be a second protein reacting with the antibodies that bind to S-100. They could also conceivably be a second brain protein reacting with a second antibody in the preparation.

 

 

Are there other interpretations besides these two? Is there any way to discriminate among these possibilities based solely on this information, or would one need to do further experiments? If anyone has some good textbook or review articles on antibody binding, I would be interested. I have a couple of older textbooks (D Freifelder, Biophysical Chemistry; TG Cooper, The Tools of Biochemistry) that are pretty good, but I would like to have more information.