The extensive cross-reaction of several syngeneic rat-anti-BP antiserums with myelin basic proteins (BP) of other species

On the average, 80–90% of the syngeneic antibodies, raised in Lewis-strain rats against Lewis-rat myelin basic protein, cross-reacted with BP from guinea pig, rabbit, beef and pig, and with the 2 basic proteins of the rat, small and large. The cross-reactions were observed in two ways: by the comparison of binding curves obtained from the reactions of experimental serums with 125I-labeled preparations of 6 basic proteins; and by absorptions of experimental serums with the 6 basic proteins bound to Sepharose-4B. The small fraction of antibodies that remained, after absorption with any of the 6 BP immunoadsorbents, did not fit any specific BP-reaction pattern; in fact, any particular adsorbent was just as efficient at removal of BP-binding activity as any other BP-Seph-4B. It appears that the systemic humoral response to syngeneic BP in the rat is restricted for the most part to the organ-specific portions (60%) of the BP molecule and not randomly extended to the remaining (40%) species-specific portions.